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 "4.91"
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"
439 .row &_openssl.txt_& "installing a current OpenSSL release"
442 The main specification and the specification of the filtering language are also
443 available in other formats (HTML, PostScript, PDF, and Texinfo). Section
444 &<<SECTavail>>& below tells you how to get hold of these.
448 .section "FTP and web sites" "SECID2"
451 The primary site for Exim source distributions is the &%exim.org%& FTP site,
452 available over HTTPS, HTTP and FTP. These services, and the &%exim.org%&
453 website, are hosted at the University of Cambridge.
457 As well as Exim distribution tar files, the Exim web site contains a number of
458 differently formatted versions of the documentation. A recent addition to the
459 online information is the Exim wiki (&url(http://wiki.exim.org)),
460 which contains what used to be a separate FAQ, as well as various other
461 examples, tips, and know-how that have been contributed by Exim users.
462 The wiki site should always redirect to the correct place, which is currently
463 provided by GitHub, and is open to editing by anyone with a GitHub account.
466 An Exim Bugzilla exists at &url(https://bugs.exim.org). You can use
467 this to report bugs, and also to add items to the wish list. Please search
468 first to check that you are not duplicating a previous entry.
469 Please do not ask for configuration help in the bug-tracker.
472 .section "Mailing lists" "SECID3"
473 .cindex "mailing lists" "for Exim users"
474 The following Exim mailing lists exist:
477 .row &'exim-announce@exim.org'& "Moderated, low volume announcements list"
478 .row &'exim-users@exim.org'& "General discussion list"
479 .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc."
480 .row &'exim-cvs@exim.org'& "Automated commit messages from the VCS"
483 You can subscribe to these lists, change your existing subscriptions, and view
484 or search the archives via the mailing lists link on the Exim home page.
485 .cindex "Debian" "mailing list for"
486 If you are using a Debian distribution of Exim, you may wish to subscribe to
487 the Debian-specific mailing list &'pkg-exim4-users@lists.alioth.debian.org'&
490 &url(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 "Bug reports" "SECID5"
496 .cindex "bug reports"
497 .cindex "reporting bugs"
498 Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported
499 via the Bugzilla (&url(https://bugs.exim.org)). However, if you are unsure
500 whether some behaviour is a bug or not, the best thing to do is to post a
501 message to the &'exim-dev'& mailing list and have it discussed.
505 .section "Where to find the Exim distribution" "SECTavail"
507 .cindex "HTTPS download site"
508 .cindex "distribution" "ftp site"
509 .cindex "distribution" "https site"
510 The master distribution site for the Exim distribution is
512 &*https://downloads.exim.org/*&
514 The service is available over HTTPS, HTTP and FTP.
515 We encourage people to migrate to HTTPS.
517 The content served at &'https://downloads.exim.org/'& is identical to the
518 content served at &'https://ftp.exim.org/pub/exim'& and
519 &'ftp://ftp.exim.org/pub/exim'&.
521 If accessing via a hostname containing &'ftp'&, then the file references that
522 follow are relative to the &_exim_& directories at these sites.
523 If accessing via the hostname &'downloads'& then the subdirectories described
524 here are top-level directories.
526 There are now quite a number of independent mirror sites around
527 the world. Those that I know about are listed in the file called &_Mirrors_&.
529 Within the top exim directory there are subdirectories called &_exim3_& (for
530 previous Exim 3 distributions), &_exim4_& (for the latest Exim 4
531 distributions), and &_Testing_& for testing versions. In the &_exim4_&
532 subdirectory, the current release can always be found in files called
536 &_exim-n.nn.tar.bz2_&
538 where &'n.nn'& is the highest such version number in the directory. The three
539 files contain identical data; the only difference is the type of compression.
540 The &_.xz_& file is usually the smallest, while the &_.gz_& file is the
541 most portable to old systems.
543 .cindex "distribution" "signing details"
544 .cindex "distribution" "public key"
545 .cindex "public key for signed distribution"
546 The distributions will be PGP signed by an individual key of the Release
547 Coordinator. This key will have a uid containing an email address in the
548 &'exim.org'& domain and will have signatures from other people, including
549 other Exim maintainers. We expect that the key will be in the "strong set" of
550 PGP keys. There should be a trust path to that key from Nigel Metheringham's
551 PGP key, a version of which can be found in the release directory in the file
552 &_nigel-pubkey.asc_&. All keys used will be available in public keyserver pools,
553 such as &'pool.sks-keyservers.net'&.
555 At time of last update, releases were being made by Jeremy Harris and signed
556 with key &'0xBCE58C8CE41F32DF'&. Other recent keys used for signing are those
557 of Heiko Schlittermann, &'0x26101B62F69376CE'&,
558 and of Phil Pennock, &'0x4D1E900E14C1CC04'&.
560 The signatures for the tar bundles are in:
562 &_exim-n.nn.tar.xz.asc_&
563 &_exim-n.nn.tar.gz.asc_&
564 &_exim-n.nn.tar.bz2.asc_&
566 For each released version, the log of changes is made separately available in a
567 separate file in the directory &_ChangeLogs_& so that it is possible to
568 find out what has changed without having to download the entire distribution.
570 .cindex "documentation" "available formats"
571 The main distribution contains ASCII versions of this specification and other
572 documentation; other formats of the documents are available in separate files
573 inside the &_exim4_& directory of the FTP site:
575 &_exim-html-n.nn.tar.gz_&
576 &_exim-pdf-n.nn.tar.gz_&
577 &_exim-postscript-n.nn.tar.gz_&
578 &_exim-texinfo-n.nn.tar.gz_&
580 These tar files contain only the &_doc_& directory, not the complete
581 distribution, and are also available in &_.bz2_& and &_.xz_& forms.
584 .section "Limitations" "SECID6"
586 .cindex "limitations of Exim"
587 .cindex "bang paths" "not handled by Exim"
588 Exim is designed for use as an Internet MTA, and therefore handles addresses in
589 RFC 2822 domain format only. It cannot handle UUCP &"bang paths"&, though
590 simple two-component bang paths can be converted by a straightforward rewriting
591 configuration. This restriction does not prevent Exim from being interfaced to
592 UUCP as a transport mechanism, provided that domain addresses are used.
594 .cindex "domainless addresses"
595 .cindex "address" "without domain"
596 Exim insists that every address it handles has a domain attached. For incoming
597 local messages, domainless addresses are automatically qualified with a
598 configured domain value. Configuration options specify from which remote
599 systems unqualified addresses are acceptable. These are then qualified on
602 .cindex "transport" "external"
603 .cindex "external transports"
604 The only external transport mechanisms that are currently implemented are SMTP
605 and LMTP over a TCP/IP network (including support for IPv6). However, a pipe
606 transport is available, and there are facilities for writing messages to files
607 and pipes, optionally in &'batched SMTP'& format; these facilities can be used
608 to send messages to other transport mechanisms such as UUCP, provided they can
609 handle domain-style addresses. Batched SMTP input is also catered for.
611 Exim is not designed for storing mail for dial-in hosts. When the volumes of
612 such mail are large, it is better to get the messages &"delivered"& into files
613 (that is, off Exim's queue) and subsequently passed on to the dial-in hosts by
616 Although Exim does have basic facilities for scanning incoming messages, these
617 are not comprehensive enough to do full virus or spam scanning. Such operations
618 are best carried out using additional specialized software packages. If you
619 compile Exim with the content-scanning extension, straightforward interfaces to
620 a number of common scanners are provided.
624 .section "Run time configuration" "SECID7"
625 Exim's run time configuration is held in a single text file that is divided
626 into a number of sections. The entries in this file consist of keywords and
627 values, in the style of Smail 3 configuration files. A default configuration
628 file which is suitable for simple online installations is provided in the
629 distribution, and is described in chapter &<<CHAPdefconfil>>& below.
632 .section "Calling interface" "SECID8"
633 .cindex "Sendmail compatibility" "command line interface"
634 Like many MTAs, Exim has adopted the Sendmail command line interface so that it
635 can be a straight replacement for &_/usr/lib/sendmail_& or
636 &_/usr/sbin/sendmail_& when sending mail, but you do not need to know anything
637 about Sendmail in order to run Exim. For actions other than sending messages,
638 Sendmail-compatible options also exist, but those that produce output (for
639 example, &%-bp%&, which lists the messages on the queue) do so in Exim's own
640 format. There are also some additional options that are compatible with Smail
641 3, and some further options that are new to Exim. Chapter &<<CHAPcommandline>>&
642 documents all Exim's command line options. This information is automatically
643 made into the man page that forms part of the Exim distribution.
645 Control of messages on the queue can be done via certain privileged command
646 line options. There is also an optional monitor program called &'eximon'&,
647 which displays current information in an X window, and which contains a menu
648 interface to Exim's command line administration options.
652 .section "Terminology" "SECID9"
653 .cindex "terminology definitions"
654 .cindex "body of message" "definition of"
655 The &'body'& of a message is the actual data that the sender wants to transmit.
656 It is the last part of a message, and is separated from the &'header'& (see
657 below) by a blank line.
659 .cindex "bounce message" "definition of"
660 When a message cannot be delivered, it is normally returned to the sender in a
661 delivery failure message or a &"non-delivery report"& (NDR). The term
662 &'bounce'& is commonly used for this action, and the error reports are often
663 called &'bounce messages'&. This is a convenient shorthand for &"delivery
664 failure error report"&. Such messages have an empty sender address in the
665 message's &'envelope'& (see below) to ensure that they cannot themselves give
666 rise to further bounce messages.
668 The term &'default'& appears frequently in this manual. It is used to qualify a
669 value which is used in the absence of any setting in the configuration. It may
670 also qualify an action which is taken unless a configuration setting specifies
673 The term &'defer'& is used when the delivery of a message to a specific
674 destination cannot immediately take place for some reason (a remote host may be
675 down, or a user's local mailbox may be full). Such deliveries are &'deferred'&
678 The word &'domain'& is sometimes used to mean all but the first component of a
679 host's name. It is &'not'& used in that sense here, where it normally refers to
680 the part of an email address following the @ sign.
682 .cindex "envelope, definition of"
683 .cindex "sender" "definition of"
684 A message in transit has an associated &'envelope'&, as well as a header and a
685 body. The envelope contains a sender address (to which bounce messages should
686 be delivered), and any number of recipient addresses. References to the
687 sender or the recipients of a message usually mean the addresses in the
688 envelope. An MTA uses these addresses for delivery, and for returning bounce
689 messages, not the addresses that appear in the header lines.
691 .cindex "message" "header, definition of"
692 .cindex "header section" "definition of"
693 The &'header'& of a message is the first part of a message's text, consisting
694 of a number of lines, each of which has a name such as &'From:'&, &'To:'&,
695 &'Subject:'&, etc. Long header lines can be split over several text lines by
696 indenting the continuations. The header is separated from the body by a blank
699 .cindex "local part" "definition of"
700 .cindex "domain" "definition of"
701 The term &'local part'&, which is taken from RFC 2822, is used to refer to that
702 part of an email address that precedes the @ sign. The part that follows the
703 @ sign is called the &'domain'& or &'mail domain'&.
705 .cindex "local delivery" "definition of"
706 .cindex "remote delivery, definition of"
707 The terms &'local delivery'& and &'remote delivery'& are used to distinguish
708 delivery to a file or a pipe on the local host from delivery by SMTP over
709 TCP/IP to another host. As far as Exim is concerned, all hosts other than the
710 host it is running on are &'remote'&.
712 .cindex "return path" "definition of"
713 &'Return path'& is another name that is used for the sender address in a
716 .cindex "queue" "definition of"
717 The term &'queue'& is used to refer to the set of messages awaiting delivery,
718 because this term is in widespread use in the context of MTAs. However, in
719 Exim's case the reality is more like a pool than a queue, because there is
720 normally no ordering of waiting messages.
722 .cindex "queue runner" "definition of"
723 The term &'queue runner'& is used to describe a process that scans the queue
724 and attempts to deliver those messages whose retry times have come. This term
725 is used by other MTAs, and also relates to the command &%runq%&, but in Exim
726 the waiting messages are normally processed in an unpredictable order.
728 .cindex "spool directory" "definition of"
729 The term &'spool directory'& is used for a directory in which Exim keeps the
730 messages on its queue &-- that is, those that it is in the process of
731 delivering. This should not be confused with the directory in which local
732 mailboxes are stored, which is called a &"spool directory"& by some people. In
733 the Exim documentation, &"spool"& is always used in the first sense.
740 . ////////////////////////////////////////////////////////////////////////////
741 . ////////////////////////////////////////////////////////////////////////////
743 .chapter "Incorporated code" "CHID2"
744 .cindex "incorporated code"
745 .cindex "regular expressions" "library"
748 A number of pieces of external code are included in the Exim distribution.
751 Regular expressions are supported in the main Exim program and in the
752 Exim monitor using the freely-distributable PCRE library, copyright
753 © University of Cambridge. The source to PCRE is no longer shipped with
754 Exim, so you will need to use the version of PCRE shipped with your system,
755 or obtain and install the full version of the library from
756 &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre).
758 .cindex "cdb" "acknowledgment"
759 Support for the cdb (Constant DataBase) lookup method is provided by code
760 contributed by Nigel Metheringham of (at the time he contributed it) Planet
761 Online Ltd. The implementation is completely contained within the code of Exim.
762 It does not link against an external cdb library. The code contains the
763 following statements:
766 Copyright © 1998 Nigel Metheringham, Planet Online Ltd
768 This program is free software; you can redistribute it and/or modify it under
769 the terms of the GNU General Public License as published by the Free Software
770 Foundation; either version 2 of the License, or (at your option) any later
772 This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information,
773 the spec and sample code for cdb can be obtained from
774 &url(http://www.pobox.com/~djb/cdb.html). This implementation borrows
775 some code from Dan Bernstein's implementation (which has no license
776 restrictions applied to it).
779 .cindex "SPA authentication"
780 .cindex "Samba project"
781 .cindex "Microsoft Secure Password Authentication"
782 Client support for Microsoft's &'Secure Password Authentication'& is provided
783 by code contributed by Marc Prud'hommeaux. Server support was contributed by
784 Tom Kistner. This includes code taken from the Samba project, which is released
788 .cindex "&'pwcheck'& daemon"
789 .cindex "&'pwauthd'& daemon"
790 Support for calling the Cyrus &'pwcheck'& and &'saslauthd'& daemons is provided
791 by code taken from the Cyrus-SASL library and adapted by Alexander S.
792 Sabourenkov. The permission notice appears below, in accordance with the
793 conditions expressed therein.
796 Copyright © 2001 Carnegie Mellon University. All rights reserved.
798 Redistribution and use in source and binary forms, with or without
799 modification, are permitted provided that the following conditions
803 Redistributions of source code must retain the above copyright
804 notice, this list of conditions and the following disclaimer.
806 Redistributions in binary form must reproduce the above copyright
807 notice, this list of conditions and the following disclaimer in
808 the documentation and/or other materials provided with the
811 The name &"Carnegie Mellon University"& must not be used to
812 endorse or promote products derived from this software without
813 prior written permission. For permission or any other legal
814 details, please contact
816 Office of Technology Transfer
817 Carnegie Mellon University
819 Pittsburgh, PA 15213-3890
820 (412) 268-4387, fax: (412) 268-7395
821 tech-transfer@andrew.cmu.edu
824 Redistributions of any form whatsoever must retain the following
827 &"This product includes software developed by Computing Services
828 at Carnegie Mellon University (&url(http://www.cmu.edu/computing/)."&
830 CARNEGIE MELLON UNIVERSITY DISCLAIMS ALL WARRANTIES WITH REGARD TO
831 THIS SOFTWARE, INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
832 AND FITNESS, IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY BE LIABLE
833 FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
834 WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN
835 AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING
836 OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
841 .cindex "Exim monitor" "acknowledgment"
844 The Exim Monitor program, which is an X-Window application, includes
845 modified versions of the Athena StripChart and TextPop widgets.
846 This code is copyright by DEC and MIT, and their permission notice appears
847 below, in accordance with the conditions expressed therein.
850 Copyright 1987, 1988 by Digital Equipment Corporation, Maynard, Massachusetts,
851 and the Massachusetts Institute of Technology, Cambridge, Massachusetts.
855 Permission to use, copy, modify, and distribute this software and its
856 documentation for any purpose and without fee is hereby granted,
857 provided that the above copyright notice appear in all copies and that
858 both that copyright notice and this permission notice appear in
859 supporting documentation, and that the names of Digital or MIT not be
860 used in advertising or publicity pertaining to distribution of the
861 software without specific, written prior permission.
863 DIGITAL DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
864 ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
865 DIGITAL BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
866 ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
867 WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
868 ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
873 .cindex "opendmarc" "acknowledgment"
874 The DMARC implementation uses the OpenDMARC library which is Copyrighted by
875 The Trusted Domain Project. Portions of Exim source which use OpenDMARC
876 derived code are indicated in the respective source files. The full OpenDMARC
877 license is provided in the LICENSE.opendmarc file contained in the distributed
881 Many people have contributed code fragments, some large, some small, that were
882 not covered by any specific licence requirements. It is assumed that the
883 contributors are happy to see their code incorporated into Exim under the GPL.
890 . ////////////////////////////////////////////////////////////////////////////
891 . ////////////////////////////////////////////////////////////////////////////
893 .chapter "How Exim receives and delivers mail" "CHID11" &&&
894 "Receiving and delivering mail"
897 .section "Overall philosophy" "SECID10"
898 .cindex "design philosophy"
899 Exim is designed to work efficiently on systems that are permanently connected
900 to the Internet and are handling a general mix of mail. In such circumstances,
901 most messages can be delivered immediately. Consequently, Exim does not
902 maintain independent queues of messages for specific domains or hosts, though
903 it does try to send several messages in a single SMTP connection after a host
904 has been down, and it also maintains per-host retry information.
907 .section "Policy control" "SECID11"
908 .cindex "policy control" "overview"
909 Policy controls are now an important feature of MTAs that are connected to the
910 Internet. Perhaps their most important job is to stop MTAs being abused as
911 &"open relays"& by misguided individuals who send out vast amounts of
912 unsolicited junk, and want to disguise its source. Exim provides flexible
913 facilities for specifying policy controls on incoming mail:
916 .cindex "&ACL;" "introduction"
917 Exim 4 (unlike previous versions of Exim) implements policy controls on
918 incoming mail by means of &'Access Control Lists'& (ACLs). Each list is a
919 series of statements that may either grant or deny access. ACLs can be used at
920 several places in the SMTP dialogue while receiving a message from a remote
921 host. However, the most common places are after each RCPT command, and at the
922 very end of the message. The sysadmin can specify conditions for accepting or
923 rejecting individual recipients or the entire message, respectively, at these
924 two points (see chapter &<<CHAPACL>>&). Denial of access results in an SMTP
927 An ACL is also available for locally generated, non-SMTP messages. In this
928 case, the only available actions are to accept or deny the entire message.
930 When Exim is compiled with the content-scanning extension, facilities are
931 provided in the ACL mechanism for passing the message to external virus and/or
932 spam scanning software. The result of such a scan is passed back to the ACL,
933 which can then use it to decide what to do with the message.
935 When a message has been received, either from a remote host or from the local
936 host, but before the final acknowledgment has been sent, a locally supplied C
937 function called &[local_scan()]& can be run to inspect the message and decide
938 whether to accept it or not (see chapter &<<CHAPlocalscan>>&). If the message
939 is accepted, the list of recipients can be modified by the function.
941 Using the &[local_scan()]& mechanism is another way of calling external scanner
942 software. The &%SA-Exim%& add-on package works this way. It does not require
943 Exim to be compiled with the content-scanning extension.
945 After a message has been accepted, a further checking mechanism is available in
946 the form of the &'system filter'& (see chapter &<<CHAPsystemfilter>>&). This
947 runs at the start of every delivery process.
952 .section "User filters" "SECID12"
953 .cindex "filter" "introduction"
954 .cindex "Sieve filter"
955 In a conventional Exim configuration, users are able to run private filters by
956 setting up appropriate &_.forward_& files in their home directories. See
957 chapter &<<CHAPredirect>>& (about the &(redirect)& router) for the
958 configuration needed to support this, and the separate document entitled
959 &'Exim's interfaces to mail filtering'& for user details. Two different kinds
960 of filtering are available:
963 Sieve filters are written in the standard filtering language that is defined
966 Exim filters are written in a syntax that is unique to Exim, but which is more
967 powerful than Sieve, which it pre-dates.
970 User filters are run as part of the routing process, described below.
974 .section "Message identification" "SECTmessiden"
975 .cindex "message ids" "details of format"
976 .cindex "format" "of message id"
977 .cindex "id of message"
982 Every message handled by Exim is given a &'message id'& which is sixteen
983 characters long. It is divided into three parts, separated by hyphens, for
984 example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits,
985 normally encoding numbers in base 62. However, in the Darwin operating
986 system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36
987 (avoiding the use of lower case letters) is used instead, because the message
988 id is used to construct file names, and the names of files in those systems are
989 not always case-sensitive.
991 .cindex "pid (process id)" "re-use of"
992 The detail of the contents of the message id have changed as Exim has evolved.
993 Earlier versions relied on the operating system not re-using a process id (pid)
994 within one second. On modern operating systems, this assumption can no longer
995 be made, so the algorithm had to be changed. To retain backward compatibility,
996 the format of the message id was retained, which is why the following rules are
1000 The first six characters of the message id are the time at which the message
1001 started to be received, to a granularity of one second. That is, this field
1002 contains the number of seconds since the start of the epoch (the normal Unix
1003 way of representing the date and time of day).
1005 After the first hyphen, the next six characters are the id of the process that
1006 received the message.
1008 There are two different possibilities for the final two characters:
1010 .oindex "&%localhost_number%&"
1011 If &%localhost_number%& is not set, this value is the fractional part of the
1012 time of reception, normally in units of 1/2000 of a second, but for systems
1013 that must use base 36 instead of base 62 (because of case-insensitive file
1014 systems), the units are 1/1000 of a second.
1016 If &%localhost_number%& is set, it is multiplied by 200 (100) and added to
1017 the fractional part of the time, which in this case is in units of 1/200
1018 (1/100) of a second.
1022 After a message has been received, Exim waits for the clock to tick at the
1023 appropriate resolution before proceeding, so that if another message is
1024 received by the same process, or by another process with the same (re-used)
1025 pid, it is guaranteed that the time will be different. In most cases, the clock
1026 will already have ticked while the message was being received.
1029 .section "Receiving mail" "SECID13"
1030 .cindex "receiving mail"
1031 .cindex "message" "reception"
1032 The only way Exim can receive mail from another host is using SMTP over
1033 TCP/IP, in which case the sender and recipient addresses are transferred using
1034 SMTP commands. However, from a locally running process (such as a user's MUA),
1035 there are several possibilities:
1038 If the process runs Exim with the &%-bm%& option, the message is read
1039 non-interactively (usually via a pipe), with the recipients taken from the
1040 command line, or from the body of the message if &%-t%& is also used.
1042 If the process runs Exim with the &%-bS%& option, the message is also read
1043 non-interactively, but in this case the recipients are listed at the start of
1044 the message in a series of SMTP RCPT commands, terminated by a DATA
1045 command. This is so-called &"batch SMTP"& format,
1046 but it isn't really SMTP. The SMTP commands are just another way of passing
1047 envelope addresses in a non-interactive submission.
1049 If the process runs Exim with the &%-bs%& option, the message is read
1050 interactively, using the SMTP protocol. A two-way pipe is normally used for
1051 passing data between the local process and the Exim process.
1052 This is &"real"& SMTP and is handled in the same way as SMTP over TCP/IP. For
1053 example, the ACLs for SMTP commands are used for this form of submission.
1055 A local process may also make a TCP/IP call to the host's loopback address
1056 (127.0.0.1) or any other of its IP addresses. When receiving messages, Exim
1057 does not treat the loopback address specially. It treats all such connections
1058 in the same way as connections from other hosts.
1062 .cindex "message sender, constructed by Exim"
1063 .cindex "sender" "constructed by Exim"
1064 In the three cases that do not involve TCP/IP, the sender address is
1065 constructed from the login name of the user that called Exim and a default
1066 qualification domain (which can be set by the &%qualify_domain%& configuration
1067 option). For local or batch SMTP, a sender address that is passed using the
1068 SMTP MAIL command is ignored. However, the system administrator may allow
1069 certain users (&"trusted users"&) to specify a different sender address
1070 unconditionally, or all users to specify certain forms of different sender
1071 address. The &%-f%& option or the SMTP MAIL command is used to specify these
1072 different addresses. See section &<<SECTtrustedadmin>>& for details of trusted
1073 users, and the &%untrusted_set_sender%& option for a way of allowing untrusted
1074 users to change sender addresses.
1076 Messages received by either of the non-interactive mechanisms are subject to
1077 checking by the non-SMTP ACL, if one is defined. Messages received using SMTP
1078 (either over TCP/IP, or interacting with a local process) can be checked by a
1079 number of ACLs that operate at different times during the SMTP session. Either
1080 individual recipients, or the entire message, can be rejected if local policy
1081 requirements are not met. The &[local_scan()]& function (see chapter
1082 &<<CHAPlocalscan>>&) is run for all incoming messages.
1084 Exim can be configured not to start a delivery process when a message is
1085 received; this can be unconditional, or depend on the number of incoming SMTP
1086 connections or the system load. In these situations, new messages wait on the
1087 queue until a queue runner process picks them up. However, in standard
1088 configurations under normal conditions, delivery is started as soon as a
1089 message is received.
1095 .section "Handling an incoming message" "SECID14"
1096 .cindex "spool directory" "files that hold a message"
1097 .cindex "file" "how a message is held"
1098 When Exim accepts a message, it writes two files in its spool directory. The
1099 first contains the envelope information, the current status of the message, and
1100 the header lines, and the second contains the body of the message. The names of
1101 the two spool files consist of the message id, followed by &`-H`& for the
1102 file containing the envelope and header, and &`-D`& for the data file.
1104 .cindex "spool directory" "&_input_& sub-directory"
1105 By default all these message files are held in a single directory called
1106 &_input_& inside the general Exim spool directory. Some operating systems do
1107 not perform very well if the number of files in a directory gets large; to
1108 improve performance in such cases, the &%split_spool_directory%& option can be
1109 used. This causes Exim to split up the input files into 62 sub-directories
1110 whose names are single letters or digits. When this is done, the queue is
1111 processed one sub-directory at a time instead of all at once, which can improve
1112 overall performance even when there are not enough files in each directory to
1113 affect file system performance.
1115 The envelope information consists of the address of the message's sender and
1116 the addresses of the recipients. This information is entirely separate from
1117 any addresses contained in the header lines. The status of the message includes
1118 a list of recipients who have already received the message. The format of the
1119 first spool file is described in chapter &<<CHAPspool>>&.
1121 .cindex "rewriting" "addresses"
1122 Address rewriting that is specified in the rewrite section of the configuration
1123 (see chapter &<<CHAPrewrite>>&) is done once and for all on incoming addresses,
1124 both in the header lines and the envelope, at the time the message is accepted.
1125 If during the course of delivery additional addresses are generated (for
1126 example, via aliasing), these new addresses are rewritten as soon as they are
1127 generated. At the time a message is actually delivered (transported) further
1128 rewriting can take place; because this is a transport option, it can be
1129 different for different forms of delivery. It is also possible to specify the
1130 addition or removal of certain header lines at the time the message is
1131 delivered (see chapters &<<CHAProutergeneric>>& and
1132 &<<CHAPtransportgeneric>>&).
1136 .section "Life of a message" "SECID15"
1137 .cindex "message" "life of"
1138 .cindex "message" "frozen"
1139 A message remains in the spool directory until it is completely delivered to
1140 its recipients or to an error address, or until it is deleted by an
1141 administrator or by the user who originally created it. In cases when delivery
1142 cannot proceed &-- for example, when a message can neither be delivered to its
1143 recipients nor returned to its sender, the message is marked &"frozen"& on the
1144 spool, and no more deliveries are attempted.
1146 .cindex "frozen messages" "thawing"
1147 .cindex "message" "thawing frozen"
1148 An administrator can &"thaw"& such messages when the problem has been
1149 corrected, and can also freeze individual messages by hand if necessary. In
1150 addition, an administrator can force a delivery error, causing a bounce message
1153 .oindex "&%timeout_frozen_after%&"
1154 .oindex "&%ignore_bounce_errors_after%&"
1155 There are options called &%ignore_bounce_errors_after%& and
1156 &%timeout_frozen_after%&, which discard frozen messages after a certain time.
1157 The first applies only to frozen bounces, the second to any frozen messages.
1159 .cindex "message" "log file for"
1160 .cindex "log" "file for each message"
1161 While Exim is working on a message, it writes information about each delivery
1162 attempt to its main log file. This includes successful, unsuccessful, and
1163 delayed deliveries for each recipient (see chapter &<<CHAPlog>>&). The log
1164 lines are also written to a separate &'message log'& file for each message.
1165 These logs are solely for the benefit of the administrator, and are normally
1166 deleted along with the spool files when processing of a message is complete.
1167 The use of individual message logs can be disabled by setting
1168 &%no_message_logs%&; this might give an improvement in performance on very busy
1171 .cindex "journal file"
1172 .cindex "file" "journal"
1173 All the information Exim itself needs to set up a delivery is kept in the first
1174 spool file, along with the header lines. When a successful delivery occurs, the
1175 address is immediately written at the end of a journal file, whose name is the
1176 message id followed by &`-J`&. At the end of a delivery run, if there are some
1177 addresses left to be tried again later, the first spool file (the &`-H`& file)
1178 is updated to indicate which these are, and the journal file is then deleted.
1179 Updating the spool file is done by writing a new file and renaming it, to
1180 minimize the possibility of data loss.
1182 Should the system or the program crash after a successful delivery but before
1183 the spool file has been updated, the journal is left lying around. The next
1184 time Exim attempts to deliver the message, it reads the journal file and
1185 updates the spool file before proceeding. This minimizes the chances of double
1186 deliveries caused by crashes.
1190 .section "Processing an address for delivery" "SECTprocaddress"
1191 .cindex "drivers" "definition of"
1192 .cindex "router" "definition of"
1193 .cindex "transport" "definition of"
1194 The main delivery processing elements of Exim are called &'routers'& and
1195 &'transports'&, and collectively these are known as &'drivers'&. Code for a
1196 number of them is provided in the source distribution, and compile-time options
1197 specify which ones are included in the binary. Run time options specify which
1198 ones are actually used for delivering messages.
1200 .cindex "drivers" "instance definition"
1201 Each driver that is specified in the run time configuration is an &'instance'&
1202 of that particular driver type. Multiple instances are allowed; for example,
1203 you can set up several different &(smtp)& transports, each with different
1204 option values that might specify different ports or different timeouts. Each
1205 instance has its own identifying name. In what follows we will normally use the
1206 instance name when discussing one particular instance (that is, one specific
1207 configuration of the driver), and the generic driver name when discussing
1208 the driver's features in general.
1210 A &'router'& is a driver that operates on an address, either determining how
1211 its delivery should happen, by assigning it to a specific transport, or
1212 converting the address into one or more new addresses (for example, via an
1213 alias file). A router may also explicitly choose to fail an address, causing it
1216 A &'transport'& is a driver that transmits a copy of the message from Exim's
1217 spool to some destination. There are two kinds of transport: for a &'local'&
1218 transport, the destination is a file or a pipe on the local host, whereas for a
1219 &'remote'& transport the destination is some other host. A message is passed
1220 to a specific transport as a result of successful routing. If a message has
1221 several recipients, it may be passed to a number of different transports.
1223 .cindex "preconditions" "definition of"
1224 An address is processed by passing it to each configured router instance in
1225 turn, subject to certain preconditions, until a router accepts the address or
1226 specifies that it should be bounced. We will describe this process in more
1227 detail shortly. First, as a simple example, we consider how each recipient
1228 address in a message is processed in a small configuration of three routers.
1230 To make this a more concrete example, it is described in terms of some actual
1231 routers, but remember, this is only an example. You can configure Exim's
1232 routers in many different ways, and there may be any number of routers in a
1235 The first router that is specified in a configuration is often one that handles
1236 addresses in domains that are not recognized specially by the local host. These
1237 are typically addresses for arbitrary domains on the Internet. A precondition
1238 is set up which looks for the special domains known to the host (for example,
1239 its own domain name), and the router is run for addresses that do &'not'&
1240 match. Typically, this is a router that looks up domains in the DNS in order to
1241 find the hosts to which this address routes. If it succeeds, the address is
1242 assigned to a suitable SMTP transport; if it does not succeed, the router is
1243 configured to fail the address.
1245 The second router is reached only when the domain is recognized as one that
1246 &"belongs"& to the local host. This router does redirection &-- also known as
1247 aliasing and forwarding. When it generates one or more new addresses from the
1248 original, each of them is routed independently from the start. Otherwise, the
1249 router may cause an address to fail, or it may simply decline to handle the
1250 address, in which case the address is passed to the next router.
1252 The final router in many configurations is one that checks to see if the
1253 address belongs to a local mailbox. The precondition may involve a check to
1254 see if the local part is the name of a login account, or it may look up the
1255 local part in a file or a database. If its preconditions are not met, or if
1256 the router declines, we have reached the end of the routers. When this happens,
1257 the address is bounced.
1261 .section "Processing an address for verification" "SECID16"
1262 .cindex "router" "for verification"
1263 .cindex "verifying address" "overview"
1264 As well as being used to decide how to deliver to an address, Exim's routers
1265 are also used for &'address verification'&. Verification can be requested as
1266 one of the checks to be performed in an ACL for incoming messages, on both
1267 sender and recipient addresses, and it can be tested using the &%-bv%& and
1268 &%-bvs%& command line options.
1270 When an address is being verified, the routers are run in &"verify mode"&. This
1271 does not affect the way the routers work, but it is a state that can be
1272 detected. By this means, a router can be skipped or made to behave differently
1273 when verifying. A common example is a configuration in which the first router
1274 sends all messages to a message-scanning program, unless they have been
1275 previously scanned. Thus, the first router accepts all addresses without any
1276 checking, making it useless for verifying. Normally, the &%no_verify%& option
1277 would be set for such a router, causing it to be skipped in verify mode.
1282 .section "Running an individual router" "SECTrunindrou"
1283 .cindex "router" "running details"
1284 .cindex "preconditions" "checking"
1285 .cindex "router" "result of running"
1286 As explained in the example above, a number of preconditions are checked before
1287 running a router. If any are not met, the router is skipped, and the address is
1288 passed to the next router. When all the preconditions on a router &'are'& met,
1289 the router is run. What happens next depends on the outcome, which is one of
1293 &'accept'&: The router accepts the address, and either assigns it to a
1294 transport, or generates one or more &"child"& addresses. Processing the
1295 original address ceases,
1296 .oindex "&%unseen%&"
1297 unless the &%unseen%& option is set on the router. This option
1298 can be used to set up multiple deliveries with different routing (for example,
1299 for keeping archive copies of messages). When &%unseen%& is set, the address is
1300 passed to the next router. Normally, however, an &'accept'& return marks the
1303 Any child addresses generated by the router are processed independently,
1304 starting with the first router by default. It is possible to change this by
1305 setting the &%redirect_router%& option to specify which router to start at for
1306 child addresses. Unlike &%pass_router%& (see below) the router specified by
1307 &%redirect_router%& may be anywhere in the router configuration.
1309 &'pass'&: The router recognizes the address, but cannot handle it itself. It
1310 requests that the address be passed to another router. By default the address
1311 is passed to the next router, but this can be changed by setting the
1312 &%pass_router%& option. However, (unlike &%redirect_router%&) the named router
1313 must be below the current router (to avoid loops).
1315 &'decline'&: The router declines to accept the address because it does not
1316 recognize it at all. By default, the address is passed to the next router, but
1317 this can be prevented by setting the &%no_more%& option. When &%no_more%& is
1318 set, all the remaining routers are skipped. In effect, &%no_more%& converts
1319 &'decline'& into &'fail'&.
1321 &'fail'&: The router determines that the address should fail, and queues it for
1322 the generation of a bounce message. There is no further processing of the
1323 original address unless &%unseen%& is set on the router.
1325 &'defer'&: The router cannot handle the address at the present time. (A
1326 database may be offline, or a DNS lookup may have timed out.) No further
1327 processing of the address happens in this delivery attempt. It is tried again
1328 next time the message is considered for delivery.
1330 &'error'&: There is some error in the router (for example, a syntax error in
1331 its configuration). The action is as for defer.
1334 If an address reaches the end of the routers without having been accepted by
1335 any of them, it is bounced as unrouteable. The default error message in this
1336 situation is &"unrouteable address"&, but you can set your own message by
1337 making use of the &%cannot_route_message%& option. This can be set for any
1338 router; the value from the last router that &"saw"& the address is used.
1340 Sometimes while routing you want to fail a delivery when some conditions are
1341 met but others are not, instead of passing the address on for further routing.
1342 You can do this by having a second router that explicitly fails the delivery
1343 when the relevant conditions are met. The &(redirect)& router has a &"fail"&
1344 facility for this purpose.
1347 .section "Duplicate addresses" "SECID17"
1348 .cindex "case of local parts"
1349 .cindex "address duplicate, discarding"
1350 .cindex "duplicate addresses"
1351 Once routing is complete, Exim scans the addresses that are assigned to local
1352 and remote transports, and discards any duplicates that it finds. During this
1353 check, local parts are treated as case-sensitive. This happens only when
1354 actually delivering a message; when testing routers with &%-bt%&, all the
1355 routed addresses are shown.
1359 .section "Router preconditions" "SECTrouprecon"
1360 .cindex "router" "preconditions, order of processing"
1361 .cindex "preconditions" "order of processing"
1362 The preconditions that are tested for each router are listed below, in the
1363 order in which they are tested. The individual configuration options are
1364 described in more detail in chapter &<<CHAProutergeneric>>&.
1367 The &%local_part_prefix%& and &%local_part_suffix%& options can specify that
1368 the local parts handled by the router may or must have certain prefixes and/or
1369 suffixes. If a mandatory affix (prefix or suffix) is not present, the router is
1370 skipped. These conditions are tested first. When an affix is present, it is
1371 removed from the local part before further processing, including the evaluation
1372 of any other conditions.
1374 Routers can be designated for use only when not verifying an address, that is,
1375 only when routing it for delivery (or testing its delivery routing). If the
1376 &%verify%& option is set false, the router is skipped when Exim is verifying an
1378 Setting the &%verify%& option actually sets two options, &%verify_sender%& and
1379 &%verify_recipient%&, which independently control the use of the router for
1380 sender and recipient verification. You can set these options directly if
1381 you want a router to be used for only one type of verification.
1382 Note that cutthrough delivery is classed as a recipient verification for this purpose.
1384 If the &%address_test%& option is set false, the router is skipped when Exim is
1385 run with the &%-bt%& option to test an address routing. This can be helpful
1386 when the first router sends all new messages to a scanner of some sort; it
1387 makes it possible to use &%-bt%& to test subsequent delivery routing without
1388 having to simulate the effect of the scanner.
1390 Routers can be designated for use only when verifying an address, as
1391 opposed to routing it for delivery. The &%verify_only%& option controls this.
1392 Again, cutthrough delivery counts as a verification.
1394 Individual routers can be explicitly skipped when running the routers to
1395 check an address given in the SMTP EXPN command (see the &%expn%& option).
1397 If the &%domains%& option is set, the domain of the address must be in the set
1398 of domains that it defines.
1400 .vindex "&$local_part_prefix$&"
1401 .vindex "&$local_part$&"
1402 .vindex "&$local_part_suffix$&"
1403 If the &%local_parts%& option is set, the local part of the address must be in
1404 the set of local parts that it defines. If &%local_part_prefix%& or
1405 &%local_part_suffix%& is in use, the prefix or suffix is removed from the local
1406 part before this check. If you want to do precondition tests on local parts
1407 that include affixes, you can do so by using a &%condition%& option (see below)
1408 that uses the variables &$local_part$&, &$local_part_prefix$&, and
1409 &$local_part_suffix$& as necessary.
1411 .vindex "&$local_user_uid$&"
1412 .vindex "&$local_user_gid$&"
1414 If the &%check_local_user%& option is set, the local part must be the name of
1415 an account on the local host. If this check succeeds, the uid and gid of the
1416 local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
1417 user's home directory is placed in &$home$&; these values can be used in the
1418 remaining preconditions.
1420 If the &%router_home_directory%& option is set, it is expanded at this point,
1421 because it overrides the value of &$home$&. If this expansion were left till
1422 later, the value of &$home$& as set by &%check_local_user%& would be used in
1423 subsequent tests. Having two different values of &$home$& in the same router
1424 could lead to confusion.
1426 If the &%senders%& option is set, the envelope sender address must be in the
1427 set of addresses that it defines.
1429 If the &%require_files%& option is set, the existence or non-existence of
1430 specified files is tested.
1432 .cindex "customizing" "precondition"
1433 If the &%condition%& option is set, it is evaluated and tested. This option
1434 uses an expanded string to allow you to set up your own custom preconditions.
1435 Expanded strings are described in chapter &<<CHAPexpand>>&.
1439 Note that &%require_files%& comes near the end of the list, so you cannot use
1440 it to check for the existence of a file in which to lookup up a domain, local
1441 part, or sender. However, as these options are all expanded, you can use the
1442 &%exists%& expansion condition to make such tests within each condition. The
1443 &%require_files%& option is intended for checking files that the router may be
1444 going to use internally, or which are needed by a specific transport (for
1445 example, &_.procmailrc_&).
1449 .section "Delivery in detail" "SECID18"
1450 .cindex "delivery" "in detail"
1451 When a message is to be delivered, the sequence of events is as follows:
1454 If a system-wide filter file is specified, the message is passed to it. The
1455 filter may add recipients to the message, replace the recipients, discard the
1456 message, cause a new message to be generated, or cause the message delivery to
1457 fail. The format of the system filter file is the same as for Exim user filter
1458 files, described in the separate document entitled &'Exim's interfaces to mail
1460 .cindex "Sieve filter" "not available for system filter"
1461 (&*Note*&: Sieve cannot be used for system filter files.)
1463 Some additional features are available in system filters &-- see chapter
1464 &<<CHAPsystemfilter>>& for details. Note that a message is passed to the system
1465 filter only once per delivery attempt, however many recipients it has. However,
1466 if there are several delivery attempts because one or more addresses could not
1467 be immediately delivered, the system filter is run each time. The filter
1468 condition &%first_delivery%& can be used to detect the first run of the system
1471 Each recipient address is offered to each configured router in turn, subject to
1472 its preconditions, until one is able to handle it. If no router can handle the
1473 address, that is, if they all decline, the address is failed. Because routers
1474 can be targeted at particular domains, several locally handled domains can be
1475 processed entirely independently of each other.
1477 .cindex "routing" "loops in"
1478 .cindex "loop" "while routing"
1479 A router that accepts an address may assign it to a local or a remote
1480 transport. However, the transport is not run at this time. Instead, the address
1481 is placed on a list for the particular transport, which will be run later.
1482 Alternatively, the router may generate one or more new addresses (typically
1483 from alias, forward, or filter files). New addresses are fed back into this
1484 process from the top, but in order to avoid loops, a router ignores any address
1485 which has an identically-named ancestor that was processed by itself.
1487 When all the routing has been done, addresses that have been successfully
1488 handled are passed to their assigned transports. When local transports are
1489 doing real local deliveries, they handle only one address at a time, but if a
1490 local transport is being used as a pseudo-remote transport (for example, to
1491 collect batched SMTP messages for transmission by some other means) multiple
1492 addresses can be handled. Remote transports can always handle more than one
1493 address at a time, but can be configured not to do so, or to restrict multiple
1494 addresses to the same domain.
1496 Each local delivery to a file or a pipe runs in a separate process under a
1497 non-privileged uid, and these deliveries are run one at a time. Remote
1498 deliveries also run in separate processes, normally under a uid that is private
1499 to Exim (&"the Exim user"&), but in this case, several remote deliveries can be
1500 run in parallel. The maximum number of simultaneous remote deliveries for any
1501 one message is set by the &%remote_max_parallel%& option.
1502 The order in which deliveries are done is not defined, except that all local
1503 deliveries happen before any remote deliveries.
1505 .cindex "queue runner"
1506 When it encounters a local delivery during a queue run, Exim checks its retry
1507 database to see if there has been a previous temporary delivery failure for the
1508 address before running the local transport. If there was a previous failure,
1509 Exim does not attempt a new delivery until the retry time for the address is
1510 reached. However, this happens only for delivery attempts that are part of a
1511 queue run. Local deliveries are always attempted when delivery immediately
1512 follows message reception, even if retry times are set for them. This makes for
1513 better behaviour if one particular message is causing problems (for example,
1514 causing quota overflow, or provoking an error in a filter file).
1516 .cindex "delivery" "retry in remote transports"
1517 Remote transports do their own retry handling, since an address may be
1518 deliverable to one of a number of hosts, each of which may have a different
1519 retry time. If there have been previous temporary failures and no host has
1520 reached its retry time, no delivery is attempted, whether in a queue run or
1521 not. See chapter &<<CHAPretry>>& for details of retry strategies.
1523 If there were any permanent errors, a bounce message is returned to an
1524 appropriate address (the sender in the common case), with details of the error
1525 for each failing address. Exim can be configured to send copies of bounce
1526 messages to other addresses.
1528 .cindex "delivery" "deferral"
1529 If one or more addresses suffered a temporary failure, the message is left on
1530 the queue, to be tried again later. Delivery of these addresses is said to be
1533 When all the recipient addresses have either been delivered or bounced,
1534 handling of the message is complete. The spool files and message log are
1535 deleted, though the message log can optionally be preserved if required.
1541 .section "Retry mechanism" "SECID19"
1542 .cindex "delivery" "retry mechanism"
1543 .cindex "retry" "description of mechanism"
1544 .cindex "queue runner"
1545 Exim's mechanism for retrying messages that fail to get delivered at the first
1546 attempt is the queue runner process. You must either run an Exim daemon that
1547 uses the &%-q%& option with a time interval to start queue runners at regular
1548 intervals, or use some other means (such as &'cron'&) to start them. If you do
1549 not arrange for queue runners to be run, messages that fail temporarily at the
1550 first attempt will remain on your queue for ever. A queue runner process works
1551 its way through the queue, one message at a time, trying each delivery that has
1552 passed its retry time.
1553 You can run several queue runners at once.
1555 Exim uses a set of configured rules to determine when next to retry the failing
1556 address (see chapter &<<CHAPretry>>&). These rules also specify when Exim
1557 should give up trying to deliver to the address, at which point it generates a
1558 bounce message. If no retry rules are set for a particular host, address, and
1559 error combination, no retries are attempted, and temporary errors are treated
1564 .section "Temporary delivery failure" "SECID20"
1565 .cindex "delivery" "temporary failure"
1566 There are many reasons why a message may not be immediately deliverable to a
1567 particular address. Failure to connect to a remote machine (because it, or the
1568 connection to it, is down) is one of the most common. Temporary failures may be
1569 detected during routing as well as during the transport stage of delivery.
1570 Local deliveries may be delayed if NFS files are unavailable, or if a mailbox
1571 is on a file system where the user is over quota. Exim can be configured to
1572 impose its own quotas on local mailboxes; where system quotas are set they will
1575 If a host is unreachable for a period of time, a number of messages may be
1576 waiting for it by the time it recovers, and sending them in a single SMTP
1577 connection is clearly beneficial. Whenever a delivery to a remote host is
1579 .cindex "hints database" "deferred deliveries"
1580 Exim makes a note in its hints database, and whenever a successful
1581 SMTP delivery has happened, it looks to see if any other messages are waiting
1582 for the same host. If any are found, they are sent over the same SMTP
1583 connection, subject to a configuration limit as to the maximum number in any
1588 .section "Permanent delivery failure" "SECID21"
1589 .cindex "delivery" "permanent failure"
1590 .cindex "bounce message" "when generated"
1591 When a message cannot be delivered to some or all of its intended recipients, a
1592 bounce message is generated. Temporary delivery failures turn into permanent
1593 errors when their timeout expires. All the addresses that fail in a given
1594 delivery attempt are listed in a single message. If the original message has
1595 many recipients, it is possible for some addresses to fail in one delivery
1596 attempt and others to fail subsequently, giving rise to more than one bounce
1597 message. The wording of bounce messages can be customized by the administrator.
1598 See chapter &<<CHAPemsgcust>>& for details.
1600 .cindex "&'X-Failed-Recipients:'& header line"
1601 Bounce messages contain an &'X-Failed-Recipients:'& header line that lists the
1602 failed addresses, for the benefit of programs that try to analyse such messages
1605 .cindex "bounce message" "recipient of"
1606 A bounce message is normally sent to the sender of the original message, as
1607 obtained from the message's envelope. For incoming SMTP messages, this is the
1608 address given in the MAIL command. However, when an address is expanded via a
1609 forward or alias file, an alternative address can be specified for delivery
1610 failures of the generated addresses. For a mailing list expansion (see section
1611 &<<SECTmailinglists>>&) it is common to direct bounce messages to the manager
1616 .section "Failures to deliver bounce messages" "SECID22"
1617 .cindex "bounce message" "failure to deliver"
1618 If a bounce message (either locally generated or received from a remote host)
1619 itself suffers a permanent delivery failure, the message is left on the queue,
1620 but it is frozen, awaiting the attention of an administrator. There are options
1621 that can be used to make Exim discard such failed messages, or to keep them
1622 for only a short time (see &%timeout_frozen_after%& and
1623 &%ignore_bounce_errors_after%&).
1629 . ////////////////////////////////////////////////////////////////////////////
1630 . ////////////////////////////////////////////////////////////////////////////
1632 .chapter "Building and installing Exim" "CHID3"
1633 .scindex IIDbuex "building Exim"
1635 .section "Unpacking" "SECID23"
1636 Exim is distributed as a gzipped or bzipped tar file which, when unpacked,
1637 creates a directory with the name of the current release (for example,
1638 &_exim-&version()_&) into which the following files are placed:
1641 .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments"
1642 .irow &_CHANGES_& "contains a reference to where changes are &&&
1644 .irow &_LICENCE_& "the GNU General Public Licence"
1645 .irow &_Makefile_& "top-level make file"
1646 .irow &_NOTICE_& "conditions for the use of Exim"
1647 .irow &_README_& "list of files, directories and simple build &&&
1651 Other files whose names begin with &_README_& may also be present. The
1652 following subdirectories are created:
1655 .irow &_Local_& "an empty directory for local configuration files"
1656 .irow &_OS_& "OS-specific files"
1657 .irow &_doc_& "documentation files"
1658 .irow &_exim_monitor_& "source files for the Exim monitor"
1659 .irow &_scripts_& "scripts used in the build process"
1660 .irow &_src_& "remaining source files"
1661 .irow &_util_& "independent utilities"
1664 The main utility programs are contained in the &_src_& directory, and are built
1665 with the Exim binary. The &_util_& directory contains a few optional scripts
1666 that may be useful to some sites.
1669 .section "Multiple machine architectures and operating systems" "SECID24"
1670 .cindex "building Exim" "multiple OS/architectures"
1671 The building process for Exim is arranged to make it easy to build binaries for
1672 a number of different architectures and operating systems from the same set of
1673 source files. Compilation does not take place in the &_src_& directory.
1674 Instead, a &'build directory'& is created for each architecture and operating
1676 .cindex "symbolic link" "to build directory"
1677 Symbolic links to the sources are installed in this directory, which is where
1678 the actual building takes place. In most cases, Exim can discover the machine
1679 architecture and operating system for itself, but the defaults can be
1680 overridden if necessary.
1681 .cindex compiler requirements
1682 .cindex compiler version
1683 A C99-capable compiler will be required for the build.
1686 .section "PCRE library" "SECTpcre"
1687 .cindex "PCRE library"
1688 Exim no longer has an embedded PCRE library as the vast majority of
1689 modern systems include PCRE as a system library, although you may need
1690 to install the PCRE or PCRE development package for your operating
1691 system. If your system has a normal PCRE installation the Exim build
1692 process will need no further configuration. If the library or the
1693 headers are in an unusual location you will need to either set the PCRE_LIBS
1694 and INCLUDE directives appropriately,
1695 or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command.
1696 If your operating system has no
1697 PCRE support then you will need to obtain and build the current PCRE
1698 from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/).
1699 More information on PCRE is available at &url(http://www.pcre.org/).
1701 .section "DBM libraries" "SECTdb"
1702 .cindex "DBM libraries" "discussion of"
1703 .cindex "hints database" "DBM files used for"
1704 Even if you do not use any DBM files in your configuration, Exim still needs a
1705 DBM library in order to operate, because it uses indexed files for its hints
1706 databases. Unfortunately, there are a number of DBM libraries in existence, and
1707 different operating systems often have different ones installed.
1709 .cindex "Solaris" "DBM library for"
1710 .cindex "IRIX, DBM library for"
1711 .cindex "BSD, DBM library for"
1712 .cindex "Linux, DBM library for"
1713 If you are using Solaris, IRIX, one of the modern BSD systems, or a modern
1714 Linux distribution, the DBM configuration should happen automatically, and you
1715 may be able to ignore this section. Otherwise, you may have to learn more than
1716 you would like about DBM libraries from what follows.
1718 .cindex "&'ndbm'& DBM library"
1719 Licensed versions of Unix normally contain a library of DBM functions operating
1720 via the &'ndbm'& interface, and this is what Exim expects by default. Free
1721 versions of Unix seem to vary in what they contain as standard. In particular,
1722 some early versions of Linux have no default DBM library, and different
1723 distributors have chosen to bundle different libraries with their packaged
1724 versions. However, the more recent releases seem to have standardized on the
1725 Berkeley DB library.
1727 Different DBM libraries have different conventions for naming the files they
1728 use. When a program opens a file called &_dbmfile_&, there are several
1732 A traditional &'ndbm'& implementation, such as that supplied as part of
1733 Solaris, operates on two files called &_dbmfile.dir_& and &_dbmfile.pag_&.
1735 .cindex "&'gdbm'& DBM library"
1736 The GNU library, &'gdbm'&, operates on a single file. If used via its &'ndbm'&
1737 compatibility interface it makes two different hard links to it with names
1738 &_dbmfile.dir_& and &_dbmfile.pag_&, but if used via its native interface, the
1739 file name is used unmodified.
1741 .cindex "Berkeley DB library"
1742 The Berkeley DB package, if called via its &'ndbm'& compatibility interface,
1743 operates on a single file called &_dbmfile.db_&, but otherwise looks to the
1744 programmer exactly the same as the traditional &'ndbm'& implementation.
1746 If the Berkeley package is used in its native mode, it operates on a single
1747 file called &_dbmfile_&; the programmer's interface is somewhat different to
1748 the traditional &'ndbm'& interface.
1750 To complicate things further, there are several very different versions of the
1751 Berkeley DB package. Version 1.85 was stable for a very long time, releases
1752 2.&'x'& and 3.&'x'& were current for a while, but the latest versions are now
1753 numbered 4.&'x'&. Maintenance of some of the earlier releases has ceased. All
1754 versions of Berkeley DB can be obtained from
1755 &url(http://www.sleepycat.com/).
1757 .cindex "&'tdb'& DBM library"
1758 Yet another DBM library, called &'tdb'&, is available from
1759 &url(http://download.sourceforge.net/tdb). It has its own interface, and also
1760 operates on a single file.
1764 .cindex "DBM libraries" "configuration for building"
1765 Exim and its utilities can be compiled to use any of these interfaces. In order
1766 to use any version of the Berkeley DB package in native mode, you must set
1767 USE_DB in an appropriate configuration file (typically
1768 &_Local/Makefile_&). For example:
1772 Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An
1773 error is diagnosed if you set more than one of these.
1775 At the lowest level, the build-time configuration sets none of these options,
1776 thereby assuming an interface of type (1). However, some operating system
1777 configuration files (for example, those for the BSD operating systems and
1778 Linux) assume type (4) by setting USE_DB as their default, and the
1779 configuration files for Cygwin set USE_GDBM. Anything you set in
1780 &_Local/Makefile_&, however, overrides these system defaults.
1782 As well as setting USE_DB, USE_GDBM, or USE_TDB, it may also be
1783 necessary to set DBMLIB, to cause inclusion of the appropriate library, as
1784 in one of these lines:
1789 Settings like that will work if the DBM library is installed in the standard
1790 place. Sometimes it is not, and the library's header file may also not be in
1791 the default path. You may need to set INCLUDE to specify where the header
1792 file is, and to specify the path to the library more fully in DBMLIB, as in
1795 INCLUDE=-I/usr/local/include/db-4.1
1796 DBMLIB=/usr/local/lib/db-4.1/libdb.a
1798 There is further detailed discussion about the various DBM libraries in the
1799 file &_doc/dbm.discuss.txt_& in the Exim distribution.
1803 .section "Pre-building configuration" "SECID25"
1804 .cindex "building Exim" "pre-building configuration"
1805 .cindex "configuration for building Exim"
1806 .cindex "&_Local/Makefile_&"
1807 .cindex "&_src/EDITME_&"
1808 Before building Exim, a local configuration file that specifies options
1809 independent of any operating system has to be created with the name
1810 &_Local/Makefile_&. A template for this file is supplied as the file
1811 &_src/EDITME_&, and it contains full descriptions of all the option settings
1812 therein. These descriptions are therefore not repeated here. If you are
1813 building Exim for the first time, the simplest thing to do is to copy
1814 &_src/EDITME_& to &_Local/Makefile_&, then read it and edit it appropriately.
1816 There are three settings that you must supply, because Exim will not build
1817 without them. They are the location of the run time configuration file
1818 (CONFIGURE_FILE), the directory in which Exim binaries will be installed
1819 (BIN_DIRECTORY), and the identity of the Exim user (EXIM_USER and
1820 maybe EXIM_GROUP as well). The value of CONFIGURE_FILE can in fact be
1821 a colon-separated list of file names; Exim uses the first of them that exists.
1823 There are a few other parameters that can be specified either at build time or
1824 at run time, to enable the same binary to be used on a number of different
1825 machines. However, if the locations of Exim's spool directory and log file
1826 directory (if not within the spool directory) are fixed, it is recommended that
1827 you specify them in &_Local/Makefile_& instead of at run time, so that errors
1828 detected early in Exim's execution (such as a malformed configuration file) can
1831 .cindex "content scanning" "specifying at build time"
1832 Exim's interfaces for calling virus and spam scanning software directly from
1833 access control lists are not compiled by default. If you want to include these
1834 facilities, you need to set
1836 WITH_CONTENT_SCAN=yes
1838 in your &_Local/Makefile_&. For details of the facilities themselves, see
1839 chapter &<<CHAPexiscan>>&.
1842 .cindex "&_Local/eximon.conf_&"
1843 .cindex "&_exim_monitor/EDITME_&"
1844 If you are going to build the Exim monitor, a similar configuration process is
1845 required. The file &_exim_monitor/EDITME_& must be edited appropriately for
1846 your installation and saved under the name &_Local/eximon.conf_&. If you are
1847 happy with the default settings described in &_exim_monitor/EDITME_&,
1848 &_Local/eximon.conf_& can be empty, but it must exist.
1850 This is all the configuration that is needed in straightforward cases for known
1851 operating systems. However, the building process is set up so that it is easy
1852 to override options that are set by default or by operating-system-specific
1853 configuration files, for example to change the name of the C compiler, which
1854 defaults to &%gcc%&. See section &<<SECToverride>>& below for details of how to
1859 .section "Support for iconv()" "SECID26"
1860 .cindex "&[iconv()]& support"
1862 The contents of header lines in messages may be encoded according to the rules
1863 described RFC 2047. This makes it possible to transmit characters that are not
1864 in the ASCII character set, and to label them as being in a particular
1865 character set. When Exim is inspecting header lines by means of the &%$h_%&
1866 mechanism, it decodes them, and translates them into a specified character set
1867 (default is set at build time). The translation is possible only if the operating system
1868 supports the &[iconv()]& function.
1870 However, some of the operating systems that supply &[iconv()]& do not support
1871 very many conversions. The GNU &%libiconv%& library (available from
1872 &url(http://www.gnu.org/software/libiconv/)) can be installed on such
1873 systems to remedy this deficiency, as well as on systems that do not supply
1874 &[iconv()]& at all. After installing &%libiconv%&, you should add
1878 to your &_Local/Makefile_& and rebuild Exim.
1882 .section "Including TLS/SSL encryption support" "SECTinctlsssl"
1883 .cindex "TLS" "including support for TLS"
1884 .cindex "encryption" "including support for"
1885 .cindex "SUPPORT_TLS"
1886 .cindex "OpenSSL" "building Exim with"
1887 .cindex "GnuTLS" "building Exim with"
1888 Exim can be built to support encrypted SMTP connections, using the STARTTLS
1889 command as per RFC 2487. It can also support legacy clients that expect to
1890 start a TLS session immediately on connection to a non-standard port (see the
1891 &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command
1894 If you want to build Exim with TLS support, you must first install either the
1895 OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for
1898 If OpenSSL is installed, you should set
1901 TLS_LIBS=-lssl -lcrypto
1903 in &_Local/Makefile_&. You may also need to specify the locations of the
1904 OpenSSL library and include files. For example:
1907 TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto
1908 TLS_INCLUDE=-I/usr/local/openssl/include/
1910 .cindex "pkg-config" "OpenSSL"
1911 If you have &'pkg-config'& available, then instead you can just use:
1914 USE_OPENSSL_PC=openssl
1916 .cindex "USE_GNUTLS"
1917 If GnuTLS is installed, you should set
1921 TLS_LIBS=-lgnutls -ltasn1 -lgcrypt
1923 in &_Local/Makefile_&, and again you may need to specify the locations of the
1924 library and include files. For example:
1928 TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt
1929 TLS_INCLUDE=-I/usr/gnu/include
1931 .cindex "pkg-config" "GnuTLS"
1932 If you have &'pkg-config'& available, then instead you can just use:
1936 USE_GNUTLS_PC=gnutls
1939 You do not need to set TLS_INCLUDE if the relevant directory is already
1940 specified in INCLUDE. Details of how to configure Exim to make use of TLS are
1941 given in chapter &<<CHAPTLS>>&.
1946 .section "Use of tcpwrappers" "SECID27"
1948 .cindex "tcpwrappers, building Exim to support"
1949 .cindex "USE_TCP_WRAPPERS"
1950 .cindex "TCP_WRAPPERS_DAEMON_NAME"
1951 .cindex "tcp_wrappers_daemon_name"
1952 Exim can be linked with the &'tcpwrappers'& library in order to check incoming
1953 SMTP calls using the &'tcpwrappers'& control files. This may be a convenient
1954 alternative to Exim's own checking facilities for installations that are
1955 already making use of &'tcpwrappers'& for other purposes. To do this, you
1956 should set USE_TCP_WRAPPERS in &_Local/Makefile_&, arrange for the file
1957 &_tcpd.h_& to be available at compile time, and also ensure that the library
1958 &_libwrap.a_& is available at link time, typically by including &%-lwrap%& in
1959 EXTRALIBS_EXIM. For example, if &'tcpwrappers'& is installed in &_/usr/local_&,
1962 USE_TCP_WRAPPERS=yes
1963 CFLAGS=-O -I/usr/local/include
1964 EXTRALIBS_EXIM=-L/usr/local/lib -lwrap
1966 in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control
1967 files is &"exim"&. For example, the line
1969 exim : LOCAL 192.168.1. .friendly.domain.example
1971 in your &_/etc/hosts.allow_& file allows connections from the local host, from
1972 the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&.
1973 All other connections are denied. The daemon name used by &'tcpwrappers'&
1974 can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in
1975 &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the
1976 configure file. Consult the &'tcpwrappers'& documentation for
1980 .section "Including support for IPv6" "SECID28"
1981 .cindex "IPv6" "including support for"
1982 Exim contains code for use on systems that have IPv6 support. Setting
1983 &`HAVE_IPV6=YES`& in &_Local/Makefile_& causes the IPv6 code to be included;
1984 it may also be necessary to set IPV6_INCLUDE and IPV6_LIBS on systems
1985 where the IPv6 support is not fully integrated into the normal include and
1988 Two different types of DNS record for handling IPv6 addresses have been
1989 defined. AAAA records (analogous to A records for IPv4) are in use, and are
1990 currently seen as the mainstream. Another record type called A6 was proposed
1991 as better than AAAA because it had more flexibility. However, it was felt to be
1992 over-complex, and its status was reduced to &"experimental"&.
1994 have a compile option for including A6 record support but this has now been
1999 .section "Dynamically loaded lookup module support" "SECTdynamicmodules"
2000 .cindex "lookup modules"
2001 .cindex "dynamic modules"
2002 .cindex ".so building"
2003 On some platforms, Exim supports not compiling all lookup types directly into
2004 the main binary, instead putting some into external modules which can be loaded
2006 This permits packagers to build Exim with support for lookups with extensive
2007 library dependencies without requiring all users to install all of those
2009 Most, but not all, lookup types can be built this way.
2011 Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be
2012 installed; Exim will only load modules from that directory, as a security
2013 measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined
2014 for your OS; see &_OS/Makefile-Linux_& for an example.
2015 Some other requirements for adjusting &`EXTRALIBS`& may also be necessary,
2016 see &_src/EDITME_& for details.
2018 Then, for each module to be loaded dynamically, define the relevant
2019 &`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes".
2020 For example, this will build in lsearch but load sqlite and mysql support
2029 .section "The building process" "SECID29"
2030 .cindex "build directory"
2031 Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been
2032 created, run &'make'& at the top level. It determines the architecture and
2033 operating system types, and creates a build directory if one does not exist.
2034 For example, on a Sun system running Solaris 8, the directory
2035 &_build-SunOS5-5.8-sparc_& is created.
2036 .cindex "symbolic link" "to source files"
2037 Symbolic links to relevant source files are installed in the build directory.
2039 If this is the first time &'make'& has been run, it calls a script that builds
2040 a make file inside the build directory, using the configuration files from the
2041 &_Local_& directory. The new make file is then passed to another instance of
2042 &'make'&. This does the real work, building a number of utility scripts, and
2043 then compiling and linking the binaries for the Exim monitor (if configured), a
2044 number of utility programs, and finally Exim itself. The command &`make
2045 makefile`& can be used to force a rebuild of the make file in the build
2046 directory, should this ever be necessary.
2048 If you have problems building Exim, check for any comments there may be in the
2049 &_README_& file concerning your operating system, and also take a look at the
2050 FAQ, where some common problems are covered.
2054 .section 'Output from &"make"&' "SECID283"
2055 The output produced by the &'make'& process for compile lines is often very
2056 unreadable, because these lines can be very long. For this reason, the normal
2057 output is suppressed by default, and instead output similar to that which
2058 appears when compiling the 2.6 Linux kernel is generated: just a short line for
2059 each module that is being compiled or linked. However, it is still possible to
2060 get the full output, by calling &'make'& like this:
2064 The value of FULLECHO defaults to &"@"&, the flag character that suppresses
2065 command reflection in &'make'&. When you ask for the full output, it is
2066 given in addition to the short output.
2070 .section "Overriding build-time options for Exim" "SECToverride"
2071 .cindex "build-time options, overriding"
2072 The main make file that is created at the beginning of the building process
2073 consists of the concatenation of a number of files which set configuration
2074 values, followed by a fixed set of &'make'& instructions. If a value is set
2075 more than once, the last setting overrides any previous ones. This provides a
2076 convenient way of overriding defaults. The files that are concatenated are, in
2079 &_OS/Makefile-Default_&
2080 &_OS/Makefile-_&<&'ostype'&>
2082 &_Local/Makefile-_&<&'ostype'&>
2083 &_Local/Makefile-_&<&'archtype'&>
2084 &_Local/Makefile-_&<&'ostype'&>-<&'archtype'&>
2085 &_OS/Makefile-Base_&
2087 .cindex "&_Local/Makefile_&"
2088 .cindex "building Exim" "operating system type"
2089 .cindex "building Exim" "architecture type"
2090 where <&'ostype'&> is the operating system type and <&'archtype'&> is the
2091 architecture type. &_Local/Makefile_& is required to exist, and the building
2092 process fails if it is absent. The other three &_Local_& files are optional,
2093 and are often not needed.
2095 The values used for <&'ostype'&> and <&'archtype'&> are obtained from scripts
2096 called &_scripts/os-type_& and &_scripts/arch-type_& respectively. If either of
2097 the environment variables EXIM_OSTYPE or EXIM_ARCHTYPE is set, their
2098 values are used, thereby providing a means of forcing particular settings.
2099 Otherwise, the scripts try to get values from the &%uname%& command. If this
2100 fails, the shell variables OSTYPE and ARCHTYPE are inspected. A number
2101 of &'ad hoc'& transformations are then applied, to produce the standard names
2102 that Exim expects. You can run these scripts directly from the shell in order
2103 to find out what values are being used on your system.
2106 &_OS/Makefile-Default_& contains comments about the variables that are set
2107 therein. Some (but not all) are mentioned below. If there is something that
2108 needs changing, review the contents of this file and the contents of the make
2109 file for your operating system (&_OS/Makefile-<ostype>_&) to see what the
2113 .cindex "building Exim" "overriding default settings"
2114 If you need to change any of the values that are set in &_OS/Makefile-Default_&
2115 or in &_OS/Makefile-<ostype>_&, or to add any new definitions, you do not
2116 need to change the original files. Instead, you should make the changes by
2117 putting the new values in an appropriate &_Local_& file. For example,
2118 .cindex "Tru64-Unix build-time settings"
2119 when building Exim in many releases of the Tru64-Unix (formerly Digital UNIX,
2120 formerly DEC-OSF1) operating system, it is necessary to specify that the C
2121 compiler is called &'cc'& rather than &'gcc'&. Also, the compiler must be
2122 called with the option &%-std1%&, to make it recognize some of the features of
2123 Standard C that Exim uses. (Most other compilers recognize Standard C by
2124 default.) To do this, you should create a file called &_Local/Makefile-OSF1_&
2125 containing the lines
2130 If you are compiling for just one operating system, it may be easier to put
2131 these lines directly into &_Local/Makefile_&.
2133 Keeping all your local configuration settings separate from the distributed
2134 files makes it easy to transfer them to new versions of Exim simply by copying
2135 the contents of the &_Local_& directory.
2138 .cindex "NIS lookup type" "including support for"
2139 .cindex "NIS+ lookup type" "including support for"
2140 .cindex "LDAP" "including support for"
2141 .cindex "lookup" "inclusion in binary"
2142 Exim contains support for doing LDAP, NIS, NIS+, and other kinds of file
2143 lookup, but not all systems have these components installed, so the default is
2144 not to include the relevant code in the binary. All the different kinds of file
2145 and database lookup that Exim supports are implemented as separate code modules
2146 which are included only if the relevant compile-time options are set. In the
2147 case of LDAP, NIS, and NIS+, the settings for &_Local/Makefile_& are:
2153 and similar settings apply to the other lookup types. They are all listed in
2154 &_src/EDITME_&. In many cases the relevant include files and interface
2155 libraries need to be installed before compiling Exim.
2156 .cindex "cdb" "including support for"
2157 However, there are some optional lookup types (such as cdb) for which
2158 the code is entirely contained within Exim, and no external include
2159 files or libraries are required. When a lookup type is not included in the
2160 binary, attempts to configure Exim to use it cause run time configuration
2163 .cindex "pkg-config" "lookups"
2164 .cindex "pkg-config" "authenticators"
2165 Many systems now use a tool called &'pkg-config'& to encapsulate information
2166 about how to compile against a library; Exim has some initial support for
2167 being able to use pkg-config for lookups and authenticators. For any given
2168 makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new
2169 variable with the &`_PC`& suffix in the name and assign as the value the
2170 name of the package to be queried. The results of querying via the
2171 &'pkg-config'& command will be added to the appropriate Makefile variables
2172 with &`+=`& directives, so your version of &'make'& will need to support that
2173 syntax. For instance:
2176 LOOKUP_SQLITE_PC=sqlite3
2178 AUTH_GSASL_PC=libgsasl
2179 AUTH_HEIMDAL_GSSAPI=yes
2180 AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi
2183 .cindex "Perl" "including support for"
2184 Exim can be linked with an embedded Perl interpreter, allowing Perl
2185 subroutines to be called during string expansion. To enable this facility,
2189 must be defined in &_Local/Makefile_&. Details of this facility are given in
2190 chapter &<<CHAPperl>>&.
2192 .cindex "X11 libraries, location of"
2193 The location of the X11 libraries is something that varies a lot between
2194 operating systems, and there may be different versions of X11 to cope
2195 with. Exim itself makes no use of X11, but if you are compiling the Exim
2196 monitor, the X11 libraries must be available.
2197 The following three variables are set in &_OS/Makefile-Default_&:
2200 XINCLUDE=-I$(X11)/include
2201 XLFLAGS=-L$(X11)/lib
2203 These are overridden in some of the operating-system configuration files. For
2204 example, in &_OS/Makefile-SunOS5_& there is
2207 XINCLUDE=-I$(X11)/include
2208 XLFLAGS=-L$(X11)/lib -R$(X11)/lib
2210 If you need to override the default setting for your operating system, place a
2211 definition of all three of these variables into your
2212 &_Local/Makefile-<ostype>_& file.
2215 If you need to add any extra libraries to the link steps, these can be put in a
2216 variable called EXTRALIBS, which appears in all the link commands, but by
2217 default is not defined. In contrast, EXTRALIBS_EXIM is used only on the
2218 command for linking the main Exim binary, and not for any associated utilities.
2220 .cindex "DBM libraries" "configuration for building"
2221 There is also DBMLIB, which appears in the link commands for binaries that
2222 use DBM functions (see also section &<<SECTdb>>&). Finally, there is
2223 EXTRALIBS_EXIMON, which appears only in the link step for the Exim monitor
2224 binary, and which can be used, for example, to include additional X11
2227 .cindex "configuration file" "editing"
2228 The make file copes with rebuilding Exim correctly if any of the configuration
2229 files are edited. However, if an optional configuration file is deleted, it is
2230 necessary to touch the associated non-optional file (that is,
2231 &_Local/Makefile_& or &_Local/eximon.conf_&) before rebuilding.
2234 .section "OS-specific header files" "SECID30"
2236 .cindex "building Exim" "OS-specific C header files"
2237 The &_OS_& directory contains a number of files with names of the form
2238 &_os.h-<ostype>_&. These are system-specific C header files that should not
2239 normally need to be changed. There is a list of macro settings that are
2240 recognized in the file &_OS/os.configuring_&, which should be consulted if you
2241 are porting Exim to a new operating system.
2245 .section "Overriding build-time options for the monitor" "SECID31"
2246 .cindex "building Eximon"
2247 A similar process is used for overriding things when building the Exim monitor,
2248 where the files that are involved are
2250 &_OS/eximon.conf-Default_&
2251 &_OS/eximon.conf-_&<&'ostype'&>
2252 &_Local/eximon.conf_&
2253 &_Local/eximon.conf-_&<&'ostype'&>
2254 &_Local/eximon.conf-_&<&'archtype'&>
2255 &_Local/eximon.conf-_&<&'ostype'&>-<&'archtype'&>
2257 .cindex "&_Local/eximon.conf_&"
2258 As with Exim itself, the final three files need not exist, and in this case the
2259 &_OS/eximon.conf-<ostype>_& file is also optional. The default values in
2260 &_OS/eximon.conf-Default_& can be overridden dynamically by setting environment
2261 variables of the same name, preceded by EXIMON_. For example, setting
2262 EXIMON_LOG_DEPTH in the environment overrides the value of
2263 LOG_DEPTH at run time.
2267 .section "Installing Exim binaries and scripts" "SECID32"
2268 .cindex "installing Exim"
2269 .cindex "BIN_DIRECTORY"
2270 The command &`make install`& runs the &(exim_install)& script with no
2271 arguments. The script copies binaries and utility scripts into the directory
2272 whose name is specified by the BIN_DIRECTORY setting in &_Local/Makefile_&.
2273 .cindex "setuid" "installing Exim with"
2274 The install script copies files only if they are newer than the files they are
2275 going to replace. The Exim binary is required to be owned by root and have the
2276 &'setuid'& bit set, for normal configurations. Therefore, you must run &`make
2277 install`& as root so that it can set up the Exim binary in this way. However, in
2278 some special situations (for example, if a host is doing no local deliveries)
2279 it may be possible to run Exim without making the binary setuid root (see
2280 chapter &<<CHAPsecurity>>& for details).
2282 .cindex "CONFIGURE_FILE"
2283 Exim's run time configuration file is named by the CONFIGURE_FILE setting
2284 in &_Local/Makefile_&. If this names a single file, and the file does not
2285 exist, the default configuration file &_src/configure.default_& is copied there
2286 by the installation script. If a run time configuration file already exists, it
2287 is left alone. If CONFIGURE_FILE is a colon-separated list, naming several
2288 alternative files, no default is installed.
2290 .cindex "system aliases file"
2291 .cindex "&_/etc/aliases_&"
2292 One change is made to the default configuration file when it is installed: the
2293 default configuration contains a router that references a system aliases file.
2294 The path to this file is set to the value specified by
2295 SYSTEM_ALIASES_FILE in &_Local/Makefile_& (&_/etc/aliases_& by default).
2296 If the system aliases file does not exist, the installation script creates it,
2297 and outputs a comment to the user.
2299 The created file contains no aliases, but it does contain comments about the
2300 aliases a site should normally have. Mail aliases have traditionally been
2301 kept in &_/etc/aliases_&. However, some operating systems are now using
2302 &_/etc/mail/aliases_&. You should check if yours is one of these, and change
2303 Exim's configuration if necessary.
2305 The default configuration uses the local host's name as the only local domain,
2306 and is set up to do local deliveries into the shared directory &_/var/mail_&,
2307 running as the local user. System aliases and &_.forward_& files in users' home
2308 directories are supported, but no NIS or NIS+ support is configured. Domains
2309 other than the name of the local host are routed using the DNS, with delivery
2312 It is possible to install Exim for special purposes (such as building a binary
2313 distribution) in a private part of the file system. You can do this by a
2316 make DESTDIR=/some/directory/ install
2318 This has the effect of pre-pending the specified directory to all the file
2319 paths, except the name of the system aliases file that appears in the default
2320 configuration. (If a default alias file is created, its name &'is'& modified.)
2321 For backwards compatibility, ROOT is used if DESTDIR is not set,
2322 but this usage is deprecated.
2324 .cindex "installing Exim" "what is not installed"
2325 Running &'make install'& does not copy the Exim 4 conversion script
2326 &'convert4r4'&. You will probably run this only once if you are
2327 upgrading from Exim 3. None of the documentation files in the &_doc_&
2328 directory are copied, except for the info files when you have set
2329 INFO_DIRECTORY, as described in section &<<SECTinsinfdoc>>& below.
2331 For the utility programs, old versions are renamed by adding the suffix &_.O_&
2332 to their names. The Exim binary itself, however, is handled differently. It is
2333 installed under a name that includes the version number and the compile number,
2334 for example &_exim-&version()-1_&. The script then arranges for a symbolic link
2335 called &_exim_& to point to the binary. If you are updating a previous version
2336 of Exim, the script takes care to ensure that the name &_exim_& is never absent
2337 from the directory (as seen by other processes).
2339 .cindex "installing Exim" "testing the script"
2340 If you want to see what the &'make install'& will do before running it for
2341 real, you can pass the &%-n%& option to the installation script by this
2344 make INSTALL_ARG=-n install
2346 The contents of the variable INSTALL_ARG are passed to the installation
2347 script. You do not need to be root to run this test. Alternatively, you can run
2348 the installation script directly, but this must be from within the build
2349 directory. For example, from the top-level Exim directory you could use this
2352 (cd build-SunOS5-5.5.1-sparc; ../scripts/exim_install -n)
2354 .cindex "installing Exim" "install script options"
2355 There are two other options that can be supplied to the installation script.
2358 &%-no_chown%& bypasses the call to change the owner of the installed binary
2359 to root, and the call to make it a setuid binary.
2361 &%-no_symlink%& bypasses the setting up of the symbolic link &_exim_& to the
2365 INSTALL_ARG can be used to pass these options to the script. For example:
2367 make INSTALL_ARG=-no_symlink install
2369 The installation script can also be given arguments specifying which files are
2370 to be copied. For example, to install just the Exim binary, and nothing else,
2371 without creating the symbolic link, you could use:
2373 make INSTALL_ARG='-no_symlink exim' install
2378 .section "Installing info documentation" "SECTinsinfdoc"
2379 .cindex "installing Exim" "&'info'& documentation"
2380 Not all systems use the GNU &'info'& system for documentation, and for this
2381 reason, the Texinfo source of Exim's documentation is not included in the main
2382 distribution. Instead it is available separately from the ftp site (see section
2385 If you have defined INFO_DIRECTORY in &_Local/Makefile_& and the Texinfo
2386 source of the documentation is found in the source tree, running &`make
2387 install`& automatically builds the info files and installs them.
2391 .section "Setting up the spool directory" "SECID33"
2392 .cindex "spool directory" "creating"
2393 When it starts up, Exim tries to create its spool directory if it does not
2394 exist. The Exim uid and gid are used for the owner and group of the spool
2395 directory. Sub-directories are automatically created in the spool directory as
2401 .section "Testing" "SECID34"
2402 .cindex "testing" "installation"
2403 Having installed Exim, you can check that the run time configuration file is
2404 syntactically valid by running the following command, which assumes that the
2405 Exim binary directory is within your PATH environment variable:
2409 If there are any errors in the configuration file, Exim outputs error messages.
2410 Otherwise it outputs the version number and build date,
2411 the DBM library that is being used, and information about which drivers and
2412 other optional code modules are included in the binary.
2413 Some simple routing tests can be done by using the address testing option. For
2416 &`exim -bt`& <&'local username'&>
2418 should verify that it recognizes a local mailbox, and
2420 &`exim -bt`& <&'remote address'&>
2422 a remote one. Then try getting it to deliver mail, both locally and remotely.
2423 This can be done by passing messages directly to Exim, without going through a
2424 user agent. For example:
2426 exim -v postmaster@your.domain.example
2427 From: user@your.domain.example
2428 To: postmaster@your.domain.example
2429 Subject: Testing Exim
2431 This is a test message.
2434 The &%-v%& option causes Exim to output some verification of what it is doing.
2435 In this case you should see copies of three log lines, one for the message's
2436 arrival, one for its delivery, and one containing &"Completed"&.
2438 .cindex "delivery" "problems with"
2439 If you encounter problems, look at Exim's log files (&'mainlog'& and
2440 &'paniclog'&) to see if there is any relevant information there. Another source
2441 of information is running Exim with debugging turned on, by specifying the
2442 &%-d%& option. If a message is stuck on Exim's spool, you can force a delivery
2443 with debugging turned on by a command of the form
2445 &`exim -d -M`& <&'exim-message-id'&>
2447 You must be root or an &"admin user"& in order to do this. The &%-d%& option
2448 produces rather a lot of output, but you can cut this down to specific areas.
2449 For example, if you use &%-d-all+route%& only the debugging information
2450 relevant to routing is included. (See the &%-d%& option in chapter
2451 &<<CHAPcommandline>>& for more details.)
2453 .cindex '&"sticky"& bit'
2454 .cindex "lock files"
2455 One specific problem that has shown up on some sites is the inability to do
2456 local deliveries into a shared mailbox directory, because it does not have the
2457 &"sticky bit"& set on it. By default, Exim tries to create a lock file before
2458 writing to a mailbox file, and if it cannot create the lock file, the delivery
2459 is deferred. You can get round this either by setting the &"sticky bit"& on the
2460 directory, or by setting a specific group for local deliveries and allowing
2461 that group to create files in the directory (see the comments above the
2462 &(local_delivery)& transport in the default configuration file). Another
2463 approach is to configure Exim not to use lock files, but just to rely on
2464 &[fcntl()]& locking instead. However, you should do this only if all user
2465 agents also use &[fcntl()]& locking. For further discussion of locking issues,
2466 see chapter &<<CHAPappendfile>>&.
2468 One thing that cannot be tested on a system that is already running an MTA is
2469 the receipt of incoming SMTP mail on the standard SMTP port. However, the
2470 &%-oX%& option can be used to run an Exim daemon that listens on some other
2471 port, or &'inetd'& can be used to do this. The &%-bh%& option and the
2472 &'exim_checkaccess'& utility can be used to check out policy controls on
2475 Testing a new version on a system that is already running Exim can most easily
2476 be done by building a binary with a different CONFIGURE_FILE setting. From
2477 within the run time configuration, all other file and directory names
2478 that Exim uses can be altered, in order to keep it entirely clear of the
2482 .section "Replacing another MTA with Exim" "SECID35"
2483 .cindex "replacing another MTA"
2484 Building and installing Exim for the first time does not of itself put it in
2485 general use. The name by which the system's MTA is called by mail user agents
2486 is either &_/usr/sbin/sendmail_&, or &_/usr/lib/sendmail_& (depending on the
2487 operating system), and it is necessary to make this name point to the &'exim'&
2488 binary in order to get the user agents to pass messages to Exim. This is
2489 normally done by renaming any existing file and making &_/usr/sbin/sendmail_&
2490 or &_/usr/lib/sendmail_&
2491 .cindex "symbolic link" "to &'exim'& binary"
2492 a symbolic link to the &'exim'& binary. It is a good idea to remove any setuid
2493 privilege and executable status from the old MTA. It is then necessary to stop
2494 and restart the mailer daemon, if one is running.
2496 .cindex "FreeBSD, MTA indirection"
2497 .cindex "&_/etc/mail/mailer.conf_&"
2498 Some operating systems have introduced alternative ways of switching MTAs. For
2499 example, if you are running FreeBSD, you need to edit the file
2500 &_/etc/mail/mailer.conf_& instead of setting up a symbolic link as just
2501 described. A typical example of the contents of this file for running Exim is
2504 sendmail /usr/exim/bin/exim
2505 send-mail /usr/exim/bin/exim
2506 mailq /usr/exim/bin/exim -bp
2507 newaliases /usr/bin/true
2509 Once you have set up the symbolic link, or edited &_/etc/mail/mailer.conf_&,
2510 your Exim installation is &"live"&. Check it by sending a message from your
2511 favourite user agent.
2513 You should consider what to tell your users about the change of MTA. Exim may
2514 have different capabilities to what was previously running, and there are
2515 various operational differences such as the text of messages produced by
2516 command line options and in bounce messages. If you allow your users to make
2517 use of Exim's filtering capabilities, you should make the document entitled
2518 &'Exim's interface to mail filtering'& available to them.
2522 .section "Upgrading Exim" "SECID36"
2523 .cindex "upgrading Exim"
2524 If you are already running Exim on your host, building and installing a new
2525 version automatically makes it available to MUAs, or any other programs that
2526 call the MTA directly. However, if you are running an Exim daemon, you do need
2527 to send it a HUP signal, to make it re-execute itself, and thereby pick up the
2528 new binary. You do not need to stop processing mail in order to install a new
2529 version of Exim. The install script does not modify an existing runtime
2535 .section "Stopping the Exim daemon on Solaris" "SECID37"
2536 .cindex "Solaris" "stopping Exim on"
2537 The standard command for stopping the mailer daemon on Solaris is
2539 /etc/init.d/sendmail stop
2541 If &_/usr/lib/sendmail_& has been turned into a symbolic link, this script
2542 fails to stop Exim because it uses the command &'ps -e'& and greps the output
2543 for the text &"sendmail"&; this is not present because the actual program name
2544 (that is, &"exim"&) is given by the &'ps'& command with these options. A
2545 solution is to replace the line that finds the process id with something like
2547 pid=`cat /var/spool/exim/exim-daemon.pid`
2549 to obtain the daemon's pid directly from the file that Exim saves it in.
2551 Note, however, that stopping the daemon does not &"stop Exim"&. Messages can
2552 still be received from local processes, and if automatic delivery is configured
2553 (the normal case), deliveries will still occur.
2558 . ////////////////////////////////////////////////////////////////////////////
2559 . ////////////////////////////////////////////////////////////////////////////
2561 .chapter "The Exim command line" "CHAPcommandline"
2562 .scindex IIDclo1 "command line" "options"
2563 .scindex IIDclo2 "options" "command line"
2564 Exim's command line takes the standard Unix form of a sequence of options,
2565 each starting with a hyphen character, followed by a number of arguments. The
2566 options are compatible with the main options of Sendmail, and there are also
2567 some additional options, some of which are compatible with Smail 3. Certain
2568 combinations of options do not make sense, and provoke an error if used.
2569 The form of the arguments depends on which options are set.
2572 .section "Setting options by program name" "SECID38"
2574 If Exim is called under the name &'mailq'&, it behaves as if the option &%-bp%&
2575 were present before any other options.
2576 The &%-bp%& option requests a listing of the contents of the mail queue on the
2578 This feature is for compatibility with some systems that contain a command of
2579 that name in one of the standard libraries, symbolically linked to
2580 &_/usr/sbin/sendmail_& or &_/usr/lib/sendmail_&.
2583 If Exim is called under the name &'rsmtp'& it behaves as if the option &%-bS%&
2584 were present before any other options, for compatibility with Smail. The
2585 &%-bS%& option is used for reading in a number of messages in batched SMTP
2589 If Exim is called under the name &'rmail'& it behaves as if the &%-i%& and
2590 &%-oee%& options were present before any other options, for compatibility with
2591 Smail. The name &'rmail'& is used as an interface by some UUCP systems.
2594 .cindex "queue runner"
2595 If Exim is called under the name &'runq'& it behaves as if the option &%-q%&
2596 were present before any other options, for compatibility with Smail. The &%-q%&
2597 option causes a single queue runner process to be started.
2599 .cindex "&'newaliases'&"
2600 .cindex "alias file" "building"
2601 .cindex "Sendmail compatibility" "calling Exim as &'newaliases'&"
2602 If Exim is called under the name &'newaliases'& it behaves as if the option
2603 &%-bi%& were present before any other options, for compatibility with Sendmail.
2604 This option is used for rebuilding Sendmail's alias file. Exim does not have
2605 the concept of a single alias file, but can be configured to run a given
2606 command if called with the &%-bi%& option.
2609 .section "Trusted and admin users" "SECTtrustedadmin"
2610 Some Exim options are available only to &'trusted users'& and others are
2611 available only to &'admin users'&. In the description below, the phrases &"Exim
2612 user"& and &"Exim group"& mean the user and group defined by EXIM_USER and
2613 EXIM_GROUP in &_Local/Makefile_& or set by the &%exim_user%& and
2614 &%exim_group%& options. These do not necessarily have to use the name &"exim"&.
2617 .cindex "trusted users" "definition of"
2618 .cindex "user" "trusted definition of"
2619 The trusted users are root, the Exim user, any user listed in the
2620 &%trusted_users%& configuration option, and any user whose current group or any
2621 supplementary group is one of those listed in the &%trusted_groups%&
2622 configuration option. Note that the Exim group is not automatically trusted.
2624 .cindex '&"From"& line'
2625 .cindex "envelope sender"
2626 Trusted users are always permitted to use the &%-f%& option or a leading
2627 &"From&~"& line to specify the envelope sender of a message that is passed to
2628 Exim through the local interface (see the &%-bm%& and &%-f%& options below).
2629 See the &%untrusted_set_sender%& option for a way of permitting non-trusted
2630 users to set envelope senders.
2632 .cindex "&'From:'& header line"
2633 .cindex "&'Sender:'& header line"
2634 .cindex "header lines" "From:"
2635 .cindex "header lines" "Sender:"
2636 For a trusted user, there is never any check on the contents of the &'From:'&
2637 header line, and a &'Sender:'& line is never added. Furthermore, any existing
2638 &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
2640 Trusted users may also specify a host name, host address, interface address,
2641 protocol name, ident value, and authentication data when submitting a message
2642 locally. Thus, they are able to insert messages into Exim's queue locally that
2643 have the characteristics of messages received from a remote host. Untrusted
2644 users may in some circumstances use &%-f%&, but can never set the other values
2645 that are available to trusted users.
2647 .cindex "user" "admin definition of"
2648 .cindex "admin user" "definition of"
2649 The admin users are root, the Exim user, and any user that is a member of the
2650 Exim group or of any group listed in the &%admin_groups%& configuration option.
2651 The current group does not have to be one of these groups.
2653 Admin users are permitted to list the queue, and to carry out certain
2654 operations on messages, for example, to force delivery failures. It is also
2655 necessary to be an admin user in order to see the full information provided by
2656 the Exim monitor, and full debugging output.
2658 By default, the use of the &%-M%&, &%-q%&, &%-R%&, and &%-S%& options to cause
2659 Exim to attempt delivery of messages on its queue is restricted to admin users.
2660 However, this restriction can be relaxed by setting the &%prod_requires_admin%&
2661 option false (that is, specifying &%no_prod_requires_admin%&).
2663 Similarly, the use of the &%-bp%& option to list all the messages in the queue
2664 is restricted to admin users unless &%queue_list_requires_admin%& is set
2669 &*Warning*&: If you configure your system so that admin users are able to
2670 edit Exim's configuration file, you are giving those users an easy way of
2671 getting root. There is further discussion of this issue at the start of chapter
2677 .section "Command line options" "SECID39"
2678 Exim's command line options are described in alphabetical order below. If none
2679 of the options that specifies a specific action (such as starting the daemon or
2680 a queue runner, or testing an address, or receiving a message in a specific
2681 format, or listing the queue) are present, and there is at least one argument
2682 on the command line, &%-bm%& (accept a local message on the standard input,
2683 with the arguments specifying the recipients) is assumed. Otherwise, Exim
2684 outputs a brief message about itself and exits.
2686 . ////////////////////////////////////////////////////////////////////////////
2687 . Insert a stylized XML comment here, to identify the start of the command line
2688 . options. This is for the benefit of the Perl script that automatically
2689 . creates a man page for the options.
2690 . ////////////////////////////////////////////////////////////////////////////
2693 <!-- === Start of command line options === -->
2700 .cindex "options" "command line; terminating"
2701 This is a pseudo-option whose only purpose is to terminate the options and
2702 therefore to cause subsequent command line items to be treated as arguments
2703 rather than options, even if they begin with hyphens.
2706 .oindex "&%--help%&"
2707 This option causes Exim to output a few sentences stating what it is.
2708 The same output is generated if the Exim binary is called with no options and
2711 .vitem &%--version%&
2712 .oindex "&%--version%&"
2713 This option is an alias for &%-bV%& and causes version information to be
2720 These options are used by Sendmail for selecting configuration files and are
2723 .vitem &%-B%&<&'type'&>
2725 .cindex "8-bit characters"
2726 .cindex "Sendmail compatibility" "8-bit characters"
2727 This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit
2728 clean; it ignores this option.
2733 .cindex "SMTP" "listener"
2734 .cindex "queue runner"
2735 This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually
2736 the &%-bd%& option is combined with the &%-q%&<&'time'&> option, to specify
2737 that the daemon should also initiate periodic queue runs.
2739 The &%-bd%& option can be used only by an admin user. If either of the &%-d%&
2740 (debugging) or &%-v%& (verifying) options are set, the daemon does not
2741 disconnect from the controlling terminal. When running this way, it can be
2742 stopped by pressing ctrl-C.
2744 By default, Exim listens for incoming connections to the standard SMTP port on
2745 all the host's running interfaces. However, it is possible to listen on other
2746 ports, on multiple ports, and only on specific interfaces. Chapter
2747 &<<CHAPinterfaces>>& contains a description of the options that control this.
2749 When a listening daemon
2750 .cindex "daemon" "process id (pid)"
2751 .cindex "pid (process id)" "of daemon"
2752 is started without the use of &%-oX%& (that is, without overriding the normal
2753 configuration), it writes its process id to a file called &_exim-daemon.pid_&
2754 in Exim's spool directory. This location can be overridden by setting
2755 PID_FILE_PATH in &_Local/Makefile_&. The file is written while Exim is still
2758 When &%-oX%& is used on the command line to start a listening daemon, the
2759 process id is not written to the normal pid file path. However, &%-oP%& can be
2760 used to specify a path on the command line if a pid file is required.
2764 .cindex "daemon" "restarting"
2765 can be used to cause the daemon to re-execute itself. This should be done
2766 whenever Exim's configuration file, or any file that is incorporated into it by
2767 means of the &%.include%& facility, is changed, and also whenever a new version
2768 of Exim is installed. It is not necessary to do this when other files that are
2769 referenced from the configuration (for example, alias files) are changed,
2770 because these are reread each time they are used.
2774 This option has the same effect as &%-bd%& except that it never disconnects
2775 from the controlling terminal, even when no debugging is specified.
2779 .cindex "testing" "string expansion"
2780 .cindex "expansion" "testing"
2781 Run Exim in expansion testing mode. Exim discards its root privilege, to
2782 prevent ordinary users from using this mode to read otherwise inaccessible
2783 files. If no arguments are given, Exim runs interactively, prompting for lines
2784 of data. Otherwise, it processes each argument in turn.
2786 If Exim was built with USE_READLINE=yes in &_Local/Makefile_&, it tries
2787 to load the &%libreadline%& library dynamically whenever the &%-be%& option is
2788 used without command line arguments. If successful, it uses the &[readline()]&
2789 function, which provides extensive line-editing facilities, for reading the
2790 test data. A line history is supported.
2792 Long expansion expressions can be split over several lines by using backslash
2793 continuations. As in Exim's run time configuration, white space at the start of
2794 continuation lines is ignored. Each argument or data line is passed through the
2795 string expansion mechanism, and the result is output. Variable values from the
2796 configuration file (for example, &$qualify_domain$&) are available, but no
2797 message-specific values (such as &$message_exim_id$&) are set, because no message
2798 is being processed (but see &%-bem%& and &%-Mset%&).
2800 &*Note*&: If you use this mechanism to test lookups, and you change the data
2801 files or databases you are using, you must exit and restart Exim before trying
2802 the same lookup again. Otherwise, because each Exim process caches the results
2803 of lookups, you will just get the same result as before.
2805 Macro processing is done on lines before string-expansion: new macros can be
2806 defined and macros will be expanded.
2807 Because macros in the config file are often used for secrets, those are only
2808 available to admin users.
2810 .vitem &%-bem%&&~<&'filename'&>
2812 .cindex "testing" "string expansion"
2813 .cindex "expansion" "testing"
2814 This option operates like &%-be%& except that it must be followed by the name
2815 of a file. For example:
2817 exim -bem /tmp/testmessage
2819 The file is read as a message (as if receiving a locally-submitted non-SMTP
2820 message) before any of the test expansions are done. Thus, message-specific
2821 variables such as &$message_size$& and &$header_from:$& are available. However,
2822 no &'Received:'& header is added to the message. If the &%-t%& option is set,
2823 recipients are read from the headers in the normal way, and are shown in the
2824 &$recipients$& variable. Note that recipients cannot be given on the command
2825 line, because further arguments are taken as strings to expand (just like
2828 .vitem &%-bF%&&~<&'filename'&>
2830 .cindex "system filter" "testing"
2831 .cindex "testing" "system filter"
2832 This option is the same as &%-bf%& except that it assumes that the filter being
2833 tested is a system filter. The additional commands that are available only in
2834 system filters are recognized.
2836 .vitem &%-bf%&&~<&'filename'&>
2838 .cindex "filter" "testing"
2839 .cindex "testing" "filter file"
2840 .cindex "forward file" "testing"
2841 .cindex "testing" "forward file"
2842 .cindex "Sieve filter" "testing"
2843 This option runs Exim in user filter testing mode; the file is the filter file
2844 to be tested, and a test message must be supplied on the standard input. If
2845 there are no message-dependent tests in the filter, an empty file can be
2848 If you want to test a system filter file, use &%-bF%& instead of &%-bf%&. You
2849 can use both &%-bF%& and &%-bf%& on the same command, in order to test a system
2850 filter and a user filter in the same run. For example:
2852 exim -bF /system/filter -bf /user/filter </test/message
2854 This is helpful when the system filter adds header lines or sets filter
2855 variables that are used by the user filter.
2857 If the test filter file does not begin with one of the special lines
2862 it is taken to be a normal &_.forward_& file, and is tested for validity under
2863 that interpretation. See sections &<<SECTitenonfilred>>& to
2864 &<<SECTspecitredli>>& for a description of the possible contents of non-filter
2867 The result of an Exim command that uses &%-bf%&, provided no errors are
2868 detected, is a list of the actions that Exim would try to take if presented
2869 with the message for real. More details of filter testing are given in the
2870 separate document entitled &'Exim's interfaces to mail filtering'&.
2872 When testing a filter file,
2873 .cindex "&""From""& line"
2874 .cindex "envelope sender"
2875 .oindex "&%-f%&" "for filter testing"
2876 the envelope sender can be set by the &%-f%& option,
2877 or by a &"From&~"& line at the start of the test message. Various parameters
2878 that would normally be taken from the envelope recipient address of the message
2879 can be set by means of additional command line options (see the next four
2882 .vitem &%-bfd%&&~<&'domain'&>
2884 .vindex "&$qualify_domain$&"
2885 This sets the domain of the recipient address when a filter file is being
2886 tested by means of the &%-bf%& option. The default is the value of
2889 .vitem &%-bfl%&&~<&'local&~part'&>
2891 This sets the local part of the recipient address when a filter file is being
2892 tested by means of the &%-bf%& option. The default is the username of the
2893 process that calls Exim. A local part should be specified with any prefix or
2894 suffix stripped, because that is how it appears to the filter when a message is
2895 actually being delivered.
2897 .vitem &%-bfp%&&~<&'prefix'&>
2899 This sets the prefix of the local part of the recipient address when a filter
2900 file is being tested by means of the &%-bf%& option. The default is an empty
2903 .vitem &%-bfs%&&~<&'suffix'&>
2905 This sets the suffix of the local part of the recipient address when a filter
2906 file is being tested by means of the &%-bf%& option. The default is an empty
2909 .vitem &%-bh%&&~<&'IP&~address'&>
2911 .cindex "testing" "incoming SMTP"
2912 .cindex "SMTP" "testing incoming"
2913 .cindex "testing" "relay control"
2914 .cindex "relaying" "testing configuration"
2915 .cindex "policy control" "testing"
2916 .cindex "debugging" "&%-bh%& option"
2917 This option runs a fake SMTP session as if from the given IP address, using the
2918 standard input and output. The IP address may include a port number at the end,
2919 after a full stop. For example:
2921 exim -bh 10.9.8.7.1234
2922 exim -bh fe80::a00:20ff:fe86:a061.5678
2924 When an IPv6 address is given, it is converted into canonical form. In the case
2925 of the second example above, the value of &$sender_host_address$& after
2926 conversion to the canonical form is
2927 &`fe80:0000:0000:0a00:20ff:fe86:a061.5678`&.
2929 Comments as to what is going on are written to the standard error file. These
2930 include lines beginning with &"LOG"& for anything that would have been logged.
2931 This facility is provided for testing configuration options for incoming
2932 messages, to make sure they implement the required policy. For example, you can
2933 test your relay controls using &%-bh%&.
2937 You can test features of the configuration that rely on ident (RFC 1413)
2938 information by using the &%-oMt%& option. However, Exim cannot actually perform
2939 an ident callout when testing using &%-bh%& because there is no incoming SMTP
2942 &*Warning 2*&: Address verification callouts (see section &<<SECTcallver>>&)
2943 are also skipped when testing using &%-bh%&. If you want these callouts to
2944 occur, use &%-bhc%& instead.
2946 Messages supplied during the testing session are discarded, and nothing is
2947 written to any of the real log files. There may be pauses when DNS (and other)
2948 lookups are taking place, and of course these may time out. The &%-oMi%& option
2949 can be used to specify a specific IP interface and port if this is important,
2950 and &%-oMaa%& and &%-oMai%& can be used to set parameters as if the SMTP
2951 session were authenticated.
2953 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose
2954 output just states whether a given recipient address from a given host is
2955 acceptable or not. See section &<<SECTcheckaccess>>&.
2957 Features such as authentication and encryption, where the client input is not
2958 plain text, cannot easily be tested with &%-bh%&. Instead, you should use a
2959 specialized SMTP test program such as
2960 &url(http://jetmore.org/john/code/#swaks,swaks).
2962 .vitem &%-bhc%&&~<&'IP&~address'&>
2964 This option operates in the same way as &%-bh%&, except that address
2965 verification callouts are performed if required. This includes consulting and
2966 updating the callout cache database.
2970 .cindex "alias file" "building"
2971 .cindex "building alias file"
2972 .cindex "Sendmail compatibility" "&%-bi%& option"
2973 Sendmail interprets the &%-bi%& option as a request to rebuild its alias file.
2974 Exim does not have the concept of a single alias file, and so it cannot mimic
2975 this behaviour. However, calls to &_/usr/lib/sendmail_& with the &%-bi%& option
2976 tend to appear in various scripts such as NIS make files, so the option must be
2979 If &%-bi%& is encountered, the command specified by the &%bi_command%&
2980 configuration option is run, under the uid and gid of the caller of Exim. If
2981 the &%-oA%& option is used, its value is passed to the command as an argument.
2982 The command set by &%bi_command%& may not contain arguments. The command can
2983 use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files
2984 if this is required. If the &%bi_command%& option is not set, calling Exim with
2987 . // Keep :help first, then the rest in alphabetical order
2989 .oindex "&%-bI:help%&"
2990 .cindex "querying exim information"
2991 We shall provide various options starting &`-bI:`& for querying Exim for
2992 information. The output of many of these will be intended for machine
2993 consumption. This one is not. The &%-bI:help%& option asks Exim for a
2994 synopsis of supported options beginning &`-bI:`&. Use of any of these
2995 options shall cause Exim to exit after producing the requested output.
2998 .oindex "&%-bI:dscp%&"
2999 .cindex "DSCP" "values"
3000 This option causes Exim to emit an alphabetically sorted list of all
3001 recognised DSCP names.
3003 .vitem &%-bI:sieve%&
3004 .oindex "&%-bI:sieve%&"
3005 .cindex "Sieve filter" "capabilities"
3006 This option causes Exim to emit an alphabetically sorted list of all supported
3007 Sieve protocol extensions on stdout, one per line. This is anticipated to be
3008 useful for ManageSieve (RFC 5804) implementations, in providing that protocol's
3009 &`SIEVE`& capability response line. As the precise list may depend upon
3010 compile-time build options, which this option will adapt to, this is the only
3011 way to guarantee a correct response.
3015 .cindex "local message reception"
3016 This option runs an Exim receiving process that accepts an incoming,
3017 locally-generated message on the standard input. The recipients are given as the
3018 command arguments (except when &%-t%& is also present &-- see below). Each
3019 argument can be a comma-separated list of RFC 2822 addresses. This is the
3020 default option for selecting the overall action of an Exim call; it is assumed
3021 if no other conflicting option is present.
3023 If any addresses in the message are unqualified (have no domain), they are
3024 qualified by the values of the &%qualify_domain%& or &%qualify_recipient%&
3025 options, as appropriate. The &%-bnq%& option (see below) provides a way of
3026 suppressing this for special cases.
3028 Policy checks on the contents of local messages can be enforced by means of
3029 the non-SMTP ACL. See chapter &<<CHAPACL>>& for details.
3031 .cindex "return code" "for &%-bm%&"
3032 The return code is zero if the message is successfully accepted. Otherwise, the
3033 action is controlled by the &%-oe%&&'x'& option setting &-- see below.
3036 .cindex "message" "format"
3037 .cindex "format" "message"
3038 .cindex "&""From""& line"
3039 .cindex "UUCP" "&""From""& line"
3040 .cindex "Sendmail compatibility" "&""From""& line"
3041 of the message must be as defined in RFC 2822, except that, for
3042 compatibility with Sendmail and Smail, a line in one of the forms
3044 From sender Fri Jan 5 12:55 GMT 1997
3045 From sender Fri, 5 Jan 97 12:55:01
3047 (with the weekday optional, and possibly with additional text after the date)
3048 is permitted to appear at the start of the message. There appears to be no
3049 authoritative specification of the format of this line. Exim recognizes it by
3050 matching against the regular expression defined by the &%uucp_from_pattern%&
3051 option, which can be changed if necessary.
3053 .oindex "&%-f%&" "overriding &""From""& line"
3054 The specified sender is treated as if it were given as the argument to the
3055 &%-f%& option, but if a &%-f%& option is also present, its argument is used in
3056 preference to the address taken from the message. The caller of Exim must be a
3057 trusted user for the sender of a message to be set in this way.
3059 .vitem &%-bmalware%&&~<&'filename'&>
3060 .oindex "&%-bmalware%&"
3061 .cindex "testing", "malware"
3062 .cindex "malware scan test"
3063 This debugging option causes Exim to scan the given file or directory
3064 (depending on the used scanner interface),
3065 using the malware scanning framework. The option of &%av_scanner%& influences
3066 this option, so if &%av_scanner%&'s value is dependent upon an expansion then
3067 the expansion should have defaults which apply to this invocation. ACLs are
3068 not invoked, so if &%av_scanner%& references an ACL variable then that variable
3069 will never be populated and &%-bmalware%& will fail.
3071 Exim will have changed working directory before resolving the filename, so
3072 using fully qualified pathnames is advisable. Exim will be running as the Exim
3073 user when it tries to open the file, rather than as the invoking user.
3074 This option requires admin privileges.
3076 The &%-bmalware%& option will not be extended to be more generally useful,
3077 there are better tools for file-scanning. This option exists to help
3078 administrators verify their Exim and AV scanner configuration.
3082 .cindex "address qualification, suppressing"
3083 By default, Exim automatically qualifies unqualified addresses (those
3084 without domains) that appear in messages that are submitted locally (that
3085 is, not over TCP/IP). This qualification applies both to addresses in
3086 envelopes, and addresses in header lines. Sender addresses are qualified using
3087 &%qualify_domain%&, and recipient addresses using &%qualify_recipient%& (which
3088 defaults to the value of &%qualify_domain%&).
3090 Sometimes, qualification is not wanted. For example, if &%-bS%& (batch SMTP) is
3091 being used to re-submit messages that originally came from remote hosts after
3092 content scanning, you probably do not want to qualify unqualified addresses in
3093 header lines. (Such lines will be present only if you have not enabled a header
3094 syntax check in the appropriate ACL.)
3096 The &%-bnq%& option suppresses all qualification of unqualified addresses in
3097 messages that originate on the local host. When this is used, unqualified
3098 addresses in the envelope provoke errors (causing message rejection) and
3099 unqualified addresses in header lines are left alone.
3104 .cindex "configuration options" "extracting"
3105 .cindex "options" "configuration &-- extracting"
3106 If this option is given with no arguments, it causes the values of all Exim's
3107 main configuration options to be written to the standard output. The values
3108 of one or more specific options can be requested by giving their names as
3109 arguments, for example:
3111 exim -bP qualify_domain hold_domains
3113 .cindex "hiding configuration option values"
3114 .cindex "configuration options" "hiding value of"
3115 .cindex "options" "hiding value of"
3116 However, any option setting that is preceded by the word &"hide"& in the
3117 configuration file is not shown in full, except to an admin user. For other
3118 users, the output is as in this example:
3120 mysql_servers = <value not displayable>
3122 If &%config%& is given as an argument, the config is
3123 output, as it was parsed, any include file resolved, any comment removed.
3125 If &%config_file%& is given as an argument, the name of the run time
3126 configuration file is output. (&%configure_file%& works too, for
3127 backward compatibility.)
3128 If a list of configuration files was supplied, the value that is output here
3129 is the name of the file that was actually used.
3131 .cindex "options" "hiding name of"
3132 If the &%-n%& flag is given, then for most modes of &%-bP%& operation the
3133 name will not be output.
3135 .cindex "daemon" "process id (pid)"
3136 .cindex "pid (process id)" "of daemon"
3137 If &%log_file_path%& or &%pid_file_path%& are given, the names of the
3138 directories where log files and daemon pid files are written are output,
3139 respectively. If these values are unset, log files are written in a
3140 sub-directory of the spool directory called &%log%&, and the pid file is
3141 written directly into the spool directory.
3143 If &%-bP%& is followed by a name preceded by &`+`&, for example,
3145 exim -bP +local_domains
3147 it searches for a matching named list of any type (domain, host, address, or
3148 local part) and outputs what it finds.
3150 .cindex "options" "router &-- extracting"
3151 .cindex "options" "transport &-- extracting"
3152 .cindex "options" "authenticator &-- extracting"
3153 If one of the words &%router%&, &%transport%&, or &%authenticator%& is given,
3154 followed by the name of an appropriate driver instance, the option settings for
3155 that driver are output. For example:
3157 exim -bP transport local_delivery
3159 The generic driver options are output first, followed by the driver's private
3160 options. A list of the names of drivers of a particular type can be obtained by
3161 using one of the words &%router_list%&, &%transport_list%&, or
3162 &%authenticator_list%&, and a complete list of all drivers with their option
3163 settings can be obtained by using &%routers%&, &%transports%&, or
3166 .cindex "environment"
3167 If &%environment%& is given as an argument, the set of environment
3168 variables is output, line by line. Using the &%-n%& flag suppresses the value of the
3171 .cindex "options" "macro &-- extracting"
3172 If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%&
3173 are available, similarly to the drivers. Because macros are sometimes used
3174 for storing passwords, this option is restricted.
3175 The output format is one item per line.
3176 For the "-bP macro <name>" form, if no such macro is found
3177 the exit status will be nonzero.
3181 .cindex "queue" "listing messages on"
3182 .cindex "listing" "messages on the queue"
3183 This option requests a listing of the contents of the mail queue on the
3184 standard output. If the &%-bp%& option is followed by a list of message ids,
3185 just those messages are listed. By default, this option can be used only by an
3186 admin user. However, the &%queue_list_requires_admin%& option can be set false
3187 to allow any user to see the queue.
3189 Each message on the queue is displayed as in the following example:
3191 25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
3192 red.king@looking-glass.fict.example
3195 .cindex "message" "size in queue listing"
3196 .cindex "size" "of message"
3197 The first line contains the length of time the message has been on the queue
3198 (in this case 25 minutes), the size of the message (2.9K), the unique local
3199 identifier for the message, and the message sender, as contained in the
3200 envelope. For bounce messages, the sender address is empty, and appears as
3201 &"<>"&. If the message was submitted locally by an untrusted user who overrode
3202 the default sender address, the user's login name is shown in parentheses
3203 before the sender address.
3205 .cindex "frozen messages" "in queue listing"
3206 If the message is frozen (attempts to deliver it are suspended) then the text
3207 &"*** frozen ***"& is displayed at the end of this line.
3209 The recipients of the message (taken from the envelope, not the headers) are
3210 displayed on subsequent lines. Those addresses to which the message has already
3211 been delivered are marked with the letter D. If an original address gets
3212 expanded into several addresses via an alias or forward file, the original is
3213 displayed with a D only when deliveries for all of its child addresses are
3219 This option operates like &%-bp%&, but in addition it shows delivered addresses
3220 that were generated from the original top level address(es) in each message by
3221 alias or forwarding operations. These addresses are flagged with &"+D"& instead
3227 .cindex "queue" "count of messages on"
3228 This option counts the number of messages on the queue, and writes the total
3229 to the standard output. It is restricted to admin users, unless
3230 &%queue_list_requires_admin%& is set false.
3235 This option operates like &%-bp%&, but the output is not sorted into
3236 chronological order of message arrival. This can speed it up when there are
3237 lots of messages on the queue, and is particularly useful if the output is
3238 going to be post-processed in a way that doesn't need the sorting.
3242 This option is a combination of &%-bpr%& and &%-bpa%&.
3246 This option is a combination of &%-bpr%& and &%-bpu%&.
3251 This option operates like &%-bp%& but shows only undelivered top-level
3252 addresses for each message displayed. Addresses generated by aliasing or
3253 forwarding are not shown, unless the message was deferred after processing by a
3254 router with the &%one_time%& option set.
3259 .cindex "testing" "retry configuration"
3260 .cindex "retry" "configuration testing"
3261 This option is for testing retry rules, and it must be followed by up to three
3262 arguments. It causes Exim to look for a retry rule that matches the values
3263 and to write it to the standard output. For example:
3265 exim -brt bach.comp.mus.example
3266 Retry rule: *.comp.mus.example F,2h,15m; F,4d,30m;
3268 See chapter &<<CHAPretry>>& for a description of Exim's retry rules. The first
3269 argument, which is required, can be a complete address in the form
3270 &'local_part@domain'&, or it can be just a domain name. If the second argument
3271 contains a dot, it is interpreted as an optional second domain name; if no
3272 retry rule is found for the first argument, the second is tried. This ties in
3273 with Exim's behaviour when looking for retry rules for remote hosts &-- if no
3274 rule is found that matches the host, one that matches the mail domain is
3275 sought. Finally, an argument that is the name of a specific delivery error, as
3276 used in setting up retry rules, can be given. For example:
3278 exim -brt haydn.comp.mus.example quota_3d
3279 Retry rule: *@haydn.comp.mus.example quota_3d F,1h,15m
3284 .cindex "testing" "rewriting"
3285 .cindex "rewriting" "testing"
3286 This option is for testing address rewriting rules, and it must be followed by
3287 a single argument, consisting of either a local part without a domain, or a
3288 complete address with a fully qualified domain. Exim outputs how this address
3289 would be rewritten for each possible place it might appear. See chapter
3290 &<<CHAPrewrite>>& for further details.
3294 .cindex "SMTP" "batched incoming"
3295 .cindex "batched SMTP input"
3296 This option is used for batched SMTP input, which is an alternative interface
3297 for non-interactive local message submission. A number of messages can be
3298 submitted in a single run. However, despite its name, this is not really SMTP
3299 input. Exim reads each message's envelope from SMTP commands on the standard
3300 input, but generates no responses. If the caller is trusted, or
3301 &%untrusted_set_sender%& is set, the senders in the SMTP MAIL commands are
3302 believed; otherwise the sender is always the caller of Exim.
3304 The message itself is read from the standard input, in SMTP format (leading
3305 dots doubled), terminated by a line containing just a single dot. An error is
3306 provoked if the terminating dot is missing. A further message may then follow.
3308 As for other local message submissions, the contents of incoming batch SMTP
3309 messages can be checked using the non-SMTP ACL (see chapter &<<CHAPACL>>&).
3310 Unqualified addresses are automatically qualified using &%qualify_domain%& and
3311 &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used.
3313 Some other SMTP commands are recognized in the input. HELO and EHLO act
3314 as RSET; VRFY, EXPN, ETRN, and HELP act as NOOP;
3315 QUIT quits, ignoring the rest of the standard input.
3317 .cindex "return code" "for &%-bS%&"
3318 If any error is encountered, reports are written to the standard output and
3319 error streams, and Exim gives up immediately. The return code is 0 if no error
3320 was detected; it is 1 if one or more messages were accepted before the error
3321 was detected; otherwise it is 2.
3323 More details of input using batched SMTP are given in section
3324 &<<SECTincomingbatchedSMTP>>&.
3328 .cindex "SMTP" "local input"
3329 .cindex "local SMTP input"
3330 This option causes Exim to accept one or more messages by reading SMTP commands
3331 on the standard input, and producing SMTP replies on the standard output. SMTP
3332 policy controls, as defined in ACLs (see chapter &<<CHAPACL>>&) are applied.
3333 Some user agents use this interface as a way of passing locally-generated
3334 messages to the MTA.
3337 .cindex "sender" "source of"
3338 this usage, if the caller of Exim is trusted, or &%untrusted_set_sender%& is
3339 set, the senders of messages are taken from the SMTP MAIL commands.
3340 Otherwise the content of these commands is ignored and the sender is set up as
3341 the calling user. Unqualified addresses are automatically qualified using
3342 &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the
3343 &%-bnq%& option is used.
3347 &%-bs%& option is also used to run Exim from &'inetd'&, as an alternative to
3348 using a listening daemon. Exim can distinguish the two cases by checking
3349 whether the standard input is a TCP/IP socket. When Exim is called from
3350 &'inetd'&, the source of the mail is assumed to be remote, and the comments
3351 above concerning senders and qualification do not apply. In this situation,
3352 Exim behaves in exactly the same way as it does when receiving a message via
3353 the listening daemon.
3357 .cindex "testing" "addresses"
3358 .cindex "address" "testing"
3359 This option runs Exim in address testing mode, in which each argument is taken
3360 as a recipient address to be tested for deliverability. The results are
3361 written to the standard output. If a test fails, and the caller is not an admin
3362 user, no details of the failure are output, because these might contain
3363 sensitive information such as usernames and passwords for database lookups.
3365 If no arguments are given, Exim runs in an interactive manner, prompting with a
3366 right angle bracket for addresses to be tested.
3368 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3369 &[readline()]& function, because it is running as &'root'& and there are
3372 Each address is handled as if it were the recipient address of a message
3373 (compare the &%-bv%& option). It is passed to the routers and the result is
3374 written to the standard output. However, any router that has
3375 &%no_address_test%& set is bypassed. This can make &%-bt%& easier to use for
3376 genuine routing tests if your first router passes everything to a scanner
3379 .cindex "return code" "for &%-bt%&"
3380 The return code is 2 if any address failed outright; it is 1 if no address
3381 failed outright but at least one could not be resolved for some reason. Return
3382 code 0 is given only when all addresses succeed.
3384 .cindex "duplicate addresses"
3385 &*Note*&: When actually delivering a message, Exim removes duplicate recipient
3386 addresses after routing is complete, so that only one delivery takes place.
3387 This does not happen when testing with &%-bt%&; the full results of routing are
3390 &*Warning*&: &%-bt%& can only do relatively simple testing. If any of the
3391 routers in the configuration makes any tests on the sender address of a
3393 .oindex "&%-f%&" "for address testing"
3394 you can use the &%-f%& option to set an appropriate sender when running
3395 &%-bt%& tests. Without it, the sender is assumed to be the calling user at the
3396 default qualifying domain. However, if you have set up (for example) routers
3397 whose behaviour depends on the contents of an incoming message, you cannot test
3398 those conditions using &%-bt%&. The &%-N%& option provides a possible way of
3403 .cindex "version number of Exim"
3404 This option causes Exim to write the current version number, compilation
3405 number, and compilation date of the &'exim'& binary to the standard output.
3406 It also lists the DBM library that is being used, the optional modules (such as
3407 specific lookup types), the drivers that are included in the binary, and the
3408 name of the run time configuration file that is in use.
3410 As part of its operation, &%-bV%& causes Exim to read and syntax check its
3411 configuration file. However, this is a static check only. It cannot check
3412 values that are to be expanded. For example, although a misspelt ACL verb is
3413 detected, an error in the verb's arguments is not. You cannot rely on &%-bV%&
3414 alone to discover (for example) all the typos in the configuration; some
3415 realistic testing is needed. The &%-bh%& and &%-N%& options provide more
3416 dynamic testing facilities.
3420 .cindex "verifying address" "using &%-bv%&"
3421 .cindex "address" "verification"
3422 This option runs Exim in address verification mode, in which each argument is
3423 taken as a recipient address to be verified by the routers. (This does
3424 not involve any verification callouts). During normal operation, verification
3425 happens mostly as a consequence processing a &%verify%& condition in an ACL
3426 (see chapter &<<CHAPACL>>&). If you want to test an entire ACL, possibly
3427 including callouts, see the &%-bh%& and &%-bhc%& options.
3429 If verification fails, and the caller is not an admin user, no details of the
3430 failure are output, because these might contain sensitive information such as
3431 usernames and passwords for database lookups.
3433 If no arguments are given, Exim runs in an interactive manner, prompting with a
3434 right angle bracket for addresses to be verified.
3436 Unlike the &%-be%& test option, you cannot arrange for Exim to use the
3437 &[readline()]& function, because it is running as &'exim'& and there are
3440 Verification differs from address testing (the &%-bt%& option) in that routers
3441 that have &%no_verify%& set are skipped, and if the address is accepted by a
3442 router that has &%fail_verify%& set, verification fails. The address is
3443 verified as a recipient if &%-bv%& is used; to test verification for a sender
3444 address, &%-bvs%& should be used.
3446 If the &%-v%& option is not set, the output consists of a single line for each
3447 address, stating whether it was verified or not, and giving a reason in the
3448 latter case. Without &%-v%&, generating more than one address by redirection
3449 causes verification to end successfully, without considering the generated
3450 addresses. However, if just one address is generated, processing continues,
3451 and the generated address must verify successfully for the overall verification
3454 When &%-v%& is set, more details are given of how the address has been handled,
3455 and in the case of address redirection, all the generated addresses are also
3456 considered. Verification may succeed for some and fail for others.
3459 .cindex "return code" "for &%-bv%&"
3460 return code is 2 if any address failed outright; it is 1 if no address
3461 failed outright but at least one could not be resolved for some reason. Return
3462 code 0 is given only when all addresses succeed.
3464 If any of the routers in the configuration makes any tests on the sender
3465 address of a message, you should use the &%-f%& option to set an appropriate
3466 sender when running &%-bv%& tests. Without it, the sender is assumed to be the
3467 calling user at the default qualifying domain.
3471 This option acts like &%-bv%&, but verifies the address as a sender rather
3472 than a recipient address. This affects any rewriting and qualification that
3479 .cindex "inetd" "wait mode"
3480 This option runs Exim as a daemon, awaiting incoming SMTP connections,
3481 similarly to the &%-bd%& option. All port specifications on the command-line
3482 and in the configuration file are ignored. Queue-running may not be specified.
3484 In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is
3485 listening for connections. This permits the system to start up and have
3486 inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for
3487 each port only when the first connection is received.
3489 If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after
3490 which the daemon will exit, which should cause inetd to listen once more.
3492 .vitem &%-C%&&~<&'filelist'&>
3494 .cindex "configuration file" "alternate"
3495 .cindex "CONFIGURE_FILE"
3496 .cindex "alternate configuration file"
3497 This option causes Exim to find the run time configuration file from the given
3498 list instead of from the list specified by the CONFIGURE_FILE
3499 compile-time setting. Usually, the list will consist of just a single file
3500 name, but it can be a colon-separated list of names. In this case, the first
3501 file that exists is used. Failure to open an existing file stops Exim from
3502 proceeding any further along the list, and an error is generated.
3504 When this option is used by a caller other than root, and the list is different
3505 from the compiled-in list, Exim gives up its root privilege immediately, and
3506 runs with the real and effective uid and gid set to those of the caller.
3507 However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that
3508 file contains a list of full pathnames, one per line, for configuration files
3509 which are trusted. Root privilege is retained for any configuration file so
3510 listed, as long as the caller is the Exim user (or the user specified in the
3511 CONFIGURE_OWNER option, if any), and as long as the configuration file is
3512 not writeable by inappropriate users or groups.
3514 Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a
3515 configuration using &%-C%& right through message reception and delivery,
3516 even if the caller is root. The reception works, but by that time, Exim is
3517 running as the Exim user, so when it re-executes to regain privilege for the
3518 delivery, the use of &%-C%& causes privilege to be lost. However, root can
3519 test reception and delivery using two separate commands (one to put a message
3520 on the queue, using &%-odq%&, and another to do the delivery, using &%-M%&).
3522 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
3523 prefix string with which any file named in a &%-C%& command line option
3524 must start. In addition, the file name must not contain the sequence &`/../`&.
3525 However, if the value of the &%-C%& option is identical to the value of
3526 CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as
3527 usual. There is no default setting for ALT_CONFIG_PREFIX; when it is
3528 unset, any file name can be used with &%-C%&.
3530 ALT_CONFIG_PREFIX can be used to confine alternative configuration files
3531 to a directory to which only root has access. This prevents someone who has
3532 broken into the Exim account from running a privileged Exim with an arbitrary
3535 The &%-C%& facility is useful for ensuring that configuration files are
3536 syntactically correct, but cannot be used for test deliveries, unless the
3537 caller is privileged, or unless it is an exotic configuration that does not
3538 require privilege. No check is made on the owner or group of the files
3539 specified by this option.
3542 .vitem &%-D%&<&'macro'&>=<&'value'&>
3544 .cindex "macro" "setting on command line"
3545 This option can be used to override macro definitions in the configuration file
3546 (see section &<<SECTmacrodefs>>&). However, like &%-C%&, if it is used by an
3547 unprivileged caller, it causes Exim to give up its root privilege.
3548 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
3549 completely disabled, and its use causes an immediate error exit.
3551 If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a
3552 colon-separated list of macros which are considered safe and, if &%-D%& only
3553 supplies macros from this list, and the values are acceptable, then Exim will
3554 not give up root privilege if the caller is root, the Exim run-time user, or
3555 the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected
3556 to be removed in the future. Acceptable values for the macros satisfy the
3557 regexp: &`^[A-Za-z0-9_/.-]*$`&
3559 The entire option (including equals sign if present) must all be within one
3560 command line item. &%-D%& can be used to set the value of a macro to the empty
3561 string, in which case the equals sign is optional. These two commands are
3567 To include spaces in a macro definition item, quotes must be used. If you use
3568 quotes, spaces are permitted around the macro name and the equals sign. For
3571 exim '-D ABC = something' ...
3573 &%-D%& may be repeated up to 10 times on a command line.
3574 Only macro names up to 22 letters long can be set.
3577 .vitem &%-d%&<&'debug&~options'&>
3579 .cindex "debugging" "list of selectors"
3580 .cindex "debugging" "&%-d%& option"
3581 This option causes debugging information to be written to the standard
3582 error stream. It is restricted to admin users because debugging output may show
3583 database queries that contain password information. Also, the details of users'
3584 filter files should be protected. If a non-admin user uses &%-d%&, Exim
3585 writes an error message to the standard error stream and exits with a non-zero
3588 When &%-d%& is used, &%-v%& is assumed. If &%-d%& is given on its own, a lot of
3589 standard debugging data is output. This can be reduced, or increased to include
3590 some more rarely needed information, by directly following &%-d%& with a string
3591 made up of names preceded by plus or minus characters. These add or remove sets
3592 of debugging data, respectively. For example, &%-d+filter%& adds filter
3593 debugging, whereas &%-d-all+filter%& selects only filter debugging. Note that
3594 no spaces are allowed in the debug setting. The available debugging categories
3597 &`acl `& ACL interpretation
3598 &`auth `& authenticators
3599 &`deliver `& general delivery logic
3600 &`dns `& DNS lookups (see also resolver)
3601 &`dnsbl `& DNS black list (aka RBL) code
3602 &`exec `& arguments for &[execv()]& calls
3603 &`expand `& detailed debugging for string expansions
3604 &`filter `& filter handling
3605 &`hints_lookup `& hints data lookups
3606 &`host_lookup `& all types of name-to-IP address handling
3607 &`ident `& ident lookup
3608 &`interface `& lists of local interfaces
3609 &`lists `& matching things in lists
3610 &`load `& system load checks
3611 &`local_scan `& can be used by &[local_scan()]& (see chapter &&&
3612 &<<CHAPlocalscan>>&)
3613 &`lookup `& general lookup code and all lookups
3614 &`memory `& memory handling
3615 &`pid `& add pid to debug output lines
3616 &`process_info `& setting info for the process log
3617 &`queue_run `& queue runs
3618 &`receive `& general message reception logic
3619 &`resolver `& turn on the DNS resolver's debugging output
3620 &`retry `& retry handling
3621 &`rewrite `& address rewriting
3622 &`route `& address routing
3623 &`timestamp `& add timestamp to debug output lines
3625 &`transport `& transports
3626 &`uid `& changes of uid/gid and looking up uid/gid
3627 &`verify `& address verification logic
3628 &`all `& almost all of the above (see below), and also &%-v%&
3630 The &`all`& option excludes &`memory`& when used as &`+all`&, but includes it
3631 for &`-all`&. The reason for this is that &`+all`& is something that people
3632 tend to use when generating debug output for Exim maintainers. If &`+memory`&
3633 is included, an awful lot of output that is very rarely of interest is
3634 generated, so it now has to be explicitly requested. However, &`-all`& does
3635 turn everything off.
3637 .cindex "resolver, debugging output"
3638 .cindex "DNS resolver, debugging output"
3639 The &`resolver`& option produces output only if the DNS resolver was compiled
3640 with DEBUG enabled. This is not the case in some operating systems. Also,
3641 unfortunately, debugging output from the DNS resolver is written to stdout
3644 The default (&%-d%& with no argument) omits &`expand`&, &`filter`&,
3645 &`interface`&, &`load`&, &`memory`&, &`pid`&, &`resolver`&, and &`timestamp`&.
3646 However, the &`pid`& selector is forced when debugging is turned on for a
3647 daemon, which then passes it on to any re-executed Exims. Exim also
3648 automatically adds the pid to debug lines when several remote deliveries are
3651 The &`timestamp`& selector causes the current time to be inserted at the start
3652 of all debug output lines. This can be useful when trying to track down delays
3655 If the &%debug_print%& option is set in any driver, it produces output whenever
3656 any debugging is selected, or if &%-v%& is used.
3658 .vitem &%-dd%&<&'debug&~options'&>
3660 This option behaves exactly like &%-d%& except when used on a command that
3661 starts a daemon process. In that case, debugging is turned off for the
3662 subprocesses that the daemon creates. Thus, it is useful for monitoring the
3663 behaviour of the daemon without creating as much output as full debugging does.
3666 .oindex "&%-dropcr%&"
3667 This is an obsolete option that is now a no-op. It used to affect the way Exim
3668 handled CR and LF characters in incoming messages. What happens now is
3669 described in section &<<SECTlineendings>>&.
3673 .cindex "bounce message" "generating"
3674 This option specifies that an incoming message is a locally-generated delivery
3675 failure report. It is used internally by Exim when handling delivery failures
3676 and is not intended for external use. Its only effect is to stop Exim
3677 generating certain messages to the postmaster, as otherwise message cascades
3678 could occur in some situations. As part of the same option, a message id may
3679 follow the characters &%-E%&. If it does, the log entry for the receipt of the
3680 new message contains the id, following &"R="&, as a cross-reference.
3683 .oindex "&%-e%&&'x'&"
3684 There are a number of Sendmail options starting with &%-oe%& which seem to be
3685 called by various programs without the leading &%o%& in the option. For
3686 example, the &%vacation%& program uses &%-eq%&. Exim treats all options of the
3687 form &%-e%&&'x'& as synonymous with the corresponding &%-oe%&&'x'& options.
3689 .vitem &%-F%&&~<&'string'&>
3691 .cindex "sender" "name"
3692 .cindex "name" "of sender"
3693 This option sets the sender's full name for use when a locally-generated
3694 message is being accepted. In the absence of this option, the user's &'gecos'&
3695 entry from the password data is used. As users are generally permitted to alter
3696 their &'gecos'& entries, no security considerations are involved. White space
3697 between &%-F%& and the <&'string'&> is optional.
3699 .vitem &%-f%&&~<&'address'&>
3701 .cindex "sender" "address"
3702 .cindex "address" "sender"
3703 .cindex "trusted users"
3704 .cindex "envelope sender"
3705 .cindex "user" "trusted"
3706 This option sets the address of the envelope sender of a locally-generated
3707 message (also known as the return path). The option can normally be used only
3708 by a trusted user, but &%untrusted_set_sender%& can be set to allow untrusted
3711 Processes running as root or the Exim user are always trusted. Other
3712 trusted users are defined by the &%trusted_users%& or &%trusted_groups%&
3713 options. In the absence of &%-f%&, or if the caller is not trusted, the sender
3714 of a local message is set to the caller's login name at the default qualify
3717 There is one exception to the restriction on the use of &%-f%&: an empty sender
3718 can be specified by any user, trusted or not, to create a message that can
3719 never provoke a bounce. An empty sender can be specified either as an empty
3720 string, or as a pair of angle brackets with nothing between them, as in these
3721 examples of shell commands:
3723 exim -f '<>' user@domain
3724 exim -f "" user@domain
3726 In addition, the use of &%-f%& is not restricted when testing a filter file
3727 with &%-bf%& or when testing or verifying addresses using the &%-bt%& or
3730 Allowing untrusted users to change the sender address does not of itself make
3731 it possible to send anonymous mail. Exim still checks that the &'From:'& header
3732 refers to the local user, and if it does not, it adds a &'Sender:'& header,
3733 though this can be overridden by setting &%no_local_from_check%&.
3736 .cindex "&""From""& line"
3737 space between &%-f%& and the <&'address'&> is optional (that is, they can be
3738 given as two arguments or one combined argument). The sender of a
3739 locally-generated message can also be set (when permitted) by an initial
3740 &"From&~"& line in the message &-- see the description of &%-bm%& above &-- but
3741 if &%-f%& is also present, it overrides &"From&~"&.
3745 .cindex "submission fixups, suppressing (command-line)"
3746 This option is equivalent to an ACL applying:
3748 control = suppress_local_fixups
3750 for every message received. Note that Sendmail will complain about such
3751 bad formatting, where Exim silently just does not fix it up. This may change
3754 As this affects audit information, the caller must be a trusted user to use
3757 .vitem &%-h%&&~<&'number'&>
3759 .cindex "Sendmail compatibility" "&%-h%& option ignored"
3760 This option is accepted for compatibility with Sendmail, but has no effect. (In
3761 Sendmail it overrides the &"hop count"& obtained by counting &'Received:'&
3766 .cindex "Solaris" "&'mail'& command"
3767 .cindex "dot" "in incoming non-SMTP message"
3768 This option, which has the same effect as &%-oi%&, specifies that a dot on a
3769 line by itself should not terminate an incoming, non-SMTP message. I can find
3770 no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
3771 command in Solaris 2.4 uses it. See also &%-ti%&.
3773 .vitem &%-L%&&~<&'tag'&>
3775 .cindex "syslog" "process name; set with flag"
3776 This option is equivalent to setting &%syslog_processname%& in the config
3777 file and setting &%log_file_path%& to &`syslog`&.
3778 Its use is restricted to administrators. The configuration file has to be
3779 read and parsed, to determine access rights, before this is set and takes
3780 effect, so early configuration file errors will not honour this flag.
3782 The tag should not be longer than 32 characters.
3784 .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3786 .cindex "forcing delivery"
3787 .cindex "delivery" "forcing attempt"
3788 .cindex "frozen messages" "forcing delivery"
3789 This option requests Exim to run a delivery attempt on each message in turn. If
3790 any of the messages are frozen, they are automatically thawed before the
3791 delivery attempt. The settings of &%queue_domains%&, &%queue_smtp_domains%&,
3792 and &%hold_domains%& are ignored.
3795 .cindex "hints database" "overriding retry hints"
3796 hints for any of the addresses are overridden &-- Exim tries to deliver even if
3797 the normal retry time has not yet been reached. This option requires the caller
3798 to be an admin user. However, there is an option called &%prod_requires_admin%&
3799 which can be set false to relax this restriction (and also the same requirement
3800 for the &%-q%&, &%-R%&, and &%-S%& options).
3802 The deliveries happen synchronously, that is, the original Exim process does
3803 not terminate until all the delivery attempts have finished. No output is
3804 produced unless there is a serious error. If you want to see what is happening,
3805 use the &%-v%& option as well, or inspect Exim's main log.
3807 .vitem &%-Mar%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3809 .cindex "message" "adding recipients"
3810 .cindex "recipient" "adding"
3811 This option requests Exim to add the addresses to the list of recipients of the
3812 message (&"ar"& for &"add recipients"&). The first argument must be a message
3813 id, and the remaining ones must be email addresses. However, if the message is
3814 active (in the middle of a delivery attempt), it is not altered. This option
3815 can be used only by an admin user.
3817 .vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
3818 &~<&'message&~id'&>"
3820 .cindex "SMTP" "passed connection"
3821 .cindex "SMTP" "multiple deliveries"
3822 .cindex "multiple SMTP deliveries"
3823 This option is not intended for use by external callers. It is used internally
3824 by Exim to invoke another instance of itself to deliver a waiting message using
3825 an existing SMTP connection, which is passed as the standard input. Details are
3826 given in chapter &<<CHAPSMTP>>&. This must be the final option, and the caller
3827 must be root or the Exim user in order to use it.
3831 This option is not intended for use by external callers. It is used internally
3832 by Exim in conjunction with the &%-MC%& option. It signifies that the
3833 connection to the remote host has been authenticated.
3837 This option is not intended for use by external callers. It is used internally
3838 by Exim in conjunction with the &%-MC%& option. It signifies that the
3839 remote host supports the ESMTP &_DSN_& extension.
3841 .vitem &%-MCG%&&~<&'queue&~name'&>
3843 This option is not intended for use by external callers. It is used internally
3844 by Exim in conjunction with the &%-MC%& option. It signifies that an
3845 alternate queue is used, named by the following argument.
3849 This option is not intended for use by external callers. It is used internally
3850 by Exim in conjunction with the &%-MC%& option. It signifies that a
3851 remote host supports the ESMTP &_CHUNKING_& extension.
3855 This option is not intended for use by external callers. It is used internally
3856 by Exim in conjunction with the &%-MC%& option. It signifies that the server to
3857 which Exim is connected supports pipelining.
3859 .vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
3861 This option is not intended for use by external callers. It is used internally
3862 by Exim in conjunction with the &%-MC%& option when the original delivery was
3863 started by a queue runner. It passes on the process id of the queue runner,
3864 together with the file descriptor number of an open pipe. Closure of the pipe
3865 signals the final completion of the sequence of processes that are passing
3866 messages through the same SMTP connection.
3870 This option is not intended for use by external callers. It is used internally
3871 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3872 SMTP SIZE option should be used on messages delivered down the existing
3877 This option is not intended for use by external callers. It is used internally
3878 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3879 host to which Exim is connected supports TLS encryption.
3881 .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
3883 This option is not intended for use by external callers. It is used internally
3884 by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
3885 connection is being proxied by a parent process for handling TLS encryption.
3886 The arguments give the local address and port being proxied, and the TLS cipher.
3888 .vitem &%-Mc%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3890 .cindex "hints database" "not overridden by &%-Mc%&"
3891 .cindex "delivery" "manually started &-- not forced"
3892 This option requests Exim to run a delivery attempt on each message in turn,
3893 but unlike the &%-M%& option, it does check for retry hints, and respects any
3894 that are found. This option is not very useful to external callers. It is
3895 provided mainly for internal use by Exim when it needs to re-invoke itself in
3896 order to regain root privilege for a delivery (see chapter &<<CHAPsecurity>>&).
3897 However, &%-Mc%& can be useful when testing, in order to run a delivery that
3898 respects retry times and other options such as &%hold_domains%& that are
3899 overridden when &%-M%& is used. Such a delivery does not count as a queue run.
3900 If you want to run a specific delivery as if in a queue run, you should use
3901 &%-q%& with a message id argument. A distinction between queue run deliveries
3902 and other deliveries is made in one or two places.
3904 .vitem &%-Mes%&&~<&'message&~id'&>&~<&'address'&>
3906 .cindex "message" "changing sender"
3907 .cindex "sender" "changing"
3908 This option requests Exim to change the sender address in the message to the
3909 given address, which must be a fully qualified address or &"<>"& (&"es"& for
3910 &"edit sender"&). There must be exactly two arguments. The first argument must
3911 be a message id, and the second one an email address. However, if the message
3912 is active (in the middle of a delivery attempt), its status is not altered.
3913 This option can be used only by an admin user.
3915 .vitem &%-Mf%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3917 .cindex "freezing messages"
3918 .cindex "message" "manually freezing"
3919 This option requests Exim to mark each listed message as &"frozen"&. This
3920 prevents any delivery attempts taking place until the message is &"thawed"&,
3921 either manually or as a result of the &%auto_thaw%& configuration option.
3922 However, if any of the messages are active (in the middle of a delivery
3923 attempt), their status is not altered. This option can be used only by an admin
3926 .vitem &%-Mg%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3928 .cindex "giving up on messages"
3929 .cindex "message" "abandoning delivery attempts"
3930 .cindex "delivery" "abandoning further attempts"
3931 This option requests Exim to give up trying to deliver the listed messages,
3932 including any that are frozen. However, if any of the messages are active,
3933 their status is not altered. For non-bounce messages, a delivery error message
3934 is sent to the sender, containing the text &"cancelled by administrator"&.
3935 Bounce messages are just discarded. This option can be used only by an admin
3938 .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3940 .cindex "delivery" "cancelling all"
3941 This option requests Exim to mark all the recipient addresses in the messages
3942 as already delivered (&"mad"& for &"mark all delivered"&). However, if any
3943 message is active (in the middle of a delivery attempt), its status is not
3944 altered. This option can be used only by an admin user.
3946 .vitem &%-Mmd%&&~<&'message&~id'&>&~<&'address'&>&~<&'address'&>&~...
3948 .cindex "delivery" "cancelling by address"
3949 .cindex "recipient" "removing"
3950 .cindex "removing recipients"
3951 This option requests Exim to mark the given addresses as already delivered
3952 (&"md"& for &"mark delivered"&). The first argument must be a message id, and
3953 the remaining ones must be email addresses. These are matched to recipient
3954 addresses in the message in a case-sensitive manner. If the message is active
3955 (in the middle of a delivery attempt), its status is not altered. This option
3956 can be used only by an admin user.
3958 .vitem &%-Mrm%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3960 .cindex "removing messages"
3961 .cindex "abandoning mail"
3962 .cindex "message" "manually discarding"
3963 This option requests Exim to remove the given messages from the queue. No
3964 bounce messages are sent; each message is simply forgotten. However, if any of
3965 the messages are active, their status is not altered. This option can be used
3966 only by an admin user or by the user who originally caused the message to be
3967 placed on the queue.
3969 .vitem &%-Mset%&&~<&'message&~id'&>
3971 .cindex "testing" "string expansion"
3972 .cindex "expansion" "testing"
3973 This option is useful only in conjunction with &%-be%& (that is, when testing
3974 string expansions). Exim loads the given message from its spool before doing
3975 the test expansions, thus setting message-specific variables such as
3976 &$message_size$& and the header variables. The &$recipients$& variable is made
3977 available. This feature is provided to make it easier to test expansions that
3978 make use of these variables. However, this option can be used only by an admin
3979 user. See also &%-bem%&.
3981 .vitem &%-Mt%&&~<&'message&~id'&>&~<&'message&~id'&>&~...
3983 .cindex "thawing messages"
3984 .cindex "unfreezing messages"
3985 .cindex "frozen messages" "thawing"
3986 .cindex "message" "thawing frozen"
3987 This option requests Exim to &"thaw"& any of the listed messages that are
3988 &"frozen"&, so that delivery attempts can resume. However, if any of the
3989 messages are active, their status is not altered. This option can be used only
3992 .vitem &%-Mvb%&&~<&'message&~id'&>
3994 .cindex "listing" "message body"
3995 .cindex "message" "listing body of"
3996 This option causes the contents of the message body (-D) spool file to be
3997 written to the standard output. This option can be used only by an admin user.
3999 .vitem &%-Mvc%&&~<&'message&~id'&>
4001 .cindex "message" "listing in RFC 2822 format"
4002 .cindex "listing" "message in RFC 2822 format"
4003 This option causes a copy of the complete message (header lines plus body) to
4004 be written to the standard output in RFC 2822 format. This option can be used
4005 only by an admin user.
4007 .vitem &%-Mvh%&&~<&'message&~id'&>
4009 .cindex "listing" "message headers"
4010 .cindex "header lines" "listing"
4011 .cindex "message" "listing header lines"
4012 This option causes the contents of the message headers (-H) spool file to be
4013 written to the standard output. This option can be used only by an admin user.
4015 .vitem &%-Mvl%&&~<&'message&~id'&>
4017 .cindex "listing" "message log"
4018 .cindex "message" "listing message log"
4019 This option causes the contents of the message log spool file to be written to
4020 the standard output. This option can be used only by an admin user.
4024 This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
4025 treats it that way too.
4029 .cindex "debugging" "&%-N%& option"
4030 .cindex "debugging" "suppressing delivery"
4031 This is a debugging option that inhibits delivery of a message at the transport
4032 level. It implies &%-v%&. Exim goes through many of the motions of delivery &--
4033 it just doesn't actually transport the message, but instead behaves as if it
4034 had successfully done so. However, it does not make any updates to the retry
4035 database, and the log entries for deliveries are flagged with &"*>"& rather
4038 Because &%-N%& discards any message to which it applies, only root or the Exim
4039 user are allowed to use it with &%-bd%&, &%-q%&, &%-R%& or &%-M%&. In other
4040 words, an ordinary user can use it only when supplying an incoming message to
4041 which it will apply. Although transportation never fails when &%-N%& is set, an
4042 address may be deferred because of a configuration problem on a transport, or a
4043 routing problem. Once &%-N%& has been used for a delivery attempt, it sticks to
4044 the message, and applies to any subsequent delivery attempts that may happen
4049 This option is interpreted by Sendmail to mean &"no aliasing"&.
4050 For normal modes of operation, it is ignored by Exim.
4051 When combined with &%-bP%& it makes the output more terse (suppresses
4052 option names, environment values and config pretty printing).
4054 .vitem &%-O%&&~<&'data'&>
4056 This option is interpreted by Sendmail to mean &`set option`&. It is ignored by
4059 .vitem &%-oA%&&~<&'file&~name'&>
4061 .cindex "Sendmail compatibility" "&%-oA%& option"
4062 This option is used by Sendmail in conjunction with &%-bi%& to specify an
4063 alternative alias file name. Exim handles &%-bi%& differently; see the
4066 .vitem &%-oB%&&~<&'n'&>
4068 .cindex "SMTP" "passed connection"
4069 .cindex "SMTP" "multiple deliveries"
4070 .cindex "multiple SMTP deliveries"
4071 This is a debugging option which limits the maximum number of messages that can
4072 be delivered down one SMTP connection, overriding the value set in any &(smtp)&
4073 transport. If <&'n'&> is omitted, the limit is set to 1.
4077 .cindex "background delivery"
4078 .cindex "delivery" "in the background"
4079 This option applies to all modes in which Exim accepts incoming messages,
4080 including the listening daemon. It requests &"background"& delivery of such
4081 messages, which means that the accepting process automatically starts a
4082 delivery process for each message received, but does not wait for the delivery
4083 processes to finish.
4085 When all the messages have been received, the reception process exits,
4086 leaving the delivery processes to finish in their own time. The standard output
4087 and error streams are closed at the start of each delivery process.
4088 This is the default action if none of the &%-od%& options are present.
4090 If one of the queueing options in the configuration file
4091 (&%queue_only%& or &%queue_only_file%&, for example) is in effect, &%-odb%&
4092 overrides it if &%queue_only_override%& is set true, which is the default
4093 setting. If &%queue_only_override%& is set false, &%-odb%& has no effect.
4097 .cindex "foreground delivery"
4098 .cindex "delivery" "in the foreground"
4099 This option requests &"foreground"& (synchronous) delivery when Exim has
4100 accepted a locally-generated message. (For the daemon it is exactly the same as
4101 &%-odb%&.) A delivery process is automatically started to deliver the message,
4102 and Exim waits for it to complete before proceeding.
4104 The original Exim reception process does not finish until the delivery
4105 process for the final message has ended. The standard error stream is left open
4108 However, like &%-odb%&, this option has no effect if &%queue_only_override%& is
4109 false and one of the queueing options in the configuration file is in effect.
4111 If there is a temporary delivery error during foreground delivery, the
4112 message is left on the queue for later delivery, and the original reception
4113 process exits. See chapter &<<CHAPnonqueueing>>& for a way of setting up a
4114 restricted configuration that never queues messages.
4119 This option is synonymous with &%-odf%&. It is provided for compatibility with
4124 .cindex "non-immediate delivery"
4125 .cindex "delivery" "suppressing immediate"
4126 .cindex "queueing incoming messages"
4127 This option applies to all modes in which Exim accepts incoming messages,
4128 including the listening daemon. It specifies that the accepting process should
4129 not automatically start a delivery process for each message received. Messages
4130 are placed on the queue, and remain there until a subsequent queue runner
4131 process encounters them. There are several configuration options (such as
4132 &%queue_only%&) that can be used to queue incoming messages under certain
4133 conditions. This option overrides all of them and also &%-odqs%&. It always
4138 .cindex "SMTP" "delaying delivery"
4139 This option is a hybrid between &%-odb%&/&%-odi%& and &%-odq%&.
4140 However, like &%-odb%& and &%-odi%&, this option has no effect if
4141 &%queue_only_override%& is false and one of the queueing options in the
4142 configuration file is in effect.
4144 When &%-odqs%& does operate, a delivery process is started for each incoming
4145 message, in the background by default, but in the foreground if &%-odi%& is
4146 also present. The recipient addresses are routed, and local deliveries are done
4147 in the normal way. However, if any SMTP deliveries are required, they are not
4148 done at this time, so the message remains on the queue until a subsequent queue
4149 runner process encounters it. Because routing was done, Exim knows which
4150 messages are waiting for which hosts, and so a number of messages for the same
4151 host can be sent in a single SMTP connection. The &%queue_smtp_domains%&
4152 configuration option has the same effect for specific domains. See also the
4157 .cindex "error" "reporting"
4158 If an error is detected while a non-SMTP message is being received (for
4159 example, a malformed address), the error is reported to the sender in a mail
4162 .cindex "return code" "for &%-oee%&"
4164 this error message is successfully sent, the Exim receiving process
4165 exits with a return code of zero. If not, the return code is 2 if the problem
4166 is that the original message has no recipients, or 1 for any other error.
4167 This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&.
4171 .cindex "error" "reporting"
4172 .cindex "return code" "for &%-oem%&"
4173 This is the same as &%-oee%&, except that Exim always exits with a non-zero
4174 return code, whether or not the error message was successfully sent.
4175 This is the default &%-oe%&&'x'& option, unless Exim is called as &'rmail'&.
4179 .cindex "error" "reporting"
4180 If an error is detected while a non-SMTP message is being received, the
4181 error is reported by writing a message to the standard error file (stderr).
4182 .cindex "return code" "for &%-oep%&"
4183 The return code is 1 for all errors.
4187 .cindex "error" "reporting"
4188 This option is supported for compatibility with Sendmail, but has the same
4193 .cindex "error" "reporting"
4194 This option is supported for compatibility with Sendmail, but has the same
4199 .cindex "dot" "in incoming non-SMTP message"
4200 This option, which has the same effect as &%-i%&, specifies that a dot on a
4201 line by itself should not terminate an incoming, non-SMTP message. Otherwise, a
4202 single dot does terminate, though Exim does no special processing for other
4203 lines that start with a dot. This option is set by default if Exim is called as
4204 &'rmail'&. See also &%-ti%&.
4207 .oindex "&%-oitrue%&"
4208 This option is treated as synonymous with &%-oi%&.
4210 .vitem &%-oMa%&&~<&'host&~address'&>
4212 .cindex "sender" "host address, specifying for local message"
4213 A number of options starting with &%-oM%& can be used to set values associated
4214 with remote hosts on locally-submitted messages (that is, messages not received
4215 over TCP/IP). These options can be used by any caller in conjunction with the
4216 &%-bh%&, &%-be%&, &%-bf%&, &%-bF%&, &%-bt%&, or &%-bv%& testing options. In
4217 other circumstances, they are ignored unless the caller is trusted.
4219 The &%-oMa%& option sets the sender host address. This may include a port
4220 number at the end, after a full stop (period). For example:
4222 exim -bs -oMa 10.9.8.7.1234
4224 An alternative syntax is to enclose the IP address in square brackets,
4225 followed by a colon and the port number:
4227 exim -bs -oMa [10.9.8.7]:1234
4229 The IP address is placed in the &$sender_host_address$& variable, and the
4230 port, if present, in &$sender_host_port$&. If both &%-oMa%& and &%-bh%&
4231 are present on the command line, the sender host IP address is taken from
4232 whichever one is last.
4234 .vitem &%-oMaa%&&~<&'name'&>
4236 .cindex "authentication" "name, specifying for local message"
4237 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMaa%&
4238 option sets the value of &$sender_host_authenticated$& (the authenticator
4239 name). See chapter &<<CHAPSMTPAUTH>>& for a discussion of SMTP authentication.
4240 This option can be used with &%-bh%& and &%-bs%& to set up an
4241 authenticated SMTP session without actually using the SMTP AUTH command.
4243 .vitem &%-oMai%&&~<&'string'&>
4245 .cindex "authentication" "id, specifying for local message"
4246 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMai%&
4247 option sets the value of &$authenticated_id$& (the id that was authenticated).
4248 This overrides the default value (the caller's login id, except with &%-bh%&,
4249 where there is no default) for messages from local sources. See chapter
4250 &<<CHAPSMTPAUTH>>& for a discussion of authenticated ids.
4252 .vitem &%-oMas%&&~<&'address'&>
4254 .cindex "authentication" "sender, specifying for local message"
4255 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMas%&
4256 option sets the authenticated sender value in &$authenticated_sender$&. It
4257 overrides the sender address that is created from the caller's login id for
4258 messages from local sources, except when &%-bh%& is used, when there is no
4259 default. For both &%-bh%& and &%-bs%&, an authenticated sender that is
4260 specified on a MAIL command overrides this value. See chapter
4261 &<<CHAPSMTPAUTH>>& for a discussion of authenticated senders.
4263 .vitem &%-oMi%&&~<&'interface&~address'&>
4265 .cindex "interface" "address, specifying for local message"
4266 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMi%&
4267 option sets the IP interface address value. A port number may be included,
4268 using the same syntax as for &%-oMa%&. The interface address is placed in
4269 &$received_ip_address$& and the port number, if present, in &$received_port$&.
4271 .vitem &%-oMm%&&~<&'message&~reference'&>
4273 .cindex "message reference" "message reference, specifying for local message"
4274 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMm%&
4275 option sets the message reference, e.g. message-id, and is logged during
4276 delivery. This is useful when some kind of audit trail is required to tie
4277 messages together. The format of the message reference is checked and will
4278 abort if the format is invalid. The option will only be accepted if exim is
4279 running in trusted mode, not as any regular user.
4281 The best example of a message reference is when Exim sends a bounce message.
4282 The message reference is the message-id of the original message for which Exim
4283 is sending the bounce.
4285 .vitem &%-oMr%&&~<&'protocol&~name'&>
4287 .cindex "protocol, specifying for local message"
4288 .vindex "&$received_protocol$&"
4289 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMr%&
4290 option sets the received protocol value that is stored in
4291 &$received_protocol$&. However, it does not apply (and is ignored) when &%-bh%&
4292 or &%-bs%& is used. For &%-bh%&, the protocol is forced to one of the standard
4293 SMTP protocol names (see the description of &$received_protocol$& in section
4294 &<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
4295 one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
4296 be set by &%-oMr%&. Repeated use of this option is not supported.
4298 .vitem &%-oMs%&&~<&'host&~name'&>
4300 .cindex "sender" "host name, specifying for local message"
4301 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMs%&
4302 option sets the sender host name in &$sender_host_name$&. When this option is
4303 present, Exim does not attempt to look up a host name from an IP address; it
4304 uses the name it is given.
4306 .vitem &%-oMt%&&~<&'ident&~string'&>
4308 .cindex "sender" "ident string, specifying for local message"
4309 See &%-oMa%& above for general remarks about the &%-oM%& options. The &%-oMt%&
4310 option sets the sender ident value in &$sender_ident$&. The default setting for
4311 local callers is the login id of the calling process, except when &%-bh%& is
4312 used, when there is no default.
4316 .cindex "Sendmail compatibility" "&%-om%& option ignored"
4317 In Sendmail, this option means &"me too"&, indicating that the sender of a
4318 message should receive a copy of the message if the sender appears in an alias
4319 expansion. Exim always does this, so the option does nothing.
4323 .cindex "Sendmail compatibility" "&%-oo%& option ignored"
4324 This option is ignored. In Sendmail it specifies &"old style headers"&,
4325 whatever that means.
4327 .vitem &%-oP%&&~<&'path'&>
4329 .cindex "pid (process id)" "of daemon"
4330 .cindex "daemon" "process id (pid)"
4331 This option is useful only in conjunction with &%-bd%& or &%-q%& with a time
4332 value. The option specifies the file to which the process id of the daemon is
4333 written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used
4334 without &%-bd%&, this is the only way of causing Exim to write a pid file,
4335 because in those cases, the normal pid file is not used.
4337 .vitem &%-or%&&~<&'time'&>
4339 .cindex "timeout" "for non-SMTP input"
4340 This option sets a timeout value for incoming non-SMTP messages. If it is not
4341 set, Exim will wait forever for the standard input. The value can also be set
4342 by the &%receive_timeout%& option. The format used for specifying times is
4343 described in section &<<SECTtimeformat>>&.
4345 .vitem &%-os%&&~<&'time'&>
4347 .cindex "timeout" "for SMTP input"
4348 .cindex "SMTP" "input timeout"
4349 This option sets a timeout value for incoming SMTP messages. The timeout
4350 applies to each SMTP command and block of data. The value can also be set by
4351 the &%smtp_receive_timeout%& option; it defaults to 5 minutes. The format used
4352 for specifying times is described in section &<<SECTtimeformat>>&.
4356 This option has exactly the same effect as &%-v%&.
4358 .vitem &%-oX%&&~<&'number&~or&~string'&>
4360 .cindex "TCP/IP" "setting listening ports"
4361 .cindex "TCP/IP" "setting listening interfaces"
4362 .cindex "port" "receiving TCP/IP"
4363 This option is relevant only when the &%-bd%& (start listening daemon) option
4364 is also given. It controls which ports and interfaces the daemon uses. Details
4365 of the syntax, and how it interacts with configuration file options, are given
4366 in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
4367 file is written unless &%-oP%& is also present to specify a pid file name.
4371 .cindex "Perl" "starting the interpreter"
4372 This option applies when an embedded Perl interpreter is linked with Exim (see
4373 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4374 option, forcing the starting of the interpreter to be delayed until it is
4379 .cindex "Perl" "starting the interpreter"
4380 This option applies when an embedded Perl interpreter is linked with Exim (see
4381 chapter &<<CHAPperl>>&). It overrides the setting of the &%perl_at_start%&
4382 option, forcing the starting of the interpreter to occur as soon as Exim is
4385 .vitem &%-p%&<&'rval'&>:<&'sval'&>
4387 For compatibility with Sendmail, this option is equivalent to
4389 &`-oMr`& <&'rval'&> &`-oMs`& <&'sval'&>
4391 It sets the incoming protocol and host name (for trusted callers). The
4392 host name and its colon can be omitted when only the protocol is to be set.
4393 Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
4394 to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
4395 or &`s`& using this option (but that does not seem a real limitation).
4396 Repeated use of this option is not supported.
4400 .cindex "queue runner" "starting manually"
4401 This option is normally restricted to admin users. However, there is a
4402 configuration option called &%prod_requires_admin%& which can be set false to
4403 relax this restriction (and also the same requirement for the &%-M%&, &%-R%&,
4404 and &%-S%& options).
4406 .cindex "queue runner" "description of operation"
4407 If other commandline options do not specify an action,
4408 the &%-q%& option starts one queue runner process. This scans the queue of
4409 waiting messages, and runs a delivery process for each one in turn. It waits
4410 for each delivery process to finish before starting the next one. A delivery
4411 process may not actually do any deliveries if the retry times for the addresses
4412 have not been reached. Use &%-qf%& (see below) if you want to override this.
4415 .cindex "SMTP" "passed connection"
4416 .cindex "SMTP" "multiple deliveries"
4417 .cindex "multiple SMTP deliveries"
4418 the delivery process spawns other processes to deliver other messages down
4419 passed SMTP connections, the queue runner waits for these to finish before
4422 When all the queued messages have been considered, the original queue runner
4423 process terminates. In other words, a single pass is made over the waiting
4424 mail, one message at a time. Use &%-q%& with a time (see below) if you want
4425 this to be repeated periodically.
4427 Exim processes the waiting messages in an unpredictable order. It isn't very
4428 random, but it is likely to be different each time, which is all that matters.
4429 If one particular message screws up a remote MTA, other messages to the same
4430 MTA have a chance of getting through if they get tried first.
4432 It is possible to cause the messages to be processed in lexical message id
4433 order, which is essentially the order in which they arrived, by setting the
4434 &%queue_run_in_order%& option, but this is not recommended for normal use.
4436 .vitem &%-q%&<&'qflags'&>
4437 The &%-q%& option may be followed by one or more flag letters that change its
4438 behaviour. They are all optional, but if more than one is present, they must
4439 appear in the correct order. Each flag is described in a separate item below.
4443 .cindex "queue" "double scanning"
4444 .cindex "queue" "routing"
4445 .cindex "routing" "whole queue before delivery"
4446 An option starting with &%-qq%& requests a two-stage queue run. In the first
4447 stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
4448 every domain. Addresses are routed, local deliveries happen, but no remote
4451 .cindex "hints database" "remembering routing"
4452 The hints database that remembers which messages are waiting for specific hosts
4453 is updated, as if delivery to those hosts had been deferred. After this is
4454 complete, a second, normal queue scan happens, with routing and delivery taking
4455 place as normal. Messages that are routed to the same host should mostly be
4456 delivered down a single SMTP
4457 .cindex "SMTP" "passed connection"
4458 .cindex "SMTP" "multiple deliveries"
4459 .cindex "multiple SMTP deliveries"
4460 connection because of the hints that were set up during the first queue scan.
4461 This option may be useful for hosts that are connected to the Internet
4464 .vitem &%-q[q]i...%&
4466 .cindex "queue" "initial delivery"
4467 If the &'i'& flag is present, the queue runner runs delivery processes only for
4468 those messages that haven't previously been tried. (&'i'& stands for &"initial
4469 delivery"&.) This can be helpful if you are putting messages on the queue using
4470 &%-odq%& and want a queue runner just to process the new messages.
4472 .vitem &%-q[q][i]f...%&
4474 .cindex "queue" "forcing delivery"
4475 .cindex "delivery" "forcing in queue run"
4476 If one &'f'& flag is present, a delivery attempt is forced for each non-frozen
4477 message, whereas without &'f'& only those non-frozen addresses that have passed
4478 their retry times are tried.
4480 .vitem &%-q[q][i]ff...%&
4482 .cindex "frozen messages" "forcing delivery"
4483 If &'ff'& is present, a delivery attempt is forced for every message, whether
4486 .vitem &%-q[q][i][f[f]]l%&
4488 .cindex "queue" "local deliveries only"
4489 The &'l'& (the letter &"ell"&) flag specifies that only local deliveries are to
4490 be done. If a message requires any remote deliveries, it remains on the queue
4493 .vitem &%-q[q][i][f[f]][l][G<name>[/<time>]]]%&
4496 .cindex "named queues"
4497 .cindex "queue" "delivering specific messages"
4498 If the &'G'& flag and a name is present, the queue runner operates on the
4499 queue with the given name rather than the default queue.
4500 The name should not contain a &'/'& character.
4501 For a periodic queue run (see below)
4502 append to the name a slash and a time value.
4504 If other commandline options specify an action, a &'-qG<name>'& option
4505 will specify a queue to operate on.
4508 exim -bp -qGquarantine
4510 exim -qGoffpeak -Rf @special.domain.example
4513 .vitem &%-q%&<&'qflags'&>&~<&'start&~id'&>&~<&'end&~id'&>
4514 When scanning the queue, Exim can be made to skip over messages whose ids are
4515 lexically less than a given value by following the &%-q%& option with a
4516 starting message id. For example:
4518 exim -q 0t5C6f-0000c8-00
4520 Messages that arrived earlier than &`0t5C6f-0000c8-00`& are not inspected. If a
4521 second message id is given, messages whose ids are lexically greater than it
4522 are also skipped. If the same id is given twice, for example,
4524 exim -q 0t5C6f-0000c8-00 0t5C6f-0000c8-00
4526 just one delivery process is started, for that message. This differs from
4527 &%-M%& in that retry data is respected, and it also differs from &%-Mc%& in
4528 that it counts as a delivery from a queue run. Note that the selection
4529 mechanism does not affect the order in which the messages are scanned. There
4530 are also other ways of selecting specific sets of messages for delivery in a
4531 queue run &-- see &%-R%& and &%-S%&.
4533 .vitem &%-q%&<&'qflags'&><&'time'&>
4534 .cindex "queue runner" "starting periodically"
4535 .cindex "periodic queue running"
4536 When a time value is present, the &%-q%& option causes Exim to run as a daemon,
4537 starting a queue runner process at intervals specified by the given time value
4538 (whose format is described in section &<<SECTtimeformat>>&). This form of the
4539 &%-q%& option is commonly combined with the &%-bd%& option, in which case a
4540 single daemon process handles both functions. A common way of starting up a
4541 combined daemon at system boot time is to use a command such as
4543 /usr/exim/bin/exim -bd -q30m
4545 Such a daemon listens for incoming SMTP calls, and also starts a queue runner
4546 process every 30 minutes.
4548 When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no
4549 pid file is written unless one is explicitly requested by the &%-oP%& option.
4551 .vitem &%-qR%&<&'rsflags'&>&~<&'string'&>
4553 This option is synonymous with &%-R%&. It is provided for Sendmail
4556 .vitem &%-qS%&<&'rsflags'&>&~<&'string'&>
4558 This option is synonymous with &%-S%&.
4560 .vitem &%-R%&<&'rsflags'&>&~<&'string'&>
4562 .cindex "queue runner" "for specific recipients"
4563 .cindex "delivery" "to given domain"
4564 .cindex "domain" "delivery to"
4565 The <&'rsflags'&> may be empty, in which case the white space before the string
4566 is optional, unless the string is &'f'&, &'ff'&, &'r'&, &'rf'&, or &'rff'&,
4567 which are the possible values for <&'rsflags'&>. White space is required if
4568 <&'rsflags'&> is not empty.
4570 This option is similar to &%-q%& with no time value, that is, it causes Exim to
4571 perform a single queue run, except that, when scanning the messages on the
4572 queue, Exim processes only those that have at least one undelivered recipient
4573 address containing the given string, which is checked in a case-independent
4574 way. If the <&'rsflags'&> start with &'r'&, <&'string'&> is interpreted as a
4575 regular expression; otherwise it is a literal string.
4577 If you want to do periodic queue runs for messages with specific recipients,
4578 you can combine &%-R%& with &%-q%& and a time value. For example:
4580 exim -q25m -R @special.domain.example
4582 This example does a queue run for messages with recipients in the given domain
4583 every 25 minutes. Any additional flags that are specified with &%-q%& are
4584 applied to each queue run.
4586 Once a message is selected for delivery by this mechanism, all its addresses
4587 are processed. For the first selected message, Exim overrides any retry
4588 information and forces a delivery attempt for each undelivered address. This
4589 means that if delivery of any address in the first message is successful, any
4590 existing retry information is deleted, and so delivery attempts for that
4591 address in subsequently selected messages (which are processed without forcing)
4592 will run. However, if delivery of any address does not succeed, the retry
4593 information is updated, and in subsequently selected messages, the failing
4594 address will be skipped.
4596 .cindex "frozen messages" "forcing delivery"
4597 If the <&'rsflags'&> contain &'f'& or &'ff'&, the delivery forcing applies to
4598 all selected messages, not just the first; frozen messages are included when
4601 The &%-R%& option makes it straightforward to initiate delivery of all messages
4602 to a given domain after a host has been down for some time. When the SMTP
4603 command ETRN is accepted by its ACL (see chapter &<<CHAPACL>>&), its default
4604 effect is to run Exim with the &%-R%& option, but it can be configured to run
4605 an arbitrary command instead.
4609 This is a documented (for Sendmail) obsolete alternative name for &%-f%&.
4611 .vitem &%-S%&<&'rsflags'&>&~<&'string'&>
4613 .cindex "delivery" "from given sender"
4614 .cindex "queue runner" "for specific senders"
4615 This option acts like &%-R%& except that it checks the string against each
4616 message's sender instead of against the recipients. If &%-R%& is also set, both
4617 conditions must be met for a message to be selected. If either of the options
4618 has &'f'& or &'ff'& in its flags, the associated action is taken.
4620 .vitem &%-Tqt%&&~<&'times'&>
4622 This is an option that is exclusively for use by the Exim testing suite. It is not
4623 recognized when Exim is run normally. It allows for the setting up of explicit
4624 &"queue times"& so that various warning/retry features can be tested.
4628 .cindex "recipient" "extracting from header lines"
4629 .cindex "&'Bcc:'& header line"
4630 .cindex "&'Cc:'& header line"
4631 .cindex "&'To:'& header line"
4632 When Exim is receiving a locally-generated, non-SMTP message on its standard
4633 input, the &%-t%& option causes the recipients of the message to be obtained
4634 from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
4635 from the command arguments. The addresses are extracted before any rewriting
4636 takes place and the &'Bcc:'& header line, if present, is then removed.
4638 .cindex "Sendmail compatibility" "&%-t%& option"
4639 If the command has any arguments, they specify addresses to which the message
4640 is &'not'& to be delivered. That is, the argument addresses are removed from
4641 the recipients list obtained from the headers. This is compatible with Smail 3
4642 and in accordance with the documented behaviour of several versions of
4643 Sendmail, as described in man pages on a number of operating systems (e.g.
4644 Solaris 8, IRIX 6.5, HP-UX 11). However, some versions of Sendmail &'add'&
4645 argument addresses to those obtained from the headers, and the O'Reilly
4646 Sendmail book documents it that way. Exim can be made to add argument addresses
4647 instead of subtracting them by setting the option
4648 &%extract_addresses_remove_arguments%& false.
4650 .cindex "&%Resent-%& header lines" "with &%-t%&"
4651 If there are any &%Resent-%& header lines in the message, Exim extracts
4652 recipients from all &'Resent-To:'&, &'Resent-Cc:'&, and &'Resent-Bcc:'& header
4653 lines instead of from &'To:'&, &'Cc:'&, and &'Bcc:'&. This is for compatibility
4654 with Sendmail and other MTAs. (Prior to release 4.20, Exim gave an error if
4655 &%-t%& was used in conjunction with &%Resent-%& header lines.)
4657 RFC 2822 talks about different sets of &%Resent-%& header lines (for when a
4658 message is resent several times). The RFC also specifies that they should be
4659 added at the front of the message, and separated by &'Received:'& lines. It is
4660 not at all clear how &%-t%& should operate in the present of multiple sets,
4661 nor indeed exactly what constitutes a &"set"&.
4662 In practice, it seems that MUAs do not follow the RFC. The &%Resent-%& lines
4663 are often added at the end of the header, and if a message is resent more than
4664 once, it is common for the original set of &%Resent-%& headers to be renamed as
4665 &%X-Resent-%& when a new set is added. This removes any possible ambiguity.
4669 This option is exactly equivalent to &%-t%& &%-i%&. It is provided for
4670 compatibility with Sendmail.
4672 .vitem &%-tls-on-connect%&
4673 .oindex "&%-tls-on-connect%&"
4674 .cindex "TLS" "use without STARTTLS"
4675 .cindex "TLS" "automatic start"
4676 This option is available when Exim is compiled with TLS support. It forces all
4677 incoming SMTP connections to behave as if the incoming port is listed in the
4678 &%tls_on_connect_ports%& option. See section &<<SECTsupobssmt>>& and chapter
4679 &<<CHAPTLS>>& for further details.
4684 .cindex "Sendmail compatibility" "&%-U%& option ignored"
4685 Sendmail uses this option for &"initial message submission"&, and its
4686 documentation states that in future releases, it may complain about
4687 syntactically invalid messages rather than fixing them when this flag is not
4688 set. Exim ignores this option.
4692 This option causes Exim to write information to the standard error stream,
4693 describing what it is doing. In particular, it shows the log lines for
4694 receiving and delivering a message, and if an SMTP connection is made, the SMTP
4695 dialogue is shown. Some of the log lines shown may not actually be written to
4696 the log if the setting of &%log_selector%& discards them. Any relevant
4697 selectors are shown with each log line. If none are shown, the logging is
4702 AIX uses &%-x%& for a private purpose (&"mail from a local mail program has
4703 National Language Support extended characters in the body of the mail item"&).
4704 It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores
4707 .vitem &%-X%&&~<&'logfile'&>
4709 This option is interpreted by Sendmail to cause debug information to be sent
4710 to the named file. It is ignored by Exim.
4712 .vitem &%-z%&&~<&'log-line'&>
4714 This option writes its argument to Exim's logfile.
4715 Use is restricted to administrators; the intent is for operational notes.
4716 Quotes should be used to maintain a multi-word item as a single argument,
4724 . ////////////////////////////////////////////////////////////////////////////
4725 . Insert a stylized DocBook comment here, to identify the end of the command
4726 . line options. This is for the benefit of the Perl script that automatically
4727 . creates a man page for the options.
4728 . ////////////////////////////////////////////////////////////////////////////
4731 <!-- === End of command line options === -->
4738 . ////////////////////////////////////////////////////////////////////////////
4739 . ////////////////////////////////////////////////////////////////////////////
4742 .chapter "The Exim run time configuration file" "CHAPconf" &&&
4743 "The runtime configuration file"
4745 .cindex "run time configuration"
4746 .cindex "configuration file" "general description"
4747 .cindex "CONFIGURE_FILE"
4748 .cindex "configuration file" "errors in"
4749 .cindex "error" "in configuration file"
4750 .cindex "return code" "for bad configuration"
4751 Exim uses a single run time configuration file that is read whenever an Exim
4752 binary is executed. Note that in normal operation, this happens frequently,
4753 because Exim is designed to operate in a distributed manner, without central
4756 If a syntax error is detected while reading the configuration file, Exim
4757 writes a message on the standard error, and exits with a non-zero return code.
4758 The message is also written to the panic log. &*Note*&: Only simple syntax
4759 errors can be detected at this time. The values of any expanded options are
4760 not checked until the expansion happens, even when the expansion does not
4761 actually alter the string.
4763 The name of the configuration file is compiled into the binary for security
4764 reasons, and is specified by the CONFIGURE_FILE compilation option. In
4765 most configurations, this specifies a single file. However, it is permitted to
4766 give a colon-separated list of file names, in which case Exim uses the first
4767 existing file in the list.
4770 .cindex "EXIM_GROUP"
4771 .cindex "CONFIGURE_OWNER"
4772 .cindex "CONFIGURE_GROUP"
4773 .cindex "configuration file" "ownership"
4774 .cindex "ownership" "configuration file"
4775 The run time configuration file must be owned by root or by the user that is
4776 specified at compile time by the CONFIGURE_OWNER option (if set). The
4777 configuration file must not be world-writeable, or group-writeable unless its
4778 group is the root group or the one specified at compile time by the
4779 CONFIGURE_GROUP option.
4781 &*Warning*&: In a conventional configuration, where the Exim binary is setuid
4782 to root, anybody who is able to edit the run time configuration file has an
4783 easy way to run commands as root. If you specify a user or group in the
4784 CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users
4785 who are members of that group will trivially be able to obtain root privileges.
4787 Up to Exim version 4.72, the run time configuration file was also permitted to
4788 be writeable by the Exim user and/or group. That has been changed in Exim 4.73
4789 since it offered a simple privilege escalation for any attacker who managed to
4790 compromise the Exim user account.
4792 A default configuration file, which will work correctly in simple situations,
4793 is provided in the file &_src/configure.default_&. If CONFIGURE_FILE
4794 defines just one file name, the installation process copies the default
4795 configuration to a new file of that name if it did not previously exist. If
4796 CONFIGURE_FILE is a list, no default is automatically installed. Chapter
4797 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default
4802 .section "Using a different configuration file" "SECID40"
4803 .cindex "configuration file" "alternate"
4804 A one-off alternate configuration can be specified by the &%-C%& command line
4805 option, which may specify a single file or a list of files. However, when
4806 &%-C%& is used, Exim gives up its root privilege, unless called by root (or
4807 unless the argument for &%-C%& is identical to the built-in value from
4808 CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller
4809 is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%&
4810 is useful mainly for checking the syntax of configuration files before
4811 installing them. No owner or group checks are done on a configuration file
4812 specified by &%-C%&, if root privilege has been dropped.
4814 Even the Exim user is not trusted to specify an arbitrary configuration file
4815 with the &%-C%& option to be used with root privileges, unless that file is
4816 listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of
4817 testing a configuration using &%-C%& right through message reception and
4818 delivery, even if the caller is root. The reception works, but by that time,
4819 Exim is running as the Exim user, so when it re-execs to regain privilege for
4820 the delivery, the use of &%-C%& causes privilege to be lost. However, root
4821 can test reception and delivery using two separate commands (one to put a
4822 message on the queue, using &%-odq%&, and another to do the delivery, using
4825 If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a
4826 prefix string with which any file named in a &%-C%& command line option must
4827 start. In addition, the file name must not contain the sequence &"&`/../`&"&.
4828 There is no default setting for ALT_CONFIG_PREFIX; when it is unset, any file
4829 name can be used with &%-C%&.
4831 One-off changes to a configuration can be specified by the &%-D%& command line
4832 option, which defines and overrides values for macros used inside the
4833 configuration file. However, like &%-C%&, the use of this option by a
4834 non-privileged user causes Exim to discard its root privilege.
4835 If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is
4836 completely disabled, and its use causes an immediate error exit.
4838 The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder
4839 to declare certain macro names trusted, such that root privilege will not
4840 necessarily be discarded.
4841 WHITELIST_D_MACROS defines a colon-separated list of macros which are
4842 considered safe and, if &%-D%& only supplies macros from this list, and the
4843 values are acceptable, then Exim will not give up root privilege if the caller
4844 is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a
4845 transition mechanism and is expected to be removed in the future. Acceptable
4846 values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`&
4848 Some sites may wish to use the same Exim binary on different machines that
4849 share a file system, but to use different configuration files on each machine.
4850 If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first
4851 looks for a file whose name is the configuration file name followed by a dot
4852 and the machine's node name, as obtained from the &[uname()]& function. If this
4853 file does not exist, the standard name is tried. This processing occurs for
4854 each file name in the list given by CONFIGURE_FILE or &%-C%&.
4856 In some esoteric situations different versions of Exim may be run under
4857 different effective uids and the CONFIGURE_FILE_USE_EUID is defined to
4858 help with this. See the comments in &_src/EDITME_& for details.
4862 .section "Configuration file format" "SECTconffilfor"
4863 .cindex "configuration file" "format of"
4864 .cindex "format" "configuration file"
4865 Exim's configuration file is divided into a number of different parts. General
4866 option settings must always appear at the start of the file. The other parts
4867 are all optional, and may appear in any order. Each part other than the first
4868 is introduced by the word &"begin"& followed by at least one literal
4869 space, and the name of the part. The optional parts are:
4872 &'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter
4875 .cindex "AUTH" "configuration"
4876 &'authenticators'&: Configuration settings for the authenticator drivers. These
4877 are concerned with the SMTP AUTH command (see chapter &<<CHAPSMTPAUTH>>&).
4879 &'routers'&: Configuration settings for the router drivers. Routers process
4880 addresses and determine how the message is to be delivered (see chapters
4881 &<<CHAProutergeneric>>&&--&<<CHAPredirect>>&).
4883 &'transports'&: Configuration settings for the transport drivers. Transports
4884 define mechanisms for copying messages to destinations (see chapters
4885 &<<CHAPtransportgeneric>>&&--&<<CHAPsmtptrans>>&).
4887 &'retry'&: Retry rules, for use when a message cannot be delivered immediately.
4888 If there is no retry section, or if it is empty (that is, no retry rules are
4889 defined), Exim will not retry deliveries. In this situation, temporary errors
4890 are treated the same as permanent errors. Retry rules are discussed in chapter
4893 &'rewrite'&: Global address rewriting rules, for use when a message arrives and
4894 when new addresses are generated during delivery. Rewriting is discussed in
4895 chapter &<<CHAPrewrite>>&.
4897 &'local_scan'&: Private options for the &[local_scan()]& function. If you
4898 want to use this feature, you must set
4900 LOCAL_SCAN_HAS_OPTIONS=yes
4902 in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]&
4903 facility are given in chapter &<<CHAPlocalscan>>&.
4906 .cindex "configuration file" "leading white space in"
4907 .cindex "configuration file" "trailing white space in"
4908 .cindex "white space" "in configuration file"
4909 Leading and trailing white space in configuration lines is always ignored.
4911 Blank lines in the file, and lines starting with a # character (ignoring
4912 leading white space) are treated as comments and are ignored. &*Note*&: A
4913 # character other than at the beginning of a line is not treated specially,
4914 and does not introduce a comment.
4916 Any non-comment line can be continued by ending it with a backslash. Note that
4917 the general rule for white space means that trailing white space after the
4918 backslash and leading white space at the start of continuation
4919 lines is ignored. Comment lines beginning with # (but not empty lines) may
4920 appear in the middle of a sequence of continuation lines.
4922 A convenient way to create a configuration file is to start from the
4923 default, which is supplied in &_src/configure.default_&, and add, delete, or
4924 change settings as required.
4926 The ACLs, retry rules, and rewriting rules have their own syntax which is
4927 described in chapters &<<CHAPACL>>&, &<<CHAPretry>>&, and &<<CHAPrewrite>>&,
4928 respectively. The other parts of the configuration file have some syntactic
4929 items in common, and these are described below, from section &<<SECTcos>>&
4930 onwards. Before that, the inclusion, macro, and conditional facilities are
4935 .section "File inclusions in the configuration file" "SECID41"
4936 .cindex "inclusions in configuration file"
4937 .cindex "configuration file" "including other files"
4938 .cindex "&`.include`& in configuration file"
4939 .cindex "&`.include_if_exists`& in configuration file"
4940 You can include other files inside Exim's run time configuration file by
4943 &`.include`& <&'file name'&>
4944 &`.include_if_exists`& <&'file name'&>
4946 on a line by itself. Double quotes round the file name are optional. If you use
4947 the first form, a configuration error occurs if the file does not exist; the
4948 second form does nothing for non-existent files.
4949 The first form allows a relative name. It is resolved relative to
4950 the directory of the including file. For the second form an absolute file
4953 Includes may be nested to any depth, but remember that Exim reads its
4954 configuration file often, so it is a good idea to keep them to a minimum.
4955 If you change the contents of an included file, you must HUP the daemon,
4956 because an included file is read only when the configuration itself is read.
4958 The processing of inclusions happens early, at a physical line level, so, like
4959 comment lines, an inclusion can be used in the middle of an option setting,
4962 hosts_lookup = a.b.c \
4965 Include processing happens after macro processing (see below). Its effect is to
4966 process the lines of the included file as if they occurred inline where the
4971 .section "Macros in the configuration file" "SECTmacrodefs"
4972 .cindex "macro" "description of"
4973 .cindex "configuration file" "macros"
4974 If a line in the main part of the configuration (that is, before the first
4975 &"begin"& line) begins with an upper case letter, it is taken as a macro
4976 definition, and must be of the form
4978 <&'name'&> = <&'rest of line'&>
4980 The name must consist of letters, digits, and underscores, and need not all be
4981 in upper case, though that is recommended. The rest of the line, including any
4982 continuations, is the replacement text, and has leading and trailing white
4983 space removed. Quotes are not removed. The replacement text can never end with
4984 a backslash character, but this doesn't seem to be a serious limitation.
4986 Macros may also be defined between router, transport, authenticator, or ACL
4987 definitions. They may not, however, be defined within an individual driver or
4988 ACL, or in the &%local_scan%&, retry, or rewrite sections of the configuration.
4990 .section "Macro substitution" "SECID42"
4991 Once a macro is defined, all subsequent lines in the file (and any included
4992 files) are scanned for the macro name; if there are several macros, the line is
4993 scanned for each in turn, in the order in which the macros are defined. The
4994 replacement text is not re-scanned for the current macro, though it is scanned
4995 for subsequently defined macros. For this reason, a macro name may not contain
4996 the name of a previously defined macro as a substring. You could, for example,
4999 &`ABCD_XYZ = `&<&'something'&>
5000 &`ABCD = `&<&'something else'&>
5002 but putting the definitions in the opposite order would provoke a configuration
5003 error. Macro expansion is applied to individual physical lines from the file,
5004 before checking for line continuation or file inclusion (see above). If a line
5005 consists solely of a macro name, and the expansion of the macro is empty, the
5006 line is ignored. A macro at the start of a line may turn the line into a
5007 comment line or a &`.include`& line.
5010 .section "Redefining macros" "SECID43"
5011 Once defined, the value of a macro can be redefined later in the configuration
5012 (or in an included file). Redefinition is specified by using &'=='& instead of
5017 MAC == updated value
5019 Redefinition does not alter the order in which the macros are applied to the
5020 subsequent lines of the configuration file. It is still the same order in which
5021 the macros were originally defined. All that changes is the macro's value.
5022 Redefinition makes it possible to accumulate values. For example:
5026 MAC == MAC and something added
5028 This can be helpful in situations where the configuration file is built
5029 from a number of other files.
5031 .section "Overriding macro values" "SECID44"
5032 The values set for macros in the configuration file can be overridden by the
5033 &%-D%& command line option, but Exim gives up its root privilege when &%-D%& is
5034 used, unless called by root or the Exim user. A definition on the command line
5035 using the &%-D%& option causes all definitions and redefinitions within the
5040 .section "Example of macro usage" "SECID45"
5041 As an example of macro usage, consider a configuration where aliases are looked
5042 up in a MySQL database. It helps to keep the file less cluttered if long
5043 strings such as SQL statements are defined separately as macros, for example:
5045 ALIAS_QUERY = select mailbox from user where \
5046 login='${quote_mysql:$local_part}';
5048 This can then be used in a &(redirect)& router setting like this:
5050 data = ${lookup mysql{ALIAS_QUERY}}
5052 In earlier versions of Exim macros were sometimes used for domain, host, or
5053 address lists. In Exim 4 these are handled better by named lists &-- see
5054 section &<<SECTnamedlists>>&.
5057 .section "Builtin macros" "SECTbuiltinmacros"
5058 Exim defines some macros depending on facilities available, which may
5059 differ due to build-time definitions and from one release to another.
5060 All of these macros start with an underscore.
5061 They can be used to conditionally include parts of a configuration
5064 The following classes of macros are defined:
5066 &` _HAVE_* `& build-time defines
5067 &` _DRIVER_ROUTER_* `& router drivers
5068 &` _DRIVER_TRANSPORT_* `& transport drivers
5069 &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers
5070 &` _OPT_MAIN_* `& main config options
5071 &` _OPT_ROUTERS_* `& generic router options
5072 &` _OPT_TRANSPORTS_* `& generic transport options
5073 &` _OPT_AUTHENTICATORS_* `& generic authenticator options
5074 &` _OPT_ROUTER_*_* `& private router options
5075 &` _OPT_TRANSPORT_*_* `& private transport options
5076 &` _OPT_AUTHENTICATOR_*_* `& private authenticator options
5079 Use an &"exim -bP macros"& command to get the list of macros.
5082 .section "Conditional skips in the configuration file" "SECID46"
5083 .cindex "configuration file" "conditional skips"
5084 .cindex "&`.ifdef`&"
5085 You can use the directives &`.ifdef`&, &`.ifndef`&, &`.elifdef`&,
5086 &`.elifndef`&, &`.else`&, and &`.endif`& to dynamically include or exclude
5087 portions of the configuration file. The processing happens whenever the file is
5088 read (that is, when an Exim binary starts to run).
5090 The implementation is very simple. Instances of the first four directives must
5091 be followed by text that includes the names of one or macros. The condition
5092 that is tested is whether or not any macro substitution has taken place in the
5096 message_size_limit = 50M
5098 message_size_limit = 100M
5101 sets a message size limit of 50M if the macro &`AAA`& is defined
5102 (or &`A`& or &`AA`&), and 100M
5103 otherwise. If there is more than one macro named on the line, the condition
5104 is true if any of them are defined. That is, it is an &"or"& condition. To
5105 obtain an &"and"& condition, you need to use nested &`.ifdef`&s.
5107 Although you can use a macro expansion to generate one of these directives,
5108 it is not very useful, because the condition &"there was a macro substitution
5109 in this line"& will always be true.
5111 Text following &`.else`& and &`.endif`& is ignored, and can be used as comment
5112 to clarify complicated nestings.
5116 .section "Common option syntax" "SECTcos"
5117 .cindex "common option syntax"
5118 .cindex "syntax of common options"
5119 .cindex "configuration file" "common option syntax"
5120 For the main set of options, driver options, and &[local_scan()]& options,
5121 each setting is on a line by itself, and starts with a name consisting of
5122 lower-case letters and underscores. Many options require a data value, and in
5123 these cases the name must be followed by an equals sign (with optional white
5124 space) and then the value. For example:
5126 qualify_domain = mydomain.example.com
5128 .cindex "hiding configuration option values"
5129 .cindex "configuration options" "hiding value of"
5130 .cindex "options" "hiding value of"
5131 Some option settings may contain sensitive data, for example, passwords for
5132 accessing databases. To stop non-admin users from using the &%-bP%& command
5133 line option to read these values, you can precede the option settings with the
5134 word &"hide"&. For example:
5136 hide mysql_servers = localhost/users/admin/secret-password
5138 For non-admin users, such options are displayed like this:
5140 mysql_servers = <value not displayable>
5142 If &"hide"& is used on a driver option, it hides the value of that option on
5143 all instances of the same driver.
5145 The following sections describe the syntax used for the different data types
5146 that are found in option settings.
5149 .section "Boolean options" "SECID47"
5150 .cindex "format" "boolean"
5151 .cindex "boolean configuration values"
5152 .oindex "&%no_%&&'xxx'&"
5153 .oindex "&%not_%&&'xxx'&"
5154 Options whose type is given as boolean are on/off switches. There are two
5155 different ways of specifying such options: with and without a data value. If
5156 the option name is specified on its own without data, the switch is turned on;
5157 if it is preceded by &"no_"& or &"not_"& the switch is turned off. However,
5158 boolean options may be followed by an equals sign and one of the words
5159 &"true"&, &"false"&, &"yes"&, or &"no"&, as an alternative syntax. For example,
5160 the following two settings have exactly the same effect:
5165 The following two lines also have the same (opposite) effect:
5170 You can use whichever syntax you prefer.
5175 .section "Integer values" "SECID48"
5176 .cindex "integer configuration values"
5177 .cindex "format" "integer"
5178 If an option's type is given as &"integer"&, the value can be given in decimal,
5179 hexadecimal, or octal. If it starts with a digit greater than zero, a decimal
5180 number is assumed. Otherwise, it is treated as an octal number unless it starts
5181 with the characters &"0x"&, in which case the remainder is interpreted as a
5184 If an integer value is followed by the letter K, it is multiplied by 1024; if
5185 it is followed by the letter M, it is multiplied by 1024x1024;
5186 if by the letter G, 1024x1024x1024.
5188 of integer option settings are output, values which are an exact multiple of
5189 1024 or 1024x1024 are sometimes, but not always, printed using the letters K
5190 and M. The printing style is independent of the actual input format that was
5194 .section "Octal integer values" "SECID49"
5195 .cindex "integer format"
5196 .cindex "format" "octal integer"
5197 If an option's type is given as &"octal integer"&, its value is always
5198 interpreted as an octal number, whether or not it starts with the digit zero.
5199 Such options are always output in octal.
5202 .section "Fixed point numbers" "SECID50"
5203 .cindex "fixed point configuration values"
5204 .cindex "format" "fixed point"
5205 If an option's type is given as &"fixed-point"&, its value must be a decimal
5206 integer, optionally followed by a decimal point and up to three further digits.
5210 .section "Time intervals" "SECTtimeformat"
5211 .cindex "time interval" "specifying in configuration"
5212 .cindex "format" "time interval"
5213 A time interval is specified as a sequence of numbers, each followed by one of
5214 the following letters, with no intervening white space:
5224 For example, &"3h50m"& specifies 3 hours and 50 minutes. The values of time
5225 intervals are output in the same format. Exim does not restrict the values; it
5226 is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&.
5230 .section "String values" "SECTstrings"
5231 .cindex "string" "format of configuration values"
5232 .cindex "format" "string"
5233 If an option's type is specified as &"string"&, the value can be specified with
5234 or without double-quotes. If it does not start with a double-quote, the value
5235 consists of the remainder of the line plus any continuation lines, starting at
5236 the first character after any leading white space, with trailing white space
5237 removed, and with no interpretation of the characters in the string. Because
5238 Exim removes comment lines (those beginning with #) at an early stage, they can
5239 appear in the middle of a multi-line string. The following two settings are
5240 therefore equivalent:
5242 trusted_users = uucp:mail
5243 trusted_users = uucp:\
5244 # This comment line is ignored
5247 .cindex "string" "quoted"
5248 .cindex "escape characters in quoted strings"
5249 If a string does start with a double-quote, it must end with a closing
5250 double-quote, and any backslash characters other than those used for line
5251 continuation are interpreted as escape characters, as follows:
5254 .irow &`\\`& "single backslash"
5255 .irow &`\n`& "newline"
5256 .irow &`\r`& "carriage return"
5258 .irow "&`\`&<&'octal digits'&>" "up to 3 octal digits specify one character"
5259 .irow "&`\x`&<&'hex digits'&>" "up to 2 hexadecimal digits specify one &&&
5263 If a backslash is followed by some other character, including a double-quote
5264 character, that character replaces the pair.
5266 Quoting is necessary only if you want to make use of the backslash escapes to
5267 insert special characters, or if you need to specify a value with leading or
5268 trailing spaces. These cases are rare, so quoting is almost never needed in
5269 current versions of Exim. In versions of Exim before 3.14, quoting was required
5270 in order to continue lines, so you may come across older configuration files
5271 and examples that apparently quote unnecessarily.
5274 .section "Expanded strings" "SECID51"
5275 .cindex "expansion" "definition of"
5276 Some strings in the configuration file are subjected to &'string expansion'&,
5277 by which means various parts of the string may be changed according to the
5278 circumstances (see chapter &<<CHAPexpand>>&). The input syntax for such strings
5279 is as just described; in particular, the handling of backslashes in quoted
5280 strings is done as part of the input process, before expansion takes place.
5281 However, backslash is also an escape character for the expander, so any
5282 backslashes that are required for that reason must be doubled if they are
5283 within a quoted configuration string.
5286 .section "User and group names" "SECID52"
5287 .cindex "user name" "format of"
5288 .cindex "format" "user name"
5289 .cindex "groups" "name format"
5290 .cindex "format" "group name"
5291 User and group names are specified as strings, using the syntax described
5292 above, but the strings are interpreted specially. A user or group name must
5293 either consist entirely of digits, or be a name that can be looked up using the
5294 &[getpwnam()]& or &[getgrnam()]& function, as appropriate.
5297 .section "List construction" "SECTlistconstruct"
5298 .cindex "list" "syntax of in configuration"
5299 .cindex "format" "list item in configuration"
5300 .cindex "string" "list, definition of"
5301 The data for some configuration options is a list of items, with colon as the
5302 default separator. Many of these options are shown with type &"string list"& in
5303 the descriptions later in this document. Others are listed as &"domain list"&,
5304 &"host list"&, &"address list"&, or &"local part list"&. Syntactically, they
5305 are all the same; however, those other than &"string list"& are subject to
5306 particular kinds of interpretation, as described in chapter
5307 &<<CHAPdomhosaddlists>>&.
5309 In all these cases, the entire list is treated as a single string as far as the
5310 input syntax is concerned. The &%trusted_users%& setting in section
5311 &<<SECTstrings>>& above is an example. If a colon is actually needed in an item
5312 in a list, it must be entered as two colons. Leading and trailing white space
5313 on each item in a list is ignored. This makes it possible to include items that
5314 start with a colon, and in particular, certain forms of IPv6 address. For
5317 local_interfaces = 127.0.0.1 : ::::1
5319 contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
5321 &*Note*&: Although leading and trailing white space is ignored in individual
5322 list items, it is not ignored when parsing the list. The space after the first
5323 colon in the example above is necessary. If it were not there, the list would
5324 be interpreted as the two items 127.0.0.1:: and 1.
5326 .section "Changing list separators" "SECTlistsepchange"
5327 .cindex "list separator" "changing"
5328 .cindex "IPv6" "addresses in lists"
5329 Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was
5330 introduced to allow the separator character to be changed. If a list begins
5331 with a left angle bracket, followed by any punctuation character, that
5332 character is used instead of colon as the list separator. For example, the list
5333 above can be rewritten to use a semicolon separator like this:
5335 local_interfaces = <; 127.0.0.1 ; ::1
5337 This facility applies to all lists, with the exception of the list in
5338 &%log_file_path%&. It is recommended that the use of non-colon separators be
5339 confined to circumstances where they really are needed.
5341 .cindex "list separator" "newline as"
5342 .cindex "newline" "as list separator"
5343 It is also possible to use newline and other control characters (those with
5344 code values less than 32, plus DEL) as separators in lists. Such separators
5345 must be provided literally at the time the list is processed. For options that
5346 are string-expanded, you can write the separator using a normal escape
5347 sequence. This will be processed by the expander before the string is
5348 interpreted as a list. For example, if a newline-separated list of domains is
5349 generated by a lookup, you can process it directly by a line such as this:
5351 domains = <\n ${lookup mysql{.....}}
5353 This avoids having to change the list separator in such data. You are unlikely
5354 to want to use a control character as a separator in an option that is not
5355 expanded, because the value is literal text. However, it can be done by giving
5356 the value in quotes. For example:
5358 local_interfaces = "<\n 127.0.0.1 \n ::1"
5360 Unlike printing character separators, which can be included in list items by
5361 doubling, it is not possible to include a control character as data when it is
5362 set as the separator. Two such characters in succession are interpreted as
5363 enclosing an empty list item.
5367 .section "Empty items in lists" "SECTempitelis"
5368 .cindex "list" "empty item in"
5369 An empty item at the end of a list is always ignored. In other words, trailing
5370 separator characters are ignored. Thus, the list in
5372 senders = user@domain :
5374 contains only a single item. If you want to include an empty string as one item
5375 in a list, it must not be the last item. For example, this list contains three
5376 items, the second of which is empty:
5378 senders = user1@domain : : user2@domain
5380 &*Note*&: There must be white space between the two colons, as otherwise they
5381 are interpreted as representing a single colon data character (and the list
5382 would then contain just one item). If you want to specify a list that contains
5383 just one, empty item, you can do it as in this example:
5387 In this case, the first item is empty, and the second is discarded because it
5388 is at the end of the list.
5393 .section "Format of driver configurations" "SECTfordricon"
5394 .cindex "drivers" "configuration format"
5395 There are separate parts in the configuration for defining routers, transports,
5396 and authenticators. In each part, you are defining a number of driver
5397 instances, each with its own set of options. Each driver instance is defined by
5398 a sequence of lines like this:
5400 <&'instance name'&>:
5405 In the following example, the instance name is &(localuser)&, and it is
5406 followed by three options settings:
5411 transport = local_delivery
5413 For each driver instance, you specify which Exim code module it uses &-- by the
5414 setting of the &%driver%& option &-- and (optionally) some configuration
5415 settings. For example, in the case of transports, if you want a transport to
5416 deliver with SMTP you would use the &(smtp)& driver; if you want to deliver to
5417 a local file you would use the &(appendfile)& driver. Each of the drivers is
5418 described in detail in its own separate chapter later in this manual.
5420 You can have several routers, transports, or authenticators that are based on
5421 the same underlying driver (each must have a different instance name).
5423 The order in which routers are defined is important, because addresses are
5424 passed to individual routers one by one, in order. The order in which
5425 transports are defined does not matter at all. The order in which
5426 authenticators are defined is used only when Exim, as a client, is searching
5427 them to find one that matches an authentication mechanism offered by the
5430 .cindex "generic options"
5431 .cindex "options" "generic &-- definition of"
5432 Within a driver instance definition, there are two kinds of option: &'generic'&
5433 and &'private'&. The generic options are those that apply to all drivers of the
5434 same type (that is, all routers, all transports or all authenticators). The
5435 &%driver%& option is a generic option that must appear in every definition.
5436 .cindex "private options"
5437 The private options are special for each driver, and none need appear, because
5438 they all have default values.
5440 The options may appear in any order, except that the &%driver%& option must
5441 precede any private options, since these depend on the particular driver. For
5442 this reason, it is recommended that &%driver%& always be the first option.
5444 Driver instance names, which are used for reference in log entries and
5445 elsewhere, can be any sequence of letters, digits, and underscores (starting
5446 with a letter) and must be unique among drivers of the same type. A router and
5447 a transport (for example) can each have the same name, but no two router
5448 instances can have the same name. The name of a driver instance should not be
5449 confused with the name of the underlying driver module. For example, the
5450 configuration lines:
5455 create an instance of the &(smtp)& transport driver whose name is
5456 &(remote_smtp)&. The same driver code can be used more than once, with
5457 different instance names and different option settings each time. A second
5458 instance of the &(smtp)& transport, with different options, might be defined
5464 command_timeout = 10s
5466 The names &(remote_smtp)& and &(special_smtp)& would be used to reference
5467 these transport instances from routers, and these names would appear in log
5470 Comment lines may be present in the middle of driver specifications. The full
5471 list of option settings for any particular driver instance, including all the
5472 defaulted values, can be extracted by making use of the &%-bP%& command line
5480 . ////////////////////////////////////////////////////////////////////////////
5481 . ////////////////////////////////////////////////////////////////////////////
5483 .chapter "The default configuration file" "CHAPdefconfil"
5484 .scindex IIDconfiwal "configuration file" "default &""walk through""&"
5485 .cindex "default" "configuration file &""walk through""&"
5486 The default configuration file supplied with Exim as &_src/configure.default_&
5487 is sufficient for a host with simple mail requirements. As an introduction to
5488 the way Exim is configured, this chapter &"walks through"& the default
5489 configuration, giving brief explanations of the settings. Detailed descriptions
5490 of the options are given in subsequent chapters. The default configuration file
5491 itself contains extensive comments about ways you might want to modify the
5492 initial settings. However, note that there are many options that are not
5493 mentioned at all in the default configuration.
5497 .section "Main configuration settings" "SECTdefconfmain"
5498 The main (global) configuration option settings must always come first in the
5499 file. The first thing you'll see in the file, after some initial comments, is
5502 # primary_hostname =
5504 This is a commented-out setting of the &%primary_hostname%& option. Exim needs
5505 to know the official, fully qualified name of your host, and this is where you
5506 can specify it. However, in most cases you do not need to set this option. When
5507 it is unset, Exim uses the &[uname()]& system function to obtain the host name.
5509 The first three non-comment configuration lines are as follows:
5511 domainlist local_domains = @
5512 domainlist relay_to_domains =
5513 hostlist relay_from_hosts = 127.0.0.1
5515 These are not, in fact, option settings. They are definitions of two named
5516 domain lists and one named host list. Exim allows you to give names to lists of
5517 domains, hosts, and email addresses, in order to make it easier to manage the
5518 configuration file (see section &<<SECTnamedlists>>&).
5520 The first line defines a domain list called &'local_domains'&; this is used
5521 later in the configuration to identify domains that are to be delivered
5524 .cindex "@ in a domain list"
5525 There is just one item in this list, the string &"@"&. This is a special form
5526 of entry which means &"the name of the local host"&. Thus, if the local host is
5527 called &'a.host.example'&, mail to &'any.user@a.host.example'& is expected to
5528 be delivered locally. Because the local host's name is referenced indirectly,
5529 the same configuration file can be used on different hosts.
5531 The second line defines a domain list called &'relay_to_domains'&, but the
5532 list itself is empty. Later in the configuration we will come to the part that
5533 controls mail relaying through the local host; it allows relaying to any
5534 domains in this list. By default, therefore, no relaying on the basis of a mail
5535 domain is permitted.
5537 The third line defines a host list called &'relay_from_hosts'&. This list is
5538 used later in the configuration to permit relaying from any host or IP address
5539 that matches the list. The default contains just the IP address of the IPv4
5540 loopback interface, which means that processes on the local host are able to
5541 submit mail for relaying by sending it over TCP/IP to that interface. No other
5542 hosts are permitted to submit messages for relaying.
5544 Just to be sure there's no misunderstanding: at this point in the configuration
5545 we aren't actually setting up any controls. We are just defining some domains
5546 and hosts that will be used in the controls that are specified later.
5548 The next two configuration lines are genuine option settings:
5550 acl_smtp_rcpt = acl_check_rcpt
5551 acl_smtp_data = acl_check_data
5553 These options specify &'Access Control Lists'& (ACLs) that are to be used
5554 during an incoming SMTP session for every recipient of a message (every RCPT
5555 command), and after the contents of the message have been received,
5556 respectively. The names of the lists are &'acl_check_rcpt'& and
5557 &'acl_check_data'&, and we will come to their definitions below, in the ACL
5558 section of the configuration. The RCPT ACL controls which recipients are
5559 accepted for an incoming message &-- if a configuration does not provide an ACL
5560 to check recipients, no SMTP mail can be accepted. The DATA ACL allows the
5561 contents of a message to be checked.
5563 Two commented-out option settings are next:
5565 # av_scanner = clamd:/tmp/clamd
5566 # spamd_address = 127.0.0.1 783
5568 These are example settings that can be used when Exim is compiled with the
5569 content-scanning extension. The first specifies the interface to the virus
5570 scanner, and the second specifies the interface to SpamAssassin. Further
5571 details are given in chapter &<<CHAPexiscan>>&.
5573 Three more commented-out option settings follow:
5575 # tls_advertise_hosts = *
5576 # tls_certificate = /etc/ssl/exim.crt
5577 # tls_privatekey = /etc/ssl/exim.pem
5579 These are example settings that can be used when Exim is compiled with
5580 support for TLS (aka SSL) as described in section &<<SECTinctlsssl>>&. The
5581 first one specifies the list of clients that are allowed to use TLS when
5582 connecting to this server; in this case the wildcard means all clients. The
5583 other options specify where Exim should find its TLS certificate and private
5584 key, which together prove the server's identity to any clients that connect.
5585 More details are given in chapter &<<CHAPTLS>>&.
5587 Another two commented-out option settings follow:
5589 # daemon_smtp_ports = 25 : 465 : 587
5590 # tls_on_connect_ports = 465
5592 .cindex "port" "465 and 587"
5593 .cindex "port" "for message submission"
5594 .cindex "message" "submission, ports for"
5595 .cindex "submissions protocol"
5596 .cindex "smtps protocol"
5597 .cindex "ssmtp protocol"
5598 .cindex "SMTP" "submissions protocol"
5599 .cindex "SMTP" "ssmtp protocol"
5600 .cindex "SMTP" "smtps protocol"
5601 These options provide better support for roaming users who wish to use this
5602 server for message submission. They are not much use unless you have turned on
5603 TLS (as described in the previous paragraph) and authentication (about which
5604 more in section &<<SECTdefconfauth>>&).
5605 Mail submission from mail clients (MUAs) should be separate from inbound mail
5606 to your domain (MX delivery) for various good reasons (eg, ability to impose
5607 much saner TLS protocol and ciphersuite requirements without unintended
5609 RFC 6409 (previously 4409) specifies use of port 587 for SMTP Submission,
5610 which uses STARTTLS, so this is the &"submission"& port.
5611 RFC 8314 specifies use of port 465 as the &"submissions"& protocol,
5612 which should be used in preference to 587.
5613 You should also consider deploying SRV records to help clients find
5615 Older names for &"submissions"& are &"smtps"& and &"ssmtp"&.
5617 Two more commented-out options settings follow:
5620 # qualify_recipient =
5622 The first of these specifies a domain that Exim uses when it constructs a
5623 complete email address from a local login name. This is often needed when Exim
5624 receives a message from a local process. If you do not set &%qualify_domain%&,
5625 the value of &%primary_hostname%& is used. If you set both of these options,
5626 you can have different qualification domains for sender and recipient
5627 addresses. If you set only the first one, its value is used in both cases.
5629 .cindex "domain literal" "recognizing format"
5630 The following line must be uncommented if you want Exim to recognize
5631 addresses of the form &'user@[10.11.12.13]'& that is, with a &"domain literal"&
5632 (an IP address within square brackets) instead of a named domain.
5634 # allow_domain_literals
5636 The RFCs still require this form, but many people think that in the modern
5637 Internet it makes little sense to permit mail to be sent to specific hosts by
5638 quoting their IP addresses. This ancient format has been used by people who
5639 try to abuse hosts by using them for unwanted relaying. However, some
5640 people believe there are circumstances (for example, messages addressed to
5641 &'postmaster'&) where domain literals are still useful.
5643 The next configuration line is a kind of trigger guard:
5647 It specifies that no delivery must ever be run as the root user. The normal
5648 convention is to set up &'root'& as an alias for the system administrator. This
5649 setting is a guard against slips in the configuration.
5650 The list of users specified by &%never_users%& is not, however, the complete
5651 list; the build-time configuration in &_Local/Makefile_& has an option called
5652 FIXED_NEVER_USERS specifying a list that cannot be overridden. The
5653 contents of &%never_users%& are added to this list. By default
5654 FIXED_NEVER_USERS also specifies root.
5656 When a remote host connects to Exim in order to send mail, the only information
5657 Exim has about the host's identity is its IP address. The next configuration
5662 specifies that Exim should do a reverse DNS lookup on all incoming connections,
5663 in order to get a host name. This improves the quality of the logging
5664 information, but if you feel it is too expensive, you can remove it entirely,
5665 or restrict the lookup to hosts on &"nearby"& networks.
5666 Note that it is not always possible to find a host name from an IP address,
5667 because not all DNS reverse zones are maintained, and sometimes DNS servers are
5670 The next two lines are concerned with &'ident'& callbacks, as defined by RFC
5671 1413 (hence their names):
5674 rfc1413_query_timeout = 0s
5676 These settings cause Exim to avoid ident callbacks for all incoming SMTP calls.
5677 Few hosts offer RFC1413 service these days; calls have to be
5678 terminated by a timeout and this needlessly delays the startup
5679 of an incoming SMTP connection.
5680 If you have hosts for which you trust RFC1413 and need this
5681 information, you can change this.
5683 This line enables an efficiency SMTP option. It is negotiated by clients
5684 and not expected to cause problems but can be disabled if needed.
5689 When Exim receives messages over SMTP connections, it expects all addresses to
5690 be fully qualified with a domain, as required by the SMTP definition. However,
5691 if you are running a server to which simple clients submit messages, you may
5692 find that they send unqualified addresses. The two commented-out options:
5694 # sender_unqualified_hosts =
5695 # recipient_unqualified_hosts =
5697 show how you can specify hosts that are permitted to send unqualified sender
5698 and recipient addresses, respectively.
5700 The &%log_selector%& option is used to increase the detail of logging
5703 log_selector = +smtp_protocol_error +smtp_syntax_error \
5704 +tls_certificate_verified
5707 The &%percent_hack_domains%& option is also commented out:
5709 # percent_hack_domains =
5711 It provides a list of domains for which the &"percent hack"& is to operate.
5712 This is an almost obsolete form of explicit email routing. If you do not know
5713 anything about it, you can safely ignore this topic.
5715 The next two settings in the main part of the default configuration are
5716 concerned with messages that have been &"frozen"& on Exim's queue. When a
5717 message is frozen, Exim no longer continues to try to deliver it. Freezing
5718 occurs when a bounce message encounters a permanent failure because the sender
5719 address of the original message that caused the bounce is invalid, so the
5720 bounce cannot be delivered. This is probably the most common case, but there
5721 are also other conditions that cause freezing, and frozen messages are not
5722 always bounce messages.
5724 ignore_bounce_errors_after = 2d
5725 timeout_frozen_after = 7d
5727 The first of these options specifies that failing bounce messages are to be
5728 discarded after 2 days on the queue. The second specifies that any frozen
5729 message (whether a bounce message or not) is to be timed out (and discarded)
5730 after a week. In this configuration, the first setting ensures that no failing
5731 bounce message ever lasts a week.
5733 Exim queues it's messages in a spool directory. If you expect to have
5734 large queues, you may consider using this option. It splits the spool
5735 directory into subdirectories to avoid file system degradation from
5736 many files in a single directory, resulting in better performance.
5737 Manual manipulation of queued messages becomes more complex (though fortunately
5740 # split_spool_directory = true
5743 In an ideal world everybody follows the standards. For non-ASCII
5744 messages RFC 2047 is a standard, allowing a maximum line length of 76
5745 characters. Exim adheres that standard and won't process messages which
5746 violate this standard. (Even ${rfc2047:...} expansions will fail.)
5747 In particular, the Exim maintainers have had multiple reports of
5748 problems from Russian administrators of issues until they disable this
5749 check, because of some popular, yet buggy, mail composition software.
5751 # check_rfc2047_length = false
5754 If you need to be strictly RFC compliant you may wish to disable the
5755 8BITMIME advertisement. Use this, if you exchange mails with systems
5756 that are not 8-bit clean.
5758 # accept_8bitmime = false
5761 Libraries you use may depend on specific environment settings. This
5762 imposes a security risk (e.g. PATH). There are two lists:
5763 &%keep_environment%& for the variables to import as they are, and
5764 &%add_environment%& for variables we want to set to a fixed value.
5765 Note that TZ is handled separately, by the $%timezone%$ runtime
5766 option and by the TIMEZONE_DEFAULT buildtime option.
5768 # keep_environment = ^LDAP
5769 # add_environment = PATH=/usr/bin::/bin
5773 .section "ACL configuration" "SECID54"
5774 .cindex "default" "ACLs"
5775 .cindex "&ACL;" "default configuration"
5776 In the default configuration, the ACL section follows the main configuration.
5777 It starts with the line
5781 and it contains the definitions of two ACLs, called &'acl_check_rcpt'& and
5782 &'acl_check_data'&, that were referenced in the settings of &%acl_smtp_rcpt%&
5783 and &%acl_smtp_data%& above.
5785 .cindex "RCPT" "ACL for"
5786 The first ACL is used for every RCPT command in an incoming SMTP message. Each
5787 RCPT command specifies one of the message's recipients. The ACL statements
5788 are considered in order, until the recipient address is either accepted or
5789 rejected. The RCPT command is then accepted or rejected, according to the
5790 result of the ACL processing.
5794 This line, consisting of a name terminated by a colon, marks the start of the
5799 This ACL statement accepts the recipient if the sending host matches the list.
5800 But what does that strange list mean? It doesn't actually contain any host
5801 names or IP addresses. The presence of the colon puts an empty item in the
5802 list; Exim matches this only if the incoming message did not come from a remote
5803 host, because in that case, the remote hostname is empty. The colon is
5804 important. Without it, the list itself is empty, and can never match anything.
5806 What this statement is doing is to accept unconditionally all recipients in
5807 messages that are submitted by SMTP from local processes using the standard
5808 input and output (that is, not using TCP/IP). A number of MUAs operate in this
5811 deny message = Restricted characters in address
5812 domains = +local_domains
5813 local_parts = ^[.] : ^.*[@%!/|]
5815 deny message = Restricted characters in address
5816 domains = !+local_domains
5817 local_parts = ^[./|] : ^.*[@%!] : ^.*/\\.\\./
5819 These statements are concerned with local parts that contain any of the
5820 characters &"@"&, &"%"&, &"!"&, &"/"&, &"|"&, or dots in unusual places.
5821 Although these characters are entirely legal in local parts (in the case of
5822 &"@"& and leading dots, only if correctly quoted), they do not commonly occur
5823 in Internet mail addresses.
5825 The first three have in the past been associated with explicitly routed
5826 addresses (percent is still sometimes used &-- see the &%percent_hack_domains%&
5827 option). Addresses containing these characters are regularly tried by spammers
5828 in an attempt to bypass relaying restrictions, and also by open relay testing
5829 programs. Unless you really need them it is safest to reject these characters
5830 at this early stage. This configuration is heavy-handed in rejecting these
5831 characters for all messages it accepts from remote hosts. This is a deliberate
5832 policy of being as safe as possible.
5834 The first rule above is stricter, and is applied to messages that are addressed
5835 to one of the local domains handled by this host. This is implemented by the
5836 first condition, which restricts it to domains that are listed in the
5837 &'local_domains'& domain list. The &"+"& character is used to indicate a
5838 reference to a named list. In this configuration, there is just one domain in
5839 &'local_domains'&, but in general there may be many.
5841 The second condition on the first statement uses two regular expressions to
5842 block local parts that begin with a dot or contain &"@"&, &"%"&, &"!"&, &"/"&,
5843 or &"|"&. If you have local accounts that include these characters, you will
5844 have to modify this rule.
5846 Empty components (two dots in a row) are not valid in RFC 2822, but Exim
5847 allows them because they have been encountered in practice. (Consider the
5848 common convention of local parts constructed as
5849 &"&'first-initial.second-initial.family-name'&"& when applied to someone like
5850 the author of Exim, who has no second initial.) However, a local part starting
5851 with a dot or containing &"/../"& can cause trouble if it is used as part of a
5852 file name (for example, for a mailing list). This is also true for local parts
5853 that contain slashes. A pipe symbol can also be troublesome if the local part
5854 is incorporated unthinkingly into a shell command line.
5856 The second rule above applies to all other domains, and is less strict. This
5857 allows your own users to send outgoing messages to sites that use slashes
5858 and vertical bars in their local parts. It blocks local parts that begin
5859 with a dot, slash, or vertical bar, but allows these characters within the
5860 local part. However, the sequence &"/../"& is barred. The use of &"@"&, &"%"&,
5861 and &"!"& is blocked, as before. The motivation here is to prevent your users
5862 (or your users' viruses) from mounting certain kinds of attack on remote sites.
5864 accept local_parts = postmaster
5865 domains = +local_domains
5867 This statement, which has two conditions, accepts an incoming address if the
5868 local part is &'postmaster'& and the domain is one of those listed in the
5869 &'local_domains'& domain list. The &"+"& character is used to indicate a
5870 reference to a named list. In this configuration, there is just one domain in
5871 &'local_domains'&, but in general there may be many.
5873 The presence of this statement means that mail to postmaster is never blocked
5874 by any of the subsequent tests. This can be helpful while sorting out problems
5875 in cases where the subsequent tests are incorrectly denying access.
5877 require verify = sender
5879 This statement requires the sender address to be verified before any subsequent
5880 ACL statement can be used. If verification fails, the incoming recipient
5881 address is refused. Verification consists of trying to route the address, to
5882 see if a bounce message could be delivered to it. In the case of remote
5883 addresses, basic verification checks only the domain, but &'callouts'& can be
5884 used for more verification if required. Section &<<SECTaddressverification>>&
5885 discusses the details of address verification.
5887 accept hosts = +relay_from_hosts
5888 control = submission
5890 This statement accepts the address if the message is coming from one of the
5891 hosts that are defined as being allowed to relay through this host. Recipient
5892 verification is omitted here, because in many cases the clients are dumb MUAs
5893 that do not cope well with SMTP error responses. For the same reason, the
5894 second line specifies &"submission mode"& for messages that are accepted. This
5895 is described in detail in section &<<SECTsubmodnon>>&; it causes Exim to fix
5896 messages that are deficient in some way, for example, because they lack a
5897 &'Date:'& header line. If you are actually relaying out from MTAs, you should
5898 probably add recipient verification here, and disable submission mode.
5900 accept authenticated = *
5901 control = submission
5903 This statement accepts the address if the client host has authenticated itself.
5904 Submission mode is again specified, on the grounds that such messages are most
5905 likely to come from MUAs. The default configuration does not define any
5906 authenticators, though it does include some nearly complete commented-out
5907 examples described in &<<SECTdefconfauth>>&. This means that no client can in
5908 fact authenticate until you complete the authenticator definitions.
5910 require message = relay not permitted
5911 domains = +local_domains : +relay_to_domains
5913 This statement rejects the address if its domain is neither a local domain nor
5914 one of the domains for which this host is a relay.
5916 require verify = recipient
5918 This statement requires the recipient address to be verified; if verification
5919 fails, the address is rejected.
5921 # deny message = rejected because $sender_host_address \
5922 # is in a black list at $dnslist_domain\n\
5924 # dnslists = black.list.example
5926 # warn dnslists = black.list.example
5927 # add_header = X-Warning: $sender_host_address is in \
5928 # a black list at $dnslist_domain
5929 # log_message = found in $dnslist_domain
5931 These commented-out lines are examples of how you could configure Exim to check
5932 sending hosts against a DNS black list. The first statement rejects messages
5933 from blacklisted hosts, whereas the second just inserts a warning header
5936 # require verify = csa
5938 This commented-out line is an example of how you could turn on client SMTP
5939 authorization (CSA) checking. Such checks do DNS lookups for special SRV
5944 The final statement in the first ACL unconditionally accepts any recipient
5945 address that has successfully passed all the previous tests.
5949 This line marks the start of the second ACL, and names it. Most of the contents
5950 of this ACL are commented out:
5953 # message = This message contains a virus \
5956 These lines are examples of how to arrange for messages to be scanned for
5957 viruses when Exim has been compiled with the content-scanning extension, and a
5958 suitable virus scanner is installed. If the message is found to contain a
5959 virus, it is rejected with the given custom error message.
5961 # warn spam = nobody
5962 # message = X-Spam_score: $spam_score\n\
5963 # X-Spam_score_int: $spam_score_int\n\
5964 # X-Spam_bar: $spam_bar\n\
5965 # X-Spam_report: $spam_report
5967 These lines are an example of how to arrange for messages to be scanned by
5968 SpamAssassin when Exim has been compiled with the content-scanning extension,
5969 and SpamAssassin has been installed. The SpamAssassin check is run with
5970 &`nobody`& as its user parameter, and the results are added to the message as a
5971 series of extra header line. In this case, the message is not rejected,
5972 whatever the spam score.
5976 This final line in the DATA ACL accepts the message unconditionally.
5979 .section "Router configuration" "SECID55"
5980 .cindex "default" "routers"
5981 .cindex "routers" "default"
5982 The router configuration comes next in the default configuration, introduced
5987 Routers are the modules in Exim that make decisions about where to send
5988 messages. An address is passed to each router in turn, until it is either
5989 accepted, or failed. This means that the order in which you define the routers
5990 matters. Each router is fully described in its own chapter later in this
5991 manual. Here we give only brief overviews.
5994 # driver = ipliteral
5995 # domains = !+local_domains
5996 # transport = remote_smtp
5998 .cindex "domain literal" "default router"
5999 This router is commented out because the majority of sites do not want to
6000 support domain literal addresses (those of the form &'user@[10.9.8.7]'&). If
6001 you uncomment this router, you also need to uncomment the setting of
6002 &%allow_domain_literals%& in the main part of the configuration.
6006 domains = ! +local_domains
6007 transport = remote_smtp
6008 ignore_target_hosts = 0.0.0.0 : 127.0.0.0/8
6011 The first uncommented router handles addresses that do not involve any local
6012 domains. This is specified by the line
6014 domains = ! +local_domains
6016 The &%domains%& option lists the domains to which this router applies, but the
6017 exclamation mark is a negation sign, so the router is used only for domains
6018 that are not in the domain list called &'local_domains'& (which was defined at
6019 the start of the configuration). The plus sign before &'local_domains'&
6020 indicates that it is referring to a named list. Addresses in other domains are
6021 passed on to the following routers.
6023 The name of the router driver is &(dnslookup)&,
6024 and is specified by the &%driver%& option. Do not be confused by the fact that
6025 the name of this router instance is the same as the name of the driver. The
6026 instance name is arbitrary, but the name set in the &%driver%& option must be
6027 one of the driver modules that is in the Exim binary.
6029 The &(dnslookup)& router routes addresses by looking up their domains in the
6030 DNS in order to obtain a list of hosts to which the address is routed. If the
6031 router succeeds, the address is queued for the &(remote_smtp)& transport, as
6032 specified by the &%transport%& option. If the router does not find the domain
6033 in the DNS, no further routers are tried because of the &%no_more%& setting, so
6034 the address fails and is bounced.
6036 The &%ignore_target_hosts%& option specifies a list of IP addresses that are to
6037 be entirely ignored. This option is present because a number of cases have been
6038 encountered where MX records in the DNS point to host names
6039 whose IP addresses are 0.0.0.0 or are in the 127 subnet (typically 127.0.0.1).
6040 Completely ignoring these IP addresses causes Exim to fail to route the
6041 email address, so it bounces. Otherwise, Exim would log a routing problem, and
6042 continue to try to deliver the message periodically until the address timed
6049 data = ${lookup{$local_part}lsearch{/etc/aliases}}
6051 file_transport = address_file
6052 pipe_transport = address_pipe
6054 Control reaches this and subsequent routers only for addresses in the local
6055 domains. This router checks to see whether the local part is defined as an
6056 alias in the &_/etc/aliases_& file, and if so, redirects it according to the
6057 data that it looks up from that file. If no data is found for the local part,
6058 the value of the &%data%& option is empty, causing the address to be passed to
6061 &_/etc/aliases_& is a conventional name for the system aliases file that is
6062 often used. That is why it is referenced by from the default configuration
6063 file. However, you can change this by setting SYSTEM_ALIASES_FILE in
6064 &_Local/Makefile_& before building Exim.
6069 # local_part_suffix = +* : -*
6070 # local_part_suffix_optional
6071 file = $home/.forward
6076 file_transport = address_file
6077 pipe_transport = address_pipe
6078 reply_transport = address_reply
6080 This is the most complicated router in the default configuration. It is another
6081 redirection router, but this time it is looking for forwarding data set up by
6082 individual users. The &%check_local_user%& setting specifies a check that the
6083 local part of the address is the login name of a local user. If it is not, the
6084 router is skipped. The two commented options that follow &%check_local_user%&,
6087 # local_part_suffix = +* : -*
6088 # local_part_suffix_optional
6090 .vindex "&$local_part_suffix$&"
6091 show how you can specify the recognition of local part suffixes. If the first
6092 is uncommented, a suffix beginning with either a plus or a minus sign, followed
6093 by any sequence of characters, is removed from the local part and placed in the
6094 variable &$local_part_suffix$&. The second suffix option specifies that the
6095 presence of a suffix in the local part is optional. When a suffix is present,
6096 the check for a local login uses the local part with the suffix removed.
6098 When a local user account is found, the file called &_.forward_& in the user's
6099 home directory is consulted. If it does not exist, or is empty, the router
6100 declines. Otherwise, the contents of &_.forward_& are interpreted as
6101 redirection data (see chapter &<<CHAPredirect>>& for more details).
6103 .cindex "Sieve filter" "enabling in default router"
6104 Traditional &_.forward_& files contain just a list of addresses, pipes, or
6105 files. Exim supports this by default. However, if &%allow_filter%& is set (it
6106 is commented out by default), the contents of the file are interpreted as a set
6107 of Exim or Sieve filtering instructions, provided the file begins with &"#Exim
6108 filter"& or &"#Sieve filter"&, respectively. User filtering is discussed in the
6109 separate document entitled &'Exim's interfaces to mail filtering'&.
6111 The &%no_verify%& and &%no_expn%& options mean that this router is skipped when
6112 verifying addresses, or when running as a consequence of an SMTP EXPN command.
6113 There are two reasons for doing this:
6116 Whether or not a local user has a &_.forward_& file is not really relevant when
6117 checking an address for validity; it makes sense not to waste resources doing
6120 More importantly, when Exim is verifying addresses or handling an EXPN
6121 command during an SMTP session, it is running as the Exim user, not as root.
6122 The group is the Exim group, and no additional groups are set up.
6123 It may therefore not be possible for Exim to read users' &_.forward_& files at
6127 The setting of &%check_ancestor%& prevents the router from generating a new
6128 address that is the same as any previous address that was redirected. (This
6129 works round a problem concerning a bad interaction between aliasing and
6130 forwarding &-- see section &<<SECTredlocmai>>&).
6132 The final three option settings specify the transports that are to be used when
6133 forwarding generates a direct delivery to a file, or to a pipe, or sets up an
6134 auto-reply, respectively. For example, if a &_.forward_& file contains
6136 a.nother@elsewhere.example, /home/spqr/archive
6138 the delivery to &_/home/spqr/archive_& is done by running the &%address_file%&
6144 # local_part_suffix = +* : -*
6145 # local_part_suffix_optional
6146 transport = local_delivery
6148 The final router sets up delivery into local mailboxes, provided that the local
6149 part is the name of a local login, by accepting the address and assigning it to
6150 the &(local_delivery)& transport. Otherwise, we have reached the end of the
6151 routers, so the address is bounced. The commented suffix settings fulfil the
6152 same purpose as they do for the &(userforward)& router.
6155 .section "Transport configuration" "SECID56"
6156 .cindex "default" "transports"
6157 .cindex "transports" "default"
6158 Transports define mechanisms for actually delivering messages. They operate
6159 only when referenced from routers, so the order in which they are defined does
6160 not matter. The transports section of the configuration starts with
6164 One remote transport and four local transports are defined.
6170 This transport is used for delivering messages over SMTP connections.
6171 The list of remote hosts comes from the router.
6172 The &%hosts_try_prdr%& option enables an efficiency SMTP option.
6173 It is negotiated between client and server
6174 and not expected to cause problems but can be disabled if needed.
6175 All other options are defaulted.
6179 file = /var/mail/$local_part
6186 This &(appendfile)& transport is used for local delivery to user mailboxes in
6187 traditional BSD mailbox format. By default it runs under the uid and gid of the
6188 local user, which requires the sticky bit to be set on the &_/var/mail_&
6189 directory. Some systems use the alternative approach of running mail deliveries
6190 under a particular group instead of using the sticky bit. The commented options
6191 show how this can be done.
6193 Exim adds three headers to the message as it delivers it: &'Delivery-date:'&,
6194 &'Envelope-to:'& and &'Return-path:'&. This action is requested by the three
6195 similarly-named options above.
6201 This transport is used for handling deliveries to pipes that are generated by
6202 redirection (aliasing or users' &_.forward_& files). The &%return_output%&
6203 option specifies that any output on stdout or stderr generated by the pipe is to
6204 be returned to the sender.
6212 This transport is used for handling deliveries to files that are generated by
6213 redirection. The name of the file is not specified in this instance of
6214 &(appendfile)&, because it comes from the &(redirect)& router.
6219 This transport is used for handling automatic replies generated by users'
6224 .section "Default retry rule" "SECID57"
6225 .cindex "retry" "default rule"
6226 .cindex "default" "retry rule"
6227 The retry section of the configuration file contains rules which affect the way
6228 Exim retries deliveries that cannot be completed at the first attempt. It is
6229 introduced by the line
6233 In the default configuration, there is just one rule, which applies to all
6236 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
6238 This causes any temporarily failing address to be retried every 15 minutes for
6239 2 hours, then at intervals starting at one hour and increasing by a factor of
6240 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address
6241 is not delivered after 4 days of temporary failure, it is bounced. The time is
6242 measured from first failure, not from the time the message was received.
6244 If the retry section is removed from the configuration, or is empty (that is,
6245 if no retry rules are defined), Exim will not retry deliveries. This turns
6246 temporary errors into permanent errors.
6249 .section "Rewriting configuration" "SECID58"
6250 The rewriting section of the configuration, introduced by
6254 contains rules for rewriting addresses in messages as they arrive. There are no
6255 rewriting rules in the default configuration file.
6259 .section "Authenticators configuration" "SECTdefconfauth"
6260 .cindex "AUTH" "configuration"
6261 The authenticators section of the configuration, introduced by
6263 begin authenticators
6265 defines mechanisms for the use of the SMTP AUTH command. The default
6266 configuration file contains two commented-out example authenticators
6267 which support plaintext username/password authentication using the
6268 standard PLAIN mechanism and the traditional but non-standard LOGIN
6269 mechanism, with Exim acting as the server. PLAIN and LOGIN are enough
6270 to support most MUA software.
6272 The example PLAIN authenticator looks like this:
6275 # driver = plaintext
6276 # server_set_id = $auth2
6277 # server_prompts = :
6278 # server_condition = Authentication is not yet configured
6279 # server_advertise_condition = ${if def:tls_in_cipher }
6281 And the example LOGIN authenticator looks like this:
6284 # driver = plaintext
6285 # server_set_id = $auth1
6286 # server_prompts = <| Username: | Password:
6287 # server_condition = Authentication is not yet configured
6288 # server_advertise_condition = ${if def:tls_in_cipher }
6291 The &%server_set_id%& option makes Exim remember the authenticated username
6292 in &$authenticated_id$&, which can be used later in ACLs or routers. The
6293 &%server_prompts%& option configures the &(plaintext)& authenticator so
6294 that it implements the details of the specific authentication mechanism,
6295 i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls
6296 when Exim offers authentication to clients; in the examples, this is only
6297 when TLS or SSL has been started, so to enable the authenticators you also
6298 need to add support for TLS as described in section &<<SECTdefconfmain>>&.
6300 The &%server_condition%& setting defines how to verify that the username and
6301 password are correct. In the examples it just produces an error message.
6302 To make the authenticators work, you can use a string expansion
6303 expression like one of the examples in chapter &<<CHAPplaintext>>&.
6305 Beware that the sequence of the parameters to PLAIN and LOGIN differ; the
6306 usercode and password are in different positions.
6307 Chapter &<<CHAPplaintext>>& covers both.
6309 .ecindex IIDconfiwal
6313 . ////////////////////////////////////////////////////////////////////////////
6314 . ////////////////////////////////////////////////////////////////////////////
6316 .chapter "Regular expressions" "CHAPregexp"
6318 .cindex "regular expressions" "library"
6320 Exim supports the use of regular expressions in many of its options. It
6321 uses the PCRE regular expression library; this provides regular expression
6322 matching that is compatible with Perl 5. The syntax and semantics of
6323 regular expressions is discussed in
6324 online Perl manpages, in
6325 many Perl reference books, and also in
6326 Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by
6327 O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)).
6329 The documentation for the syntax and semantics of the regular expressions that
6330 are supported by PCRE is included in the PCRE distribution, and no further
6331 description is included here. The PCRE functions are called from Exim using
6332 the default option settings (that is, with no PCRE options set), except that
6333 the PCRE_CASELESS option is set when the matching is required to be
6336 In most cases, when a regular expression is required in an Exim configuration,
6337 it has to start with a circumflex, in order to distinguish it from plain text
6338 or an &"ends with"& wildcard. In this example of a configuration setting, the
6339 second item in the colon-separated list is a regular expression.
6341 domains = a.b.c : ^\\d{3} : *.y.z : ...
6343 The doubling of the backslash is required because of string expansion that
6344 precedes interpretation &-- see section &<<SECTlittext>>& for more discussion
6345 of this issue, and a way of avoiding the need for doubling backslashes. The
6346 regular expression that is eventually used in this example contains just one
6347 backslash. The circumflex is included in the regular expression, and has the
6348 normal effect of &"anchoring"& it to the start of the string that is being
6351 There are, however, two cases where a circumflex is not required for the
6352 recognition of a regular expression: these are the &%match%& condition in a
6353 string expansion, and the &%matches%& condition in an Exim filter file. In
6354 these cases, the relevant string is always treated as a regular expression; if
6355 it does not start with a circumflex, the expression is not anchored, and can
6356 match anywhere in the subject string.
6358 In all cases, if you want a regular expression to match at the end of a string,
6359 you must code the $ metacharacter to indicate this. For example:
6361 domains = ^\\d{3}\\.example
6363 matches the domain &'123.example'&, but it also matches &'123.example.com'&.
6366 domains = ^\\d{3}\\.example\$
6368 if you want &'example'& to be the top-level domain. The backslash before the
6369 $ is needed because string expansion also interprets dollar characters.
6373 . ////////////////////////////////////////////////////////////////////////////
6374 . ////////////////////////////////////////////////////////////////////////////
6376 .chapter "File and database lookups" "CHAPfdlookup"
6377 .scindex IIDfidalo1 "file" "lookups"
6378 .scindex IIDfidalo2 "database" "lookups"
6379 .cindex "lookup" "description of"
6380 Exim can be configured to look up data in files or databases as it processes
6381 messages. Two different kinds of syntax are used:
6384 A string that is to be expanded may contain explicit lookup requests. These
6385 cause parts of the string to be replaced by data that is obtained from the
6386 lookup. Lookups of this type are conditional expansion items. Different results
6387 can be defined for the cases of lookup success and failure. See chapter
6388 &<<CHAPexpand>>&, where string expansions are described in detail.
6389 The key for the lookup is specified as part of the string expansion.
6391 Lists of domains, hosts, and email addresses can contain lookup requests as a
6392 way of avoiding excessively long linear lists. In this case, the data that is
6393 returned by the lookup is often (but not always) discarded; whether the lookup
6394 succeeds or fails is what really counts. These kinds of list are described in
6395 chapter &<<CHAPdomhosaddlists>>&.
6396 The key for the lookup is given by the context in which the list is expanded.
6399 String expansions, lists, and lookups interact with each other in such a way
6400 that there is no order in which to describe any one of them that does not
6401 involve references to the others. Each of these three chapters makes more sense
6402 if you have read the other two first. If you are reading this for the first
6403 time, be aware that some of it will make a lot more sense after you have read
6404 chapters &<<CHAPdomhosaddlists>>& and &<<CHAPexpand>>&.
6406 .section "Examples of different lookup syntax" "SECID60"
6407 It is easy to confuse the two different kinds of lookup, especially as the
6408 lists that may contain the second kind are always expanded before being
6409 processed as lists. Therefore, they may also contain lookups of the first kind.
6410 Be careful to distinguish between the following two examples:
6412 domains = ${lookup{$sender_host_address}lsearch{/some/file}}
6413 domains = lsearch;/some/file
6415 The first uses a string expansion, the result of which must be a domain list.
6416 No strings have been specified for a successful or a failing lookup; the
6417 defaults in this case are the looked-up data and an empty string, respectively.
6418 The expansion takes place before the string is processed as a list, and the
6419 file that is searched could contain lines like this:
6421 192.168.3.4: domain1:domain2:...
6422 192.168.1.9: domain3:domain4:...
6424 When the lookup succeeds, the result of the expansion is a list of domains (and
6425 possibly other types of item that are allowed in domain lists).
6427 In the second example, the lookup is a single item in a domain list. It causes
6428 Exim to use a lookup to see if the domain that is being processed can be found
6429 in the file. The file could contains lines like this:
6434 Any data that follows the keys is not relevant when checking that the domain
6435 matches the list item.
6437 It is possible, though no doubt confusing, to use both kinds of lookup at once.
6438 Consider a file containing lines like this:
6440 192.168.5.6: lsearch;/another/file
6442 If the value of &$sender_host_address$& is 192.168.5.6, expansion of the
6443 first &%domains%& setting above generates the second setting, which therefore
6444 causes a second lookup to occur.
6446 The rest of this chapter describes the different lookup types that are
6447 available. Any of them can be used in any part of the configuration where a
6448 lookup is permitted.
6451 .section "Lookup types" "SECID61"
6452 .cindex "lookup" "types of"
6453 .cindex "single-key lookup" "definition of"
6454 Two different types of data lookup are implemented:
6457 The &'single-key'& type requires the specification of a file in which to look,
6458 and a single key to search for. The key must be a non-empty string for the
6459 lookup to succeed. The lookup type determines how the file is searched.
6461 .cindex "query-style lookup" "definition of"
6462 The &'query-style'& type accepts a generalized database query. No particular
6463 key value is assumed by Exim for query-style lookups. You can use whichever
6464 Exim variables you need to construct the database query.
6467 The code for each lookup type is in a separate source file that is included in
6468 the binary of Exim only if the corresponding compile-time option is set. The
6469 default settings in &_src/EDITME_& are:
6474 which means that only linear searching and DBM lookups are included by default.
6475 For some types of lookup (e.g. SQL databases), you need to install appropriate
6476 libraries and header files before building Exim.
6481 .section "Single-key lookup types" "SECTsinglekeylookups"
6482 .cindex "lookup" "single-key types"
6483 .cindex "single-key lookup" "list of types"
6484 The following single-key lookup types are implemented:
6487 .cindex "cdb" "description of"
6488 .cindex "lookup" "cdb"
6489 .cindex "binary zero" "in lookup key"
6490 &(cdb)&: The given file is searched as a Constant DataBase file, using the key
6491 string without a terminating binary zero. The cdb format is designed for
6492 indexed files that are read frequently and never updated, except by total
6493 re-creation. As such, it is particularly suitable for large files containing
6494 aliases or other indexed data referenced by an MTA. Information about cdb can
6495 be found in several places:
6497 &url(http://www.pobox.com/~djb/cdb.html)
6498 &url(ftp://ftp.corpit.ru/pub/tinycdb/)
6499 &url(http://packages.debian.org/stable/utils/freecdb.html)
6501 A cdb distribution is not needed in order to build Exim with cdb support,
6502 because the code for reading cdb files is included directly in Exim itself.
6503 However, no means of building or testing cdb files is provided with Exim, so
6504 you need to obtain a cdb distribution in order to do this.
6506 .cindex "DBM" "lookup type"
6507 .cindex "lookup" "dbm"
6508 .cindex "binary zero" "in lookup key"
6509 &(dbm)&: Calls to DBM library functions are used to extract data from the given
6510 DBM file by looking up the record with the given key. A terminating binary
6511 zero is included in the key that is passed to the DBM library. See section
6512 &<<SECTdb>>& for a discussion of DBM libraries.
6514 .cindex "Berkeley DB library" "file format"
6515 For all versions of Berkeley DB, Exim uses the DB_HASH style of database
6516 when building DBM files using the &%exim_dbmbuild%& utility. However, when
6517 using Berkeley DB versions 3 or 4, it opens existing databases for reading with
6518 the DB_UNKNOWN option. This enables it to handle any of the types of database
6519 that the library supports, and can be useful for accessing DBM files created by
6520 other applications. (For earlier DB versions, DB_HASH is always used.)
6522 .cindex "lookup" "dbmjz"
6523 .cindex "lookup" "dbm &-- embedded NULs"
6525 .cindex "dbmjz lookup type"
6526 &(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is
6527 interpreted as an Exim list; the elements of the list are joined together with
6528 ASCII NUL characters to form the lookup key. An example usage would be to
6529 authenticate incoming SMTP calls using the passwords from Cyrus SASL's
6530 &_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own
6531 &(cram_md5)& authenticator.
6533 .cindex "lookup" "dbmnz"
6534 .cindex "lookup" "dbm &-- terminating zero"
6535 .cindex "binary zero" "in lookup key"
6537 .cindex "&_/etc/userdbshadow.dat_&"
6538 .cindex "dbmnz lookup type"
6539 &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero
6540 is not included in the key that is passed to the DBM library. You may need this
6541 if you want to look up data in files that are created by or shared with some
6542 other application that does not use terminating zeros. For example, you need to
6543 use &(dbmnz)& rather than &(dbm)& if you want to authenticate incoming SMTP
6544 calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's
6545 utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros
6546 by default, but has an option to omit them (see section &<<SECTdbmbuild>>&).
6548 .cindex "lookup" "dsearch"
6549 .cindex "dsearch lookup type"
6550 &(dsearch)&: The given file must be a directory; this is searched for an entry
6551 whose name is the key by calling the &[lstat()]& function. The key may not
6552 contain any forward slash characters. If &[lstat()]& succeeds, the result of
6553 the lookup is the name of the entry, which may be a file, directory,
6554 symbolic link, or any other kind of directory entry. An example of how this
6555 lookup can be used to support virtual domains is given in section
6556 &<<SECTvirtualdomains>>&.
6558 .cindex "lookup" "iplsearch"
6559 .cindex "iplsearch lookup type"
6560 &(iplsearch)&: The given file is a text file containing keys and data. A key is
6561 terminated by a colon or white space or the end of the line. The keys in the
6562 file must be IP addresses, or IP addresses with CIDR masks. Keys that involve
6563 IPv6 addresses must be enclosed in quotes to prevent the first internal colon
6564 being interpreted as a key terminator. For example:
6566 1.2.3.4: data for 1.2.3.4
6567 192.168.0.0/16: data for 192.168.0.0/16
6568 "abcd::cdab": data for abcd::cdab
6569 "abcd:abcd::/32" data for abcd:abcd::/32
6571 The key for an &(iplsearch)& lookup must be an IP address (without a mask). The
6572 file is searched linearly, using the CIDR masks where present, until a matching
6573 key is found. The first key that matches is used; there is no attempt to find a
6574 &"best"& match. Apart from the way the keys are matched, the processing for
6575 &(iplsearch)& is the same as for &(lsearch)&.
6577 &*Warning 1*&: Unlike most other single-key lookup types, a file of data for
6578 &(iplsearch)& can &'not'& be turned into a DBM or cdb file, because those
6579 lookup types support only literal keys.
6581 &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that
6582 the implicit key is the host's IP address rather than its name (see section
6583 &<<SECThoslispatsikey>>&).
6585 .cindex "linear search"
6586 .cindex "lookup" "lsearch"
6587 .cindex "lsearch lookup type"
6588 .cindex "case sensitivity" "in lsearch lookup"
6589 &(lsearch)&: The given file is a text file that is searched linearly for a
6590 line beginning with the search key, terminated by a colon or white space or the
6591 end of the line. The search is case-insensitive; that is, upper and lower case
6592 letters are treated as the same. The first occurrence of the key that is found
6593 in the file is used.
6595 White space between the key and the colon is permitted. The remainder of the
6596 line, with leading and trailing white space removed, is the data. This can be
6597 continued onto subsequent lines by starting them with any amount of white
6598 space, but only a single space character is included in the data at such a
6599 junction. If the data begins with a colon, the key must be terminated by a
6604 Empty lines and lines beginning with # are ignored, even if they occur in the
6605 middle of an item. This is the traditional textual format of alias files. Note
6606 that the keys in an &(lsearch)& file are literal strings. There is no
6607 wildcarding of any kind.
6609 .cindex "lookup" "lsearch &-- colons in keys"
6610 .cindex "white space" "in lsearch key"
6611 In most &(lsearch)& files, keys are not required to contain colons or #
6612 characters, or white space. However, if you need this feature, it is available.
6613 If a key begins with a doublequote character, it is terminated only by a
6614 matching quote (or end of line), and the normal escaping rules apply to its
6615 contents (see section &<<SECTstrings>>&). An optional colon is permitted after
6616 quoted keys (exactly as for unquoted keys). There is no special handling of
6617 quotes for the data part of an &(lsearch)& line.
6620 .cindex "NIS lookup type"
6621 .cindex "lookup" "NIS"
6622 .cindex "binary zero" "in lookup key"
6623 &(nis)&: The given file is the name of a NIS map, and a NIS lookup is done with
6624 the given key, without a terminating binary zero. There is a variant called
6625 &(nis0)& which does include the terminating binary zero in the key. This is
6626 reportedly needed for Sun-style alias files. Exim does not recognize NIS
6627 aliases; the full map names must be used.
6630 .cindex "wildlsearch lookup type"
6631 .cindex "lookup" "wildlsearch"
6632 .cindex "nwildlsearch lookup type"
6633 .cindex "lookup" "nwildlsearch"
6634 &(wildlsearch)& or &(nwildlsearch)&: These search a file linearly, like
6635 &(lsearch)&, but instead of being interpreted as a literal string, each key in
6636 the file may be wildcarded. The difference between these two lookup types is
6637 that for &(wildlsearch)&, each key in the file is string-expanded before being
6638 used, whereas for &(nwildlsearch)&, no expansion takes place.
6640 .cindex "case sensitivity" "in (n)wildlsearch lookup"
6641 Like &(lsearch)&, the testing is done case-insensitively. However, keys in the
6642 file that are regular expressions can be made case-sensitive by the use of
6643 &`(-i)`& within the pattern. The following forms of wildcard are recognized:
6645 . ==== As this is a nested list, any displays it contains must be indented
6646 . ==== as otherwise they are too far to the left.
6649 The string may begin with an asterisk to mean &"ends with"&. For example:
6651 *.a.b.c data for anything.a.b.c
6652 *fish data for anythingfish
6655 The string may begin with a circumflex to indicate a regular expression. For
6656 example, for &(wildlsearch)&:
6658 ^\N\d+\.a\.b\N data for <digits>.a.b
6660 Note the use of &`\N`& to disable expansion of the contents of the regular
6661 expression. If you are using &(nwildlsearch)&, where the keys are not
6662 string-expanded, the equivalent entry is:
6664 ^\d+\.a\.b data for <digits>.a.b
6666 The case-insensitive flag is set at the start of compiling the regular
6667 expression, but it can be turned off by using &`(-i)`& at an appropriate point.
6668 For example, to make the entire pattern case-sensitive:
6670 ^(?-i)\d+\.a\.b data for <digits>.a.b
6673 If the regular expression contains white space or colon characters, you must
6674 either quote it (see &(lsearch)& above), or represent these characters in other
6675 ways. For example, &`\s`& can be used for white space and &`\x3A`& for a
6676 colon. This may be easier than quoting, because if you quote, you have to
6677 escape all the backslashes inside the quotes.
6679 &*Note*&: It is not possible to capture substrings in a regular expression
6680 match for later use, because the results of all lookups are cached. If a lookup
6681 is repeated, the result is taken from the cache, and no actual pattern matching
6682 takes place. The values of all the numeric variables are unset after a
6683 &((n)wildlsearch)& match.
6686 Although I cannot see it being of much use, the general matching function that
6687 is used to implement &((n)wildlsearch)& means that the string may begin with a
6688 lookup name terminated by a semicolon, and followed by lookup data. For
6691 cdb;/some/file data for keys that match the file
6693 The data that is obtained from the nested lookup is discarded.
6696 Keys that do not match any of these patterns are interpreted literally. The
6697 continuation rules for the data are the same as for &(lsearch)&, and keys may
6698 be followed by optional colons.
6700 &*Warning*&: Unlike most other single-key lookup types, a file of data for
6701 &((n)wildlsearch)& can &'not'& be turned into a DBM or cdb file, because those
6702 lookup types support only literal keys.
6706 .section "Query-style lookup types" "SECTquerystylelookups"
6707 .cindex "lookup" "query-style types"
6708 .cindex "query-style lookup" "list of types"
6709 The supported query-style lookup types are listed below. Further details about
6710 many of them are given in later sections.
6713 .cindex "DNS" "as a lookup type"
6714 .cindex "lookup" "DNS"
6715 &(dnsdb)&: This does a DNS search for one or more records whose domain names
6716 are given in the supplied query. The resulting data is the contents of the
6717 records. See section &<<SECTdnsdb>>&.
6719 .cindex "InterBase lookup type"
6720 .cindex "lookup" "InterBase"
6721 &(ibase)&: This does a lookup in an InterBase database.
6723 .cindex "LDAP" "lookup type"
6724 .cindex "lookup" "LDAP"
6725 &(ldap)&: This does an LDAP lookup using a query in the form of a URL, and
6726 returns attributes from a single entry. There is a variant called &(ldapm)&
6727 that permits values from multiple entries to be returned. A third variant
6728 called &(ldapdn)& returns the Distinguished Name of a single entry instead of
6729 any attribute values. See section &<<SECTldap>>&.
6731 .cindex "MySQL" "lookup type"
6732 .cindex "lookup" "MySQL"
6733 &(mysql)&: The format of the query is an SQL statement that is passed to a
6734 MySQL database. See section &<<SECTsql>>&.
6736 .cindex "NIS+ lookup type"
6737 .cindex "lookup" "NIS+"
6738 &(nisplus)&: This does a NIS+ lookup using a query that can specify the name of
6739 the field to be returned. See section &<<SECTnisplus>>&.
6741 .cindex "Oracle" "lookup type"
6742 .cindex "lookup" "Oracle"
6743 &(oracle)&: The format of the query is an SQL statement that is passed to an
6744 Oracle database. See section &<<SECTsql>>&.
6746 .cindex "lookup" "passwd"
6747 .cindex "passwd lookup type"
6748 .cindex "&_/etc/passwd_&"
6749 &(passwd)& is a query-style lookup with queries that are just user names. The
6750 lookup calls &[getpwnam()]& to interrogate the system password data, and on
6751 success, the result string is the same as you would get from an &(lsearch)&
6752 lookup on a traditional &_/etc/passwd file_&, though with &`*`& for the
6753 password value. For example:
6755 *:42:42:King Rat:/home/kr:/bin/bash
6758 .cindex "PostgreSQL lookup type"
6759 .cindex "lookup" "PostgreSQL"
6760 &(pgsql)&: The format of the query is an SQL statement that is passed to a
6761 PostgreSQL database. See section &<<SECTsql>>&.
6764 .cindex "Redis lookup type"
6765 .cindex lookup Redis
6766 &(redis)&: The format of the query is either a simple get or simple set,
6767 passed to a Redis database. See section &<<SECTsql>>&.
6770 .cindex "sqlite lookup type"
6771 .cindex "lookup" "sqlite"
6772 &(sqlite)&: The format of the query is a file name followed by an SQL statement
6773 that is passed to an SQLite database. See section &<<SECTsqlite>>&.
6776 &(testdb)&: This is a lookup type that is used for testing Exim. It is
6777 not likely to be useful in normal operation.
6779 .cindex "whoson lookup type"
6780 .cindex "lookup" "whoson"
6781 &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that
6782 allows a server to check whether a particular (dynamically allocated) IP
6783 address is currently allocated to a known (trusted) user and, optionally, to
6784 obtain the identity of the said user. For SMTP servers, &'Whoson'& was popular
6785 at one time for &"POP before SMTP"& authentication, but that approach has been
6786 superseded by SMTP authentication. In Exim, &'Whoson'& can be used to implement
6787 &"POP before SMTP"& checking using ACL statements such as
6789 require condition = \
6790 ${lookup whoson {$sender_host_address}{yes}{no}}
6792 The query consists of a single IP address. The value returned is the name of
6793 the authenticated user, which is stored in the variable &$value$&. However, in
6794 this example, the data in &$value$& is not used; the result of the lookup is
6795 one of the fixed strings &"yes"& or &"no"&.
6800 .section "Temporary errors in lookups" "SECID63"
6801 .cindex "lookup" "temporary error in"
6802 Lookup functions can return temporary error codes if the lookup cannot be
6803 completed. For example, an SQL or LDAP database might be unavailable. For this
6804 reason, it is not advisable to use a lookup that might do this for critical
6805 options such as a list of local domains.
6807 When a lookup cannot be completed in a router or transport, delivery
6808 of the message (to the relevant address) is deferred, as for any other
6809 temporary error. In other circumstances Exim may assume the lookup has failed,
6810 or may give up altogether.
6814 .section "Default values in single-key lookups" "SECTdefaultvaluelookups"
6815 .cindex "wildcard lookups"
6816 .cindex "lookup" "default values"
6817 .cindex "lookup" "wildcard"
6818 .cindex "lookup" "* added to type"
6819 .cindex "default" "in single-key lookups"
6820 In this context, a &"default value"& is a value specified by the administrator
6821 that is to be used if a lookup fails.
6823 &*Note:*& This section applies only to single-key lookups. For query-style
6824 lookups, the facilities of the query language must be used. An attempt to
6825 specify a default for a query-style lookup provokes an error.
6827 If &"*"& is added to a single-key lookup type (for example, &%lsearch*%&)
6828 and the initial lookup fails, the key &"*"& is looked up in the file to
6829 provide a default value. See also the section on partial matching below.
6831 .cindex "*@ with single-key lookup"
6832 .cindex "lookup" "*@ added to type"
6833 .cindex "alias file" "per-domain default"
6834 Alternatively, if &"*@"& is added to a single-key lookup type (for example
6835 &%dbm*@%&) then, if the initial lookup fails and the key contains an @
6836 character, a second lookup is done with everything before the last @ replaced
6837 by *. This makes it possible to provide per-domain defaults in alias files
6838 that include the domains in the keys. If the second lookup fails (or doesn't
6839 take place because there is no @ in the key), &"*"& is looked up.
6840 For example, a &(redirect)& router might contain:
6842 data = ${lookup{$local_part@$domain}lsearch*@{/etc/mix-aliases}}
6844 Suppose the address that is being processed is &'jane@eyre.example'&. Exim
6845 looks up these keys, in this order:
6851 The data is taken from whichever key it finds first. &*Note*&: In an
6852 &(lsearch)& file, this does not mean the first of these keys in the file. A
6853 complete scan is done for each key, and only if it is not found at all does
6854 Exim move on to try the next key.
6858 .section "Partial matching in single-key lookups" "SECTpartiallookup"
6859 .cindex "partial matching"
6860 .cindex "wildcard lookups"
6861 .cindex "lookup" "partial matching"
6862 .cindex "lookup" "wildcard"
6863 .cindex "asterisk" "in search type"
6864 The normal operation of a single-key lookup is to search the file for an exact
6865 match with the given key. However, in a number of situations where domains are
6866 being looked up, it is useful to be able to do partial matching. In this case,
6867 information in the file that has a key starting with &"*."& is matched by any
6868 domain that ends with the components that follow the full stop. For example, if
6869 a key in a DBM file is
6871 *.dates.fict.example
6873 then when partial matching is enabled this is matched by (amongst others)
6874 &'2001.dates.fict.example'& and &'1984.dates.fict.example'&. It is also matched
6875 by &'dates.fict.example'&, if that does not appear as a separate key in the
6878 &*Note*&: Partial matching is not available for query-style lookups. It is
6879 also not available for any lookup items in address lists (see section
6880 &<<SECTaddresslist>>&).
6882 Partial matching is implemented by doing a series of separate lookups using
6883 keys constructed by modifying the original subject key. This means that it can
6884 be used with any of the single-key lookup types, provided that
6885 partial matching keys
6886 beginning with a special prefix (default &"*."&) are included in the data file.
6887 Keys in the file that do not begin with the prefix are matched only by
6888 unmodified subject keys when partial matching is in use.
6890 Partial matching is requested by adding the string &"partial-"& to the front of
6891 the name of a single-key lookup type, for example, &%partial-dbm%&. When this
6892 is done, the subject key is first looked up unmodified; if that fails, &"*."&
6893 is added at the start of the subject key, and it is looked up again. If that
6894 fails, further lookups are tried with dot-separated components removed from the
6895 start of the subject key, one-by-one, and &"*."& added on the front of what
6898 A minimum number of two non-* components are required. This can be adjusted
6899 by including a number before the hyphen in the search type. For example,
6900 &%partial3-lsearch%& specifies a minimum of three non-* components in the
6901 modified keys. Omitting the number is equivalent to &"partial2-"&. If the
6902 subject key is &'2250.dates.fict.example'& then the following keys are looked
6903 up when the minimum number of non-* components is two:
6905 2250.dates.fict.example
6906 *.2250.dates.fict.example
6907 *.dates.fict.example
6910 As soon as one key in the sequence is successfully looked up, the lookup
6913 .cindex "lookup" "partial matching &-- changing prefix"
6914 .cindex "prefix" "for partial matching"
6915 The use of &"*."& as the partial matching prefix is a default that can be
6916 changed. The motivation for this feature is to allow Exim to operate with file
6917 formats that are used by other MTAs. A different prefix can be supplied in
6918 parentheses instead of the hyphen after &"partial"&. For example:
6920 domains = partial(.)lsearch;/some/file
6922 In this example, if the domain is &'a.b.c'&, the sequence of lookups is
6923 &`a.b.c`&, &`.a.b.c`&, and &`.b.c`& (the default minimum of 2 non-wild
6924 components is unchanged). The prefix may consist of any punctuation characters
6925 other than a closing parenthesis. It may be empty, for example:
6927 domains = partial1()cdb;/some/file
6929 For this example, if the domain is &'a.b.c'&, the sequence of lookups is
6930 &`a.b.c`&, &`b.c`&, and &`c`&.
6932 If &"partial0"& is specified, what happens at the end (when the lookup with
6933 just one non-wild component has failed, and the original key is shortened right
6934 down to the null string) depends on the prefix:
6937 If the prefix has zero length, the whole lookup fails.
6939 If the prefix has length 1, a lookup for just the prefix is done. For
6940 example, the final lookup for &"partial0(.)"& is for &`.`& alone.
6942 Otherwise, if the prefix ends in a dot, the dot is removed, and the
6943 remainder is looked up. With the default prefix, therefore, the final lookup is
6944 for &"*"& on its own.
6946 Otherwise, the whole prefix is looked up.
6950 If the search type ends in &"*"& or &"*@"& (see section
6951 &<<SECTdefaultvaluelookups>>& above), the search for an ultimate default that
6952 this implies happens after all partial lookups have failed. If &"partial0"& is
6953 specified, adding &"*"& to the search type has no effect with the default
6954 prefix, because the &"*"& key is already included in the sequence of partial
6955 lookups. However, there might be a use for lookup types such as
6956 &"partial0(.)lsearch*"&.
6958 The use of &"*"& in lookup partial matching differs from its use as a wildcard
6959 in domain lists and the like. Partial matching works only in terms of
6960 dot-separated components; a key such as &`*fict.example`&
6961 in a database file is useless, because the asterisk in a partial matching
6962 subject key is always followed by a dot.
6967 .section "Lookup caching" "SECID64"
6968 .cindex "lookup" "caching"
6969 .cindex "caching" "lookup data"
6970 Exim caches all lookup results in order to avoid needless repetition of
6971 lookups. However, because (apart from the daemon) Exim operates as a collection
6972 of independent, short-lived processes, this caching applies only within a
6973 single Exim process. There is no inter-process lookup caching facility.
6975 For single-key lookups, Exim keeps the relevant files open in case there is
6976 another lookup that needs them. In some types of configuration this can lead to
6977 many files being kept open for messages with many recipients. To avoid hitting
6978 the operating system limit on the number of simultaneously open files, Exim
6979 closes the least recently used file when it needs to open more files than its
6980 own internal limit, which can be changed via the &%lookup_open_max%& option.
6982 The single-key lookup files are closed and the lookup caches are flushed at
6983 strategic points during delivery &-- for example, after all routing is
6989 .section "Quoting lookup data" "SECID65"
6990 .cindex "lookup" "quoting"
6991 .cindex "quoting" "in lookups"
6992 When data from an incoming message is included in a query-style lookup, there
6993 is the possibility of special characters in the data messing up the syntax of
6994 the query. For example, a NIS+ query that contains
6998 will be broken if the local part happens to contain a closing square bracket.
6999 For NIS+, data can be enclosed in double quotes like this:
7001 [name="$local_part"]
7003 but this still leaves the problem of a double quote in the data. The rule for
7004 NIS+ is that double quotes must be doubled. Other lookup types have different
7005 rules, and to cope with the differing requirements, an expansion operator
7006 of the following form is provided:
7008 ${quote_<lookup-type>:<string>}
7010 For example, the safest way to write the NIS+ query is
7012 [name="${quote_nisplus:$local_part}"]
7014 See chapter &<<CHAPexpand>>& for full coverage of string expansions. The quote
7015 operator can be used for all lookup types, but has no effect for single-key
7016 lookups, since no quoting is ever needed in their key strings.
7021 .section "More about dnsdb" "SECTdnsdb"
7022 .cindex "dnsdb lookup"
7023 .cindex "lookup" "dnsdb"
7024 .cindex "DNS" "as a lookup type"
7025 The &(dnsdb)& lookup type uses the DNS as its database. A simple query consists
7026 of a record type and a domain name, separated by an equals sign. For example,
7027 an expansion string could contain:
7029 ${lookup dnsdb{mx=a.b.example}{$value}fail}
7031 If the lookup succeeds, the result is placed in &$value$&, which in this case
7032 is used on its own as the result. If the lookup does not succeed, the
7033 &`fail`& keyword causes a &'forced expansion failure'& &-- see section
7034 &<<SECTforexpfai>>& for an explanation of what this means.
7036 The supported DNS record types are A, CNAME, MX, NS, PTR, SOA, SPF, SRV, TLSA
7037 and TXT, and, when Exim is compiled with IPv6 support, AAAA.
7038 If no type is given, TXT is assumed.
7040 For any record type, if multiple records are found, the data is returned as a
7041 concatenation, with newline as the default separator. The order, of course,
7042 depends on the DNS resolver. You can specify a different separator character
7043 between multiple records by putting a right angle-bracket followed immediately
7044 by the new separator at the start of the query. For example:
7046 ${lookup dnsdb{>: a=host1.example}}
7048 It is permitted to specify a space as the separator character. Further
7049 white space is ignored.
7050 For lookup types that return multiple fields per record,
7051 an alternate field separator can be specified using a comma after the main
7052 separator character, followed immediately by the field separator.
7054 .cindex "PTR record" "in &(dnsdb)& lookup"
7055 When the type is PTR,
7056 the data can be an IP address, written as normal; inversion and the addition of
7057 &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example:
7059 ${lookup dnsdb{ptr=192.168.4.5}{$value}fail}
7061 If the data for a PTR record is not a syntactically valid IP address, it is not
7062 altered and nothing is added.
7064 .cindex "MX record" "in &(dnsdb)& lookup"
7065 .cindex "SRV record" "in &(dnsdb)& lookup"
7066 For an MX lookup, both the preference value and the host name are returned for
7067 each record, separated by a space. For an SRV lookup, the priority, weight,
7068 port, and host name are returned for each record, separated by spaces.
7069 The field separator can be modified as above.
7071 .cindex "TXT record" "in &(dnsdb)& lookup"
7072 .cindex "SPF record" "in &(dnsdb)& lookup"
7073 For TXT records with multiple items of data, only the first item is returned,
7074 unless a field separator is specified.
7075 To concatenate items without a separator, use a semicolon instead.
7077 default behaviour is to concatenate multiple items without using a separator.
7079 ${lookup dnsdb{>\n,: txt=a.b.example}}
7080 ${lookup dnsdb{>\n; txt=a.b.example}}
7081 ${lookup dnsdb{spf=example.org}}
7083 It is permitted to specify a space as the separator character. Further
7084 white space is ignored.
7086 .cindex "SOA record" "in &(dnsdb)& lookup"
7087 For an SOA lookup, while no result is obtained the lookup is redone with
7088 successively more leading components dropped from the given domain.
7089 Only the primary-nameserver field is returned unless a field separator is
7092 ${lookup dnsdb{>:,; soa=a.b.example.com}}
7095 .section "Dnsdb lookup modifiers" "SECTdnsdb_mod"
7096 .cindex "dnsdb modifiers"
7097 .cindex "modifiers" "dnsdb"
7098 .cindex "options" "dnsdb"
7099 Modifiers for &(dnsdb)& lookups are given by optional keywords,
7100 each followed by a comma,
7101 that may appear before the record type.
7103 The &(dnsdb)& lookup fails only if all the DNS lookups fail. If there is a
7104 temporary DNS error for any of them, the behaviour is controlled by
7105 a defer-option modifier.
7106 The possible keywords are
7107 &"defer_strict"&, &"defer_never"&, and &"defer_lax"&.
7108 With &"strict"& behaviour, any temporary DNS error causes the
7109 whole lookup to defer. With &"never"& behaviour, a temporary DNS error is
7110 ignored, and the behaviour is as if the DNS lookup failed to find anything.
7111 With &"lax"& behaviour, all the queries are attempted, but a temporary DNS
7112 error causes the whole lookup to defer only if none of the other lookups
7113 succeed. The default is &"lax"&, so the following lookups are equivalent:
7115 ${lookup dnsdb{defer_lax,a=one.host.com:two.host.com}}
7116 ${lookup dnsdb{a=one.host.com:two.host.com}}
7118 Thus, in the default case, as long as at least one of the DNS lookups
7119 yields some data, the lookup succeeds.
7121 .cindex "DNSSEC" "dns lookup"
7122 Use of &(DNSSEC)& is controlled by a dnssec modifier.
7123 The possible keywords are
7124 &"dnssec_strict"&, &"dnssec_lax"&, and &"dnssec_never"&.
7125 With &"strict"& or &"lax"& DNSSEC information is requested
7127 With &"strict"& a response from the DNS resolver that
7128 is not labelled as authenticated data
7129 is treated as equivalent to a temporary DNS error.
7130 The default is &"never"&.
7132 See also the &$lookup_dnssec_authenticated$& variable.
7134 .cindex timeout "dns lookup"
7135 .cindex "DNS" timeout
7136 Timeout for the dnsdb lookup can be controlled by a retrans modifier.
7137 The form is &"retrans_VAL"& where VAL is an Exim time specification
7139 The default value is set by the main configuration option &%dns_retrans%&.
7141 Retries for the dnsdb lookup can be controlled by a retry modifier.
7142 The form if &"retry_VAL"& where VAL is an integer.
7143 The default count is set by the main configuration option &%dns_retry%&.
7145 .cindex caching "of dns lookup"
7146 .cindex TTL "of dns lookup"
7148 Dnsdb lookup results are cached within a single process (and its children).
7149 The cache entry lifetime is limited to the smallest time-to-live (TTL)
7150 value of the set of returned DNS records.
7153 .section "Pseudo dnsdb record types" "SECID66"
7154 .cindex "MX record" "in &(dnsdb)& lookup"
7155 By default, both the preference value and the host name are returned for
7156 each MX record, separated by a space. If you want only host names, you can use
7157 the pseudo-type MXH:
7159 ${lookup dnsdb{mxh=a.b.example}}
7161 In this case, the preference values are omitted, and just the host names are
7164 .cindex "name server for enclosing domain"
7165 Another pseudo-type is ZNS (for &"zone NS"&). It performs a lookup for NS
7166 records on the given domain, but if none are found, it removes the first
7167 component of the domain name, and tries again. This process continues until NS
7168 records are found or there are no more components left (or there is a DNS
7169 error). In other words, it may return the name servers for a top-level domain,
7170 but it never returns the root name servers. If there are no NS records for the
7171 top-level domain, the lookup fails. Consider these examples:
7173 ${lookup dnsdb{zns=xxx.quercite.com}}
7174 ${lookup dnsdb{zns=xxx.edu}}
7176 Assuming that in each case there are no NS records for the full domain name,
7177 the first returns the name servers for &%quercite.com%&, and the second returns
7178 the name servers for &%edu%&.
7180 You should be careful about how you use this lookup because, unless the
7181 top-level domain does not exist, the lookup always returns some host names. The
7182 sort of use to which this might be put is for seeing if the name servers for a
7183 given domain are on a blacklist. You can probably assume that the name servers
7184 for the high-level domains such as &%com%& or &%co.uk%& are not going to be on
7187 .cindex "CSA" "in &(dnsdb)& lookup"
7188 A third pseudo-type is CSA (Client SMTP Authorization). This looks up SRV
7189 records according to the CSA rules, which are described in section
7190 &<<SECTverifyCSA>>&. Although &(dnsdb)& supports SRV lookups directly, this is
7191 not sufficient because of the extra parent domain search behaviour of CSA. The
7192 result of a successful lookup such as:
7194 ${lookup dnsdb {csa=$sender_helo_name}}
7196 has two space-separated fields: an authorization code and a target host name.
7197 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
7198 authorization required but absent, or &"?"& for unknown.
7200 .cindex "A+" "in &(dnsdb)& lookup"
7201 The pseudo-type A+ performs an AAAA
7202 and then an A lookup. All results are returned; defer processing
7203 (see below) is handled separately for each lookup. Example:
7205 ${lookup dnsdb {>; a+=$sender_helo_name}}
7209 .section "Multiple dnsdb lookups" "SECID67"
7210 In the previous sections, &(dnsdb)& lookups for a single domain are described.
7211 However, you can specify a list of domains or IP addresses in a single
7212 &(dnsdb)& lookup. The list is specified in the normal Exim way, with colon as
7213 the default separator, but with the ability to change this. For example:
7215 ${lookup dnsdb{one.domain.com:two.domain.com}}
7216 ${lookup dnsdb{a=one.host.com:two.host.com}}
7217 ${lookup dnsdb{ptr = <; 1.2.3.4 ; 4.5.6.8}}
7219 In order to retain backwards compatibility, there is one special case: if
7220 the lookup type is PTR and no change of separator is specified, Exim looks
7221 to see if the rest of the string is precisely one IPv6 address. In this
7222 case, it does not treat it as a list.
7224 The data from each lookup is concatenated, with newline separators by default,
7225 in the same way that multiple DNS records for a single item are handled. A
7226 different separator can be specified, as described above.
7231 .section "More about LDAP" "SECTldap"
7232 .cindex "LDAP" "lookup, more about"
7233 .cindex "lookup" "LDAP"
7234 .cindex "Solaris" "LDAP"
7235 The original LDAP implementation came from the University of Michigan; this has
7236 become &"Open LDAP"&, and there are now two different releases. Another
7237 implementation comes from Netscape, and Solaris 7 and subsequent releases
7238 contain inbuilt LDAP support. Unfortunately, though these are all compatible at
7239 the lookup function level, their error handling is different. For this reason
7240 it is necessary to set a compile-time variable when building Exim with LDAP, to
7241 indicate which LDAP library is in use. One of the following should appear in
7242 your &_Local/Makefile_&:
7244 LDAP_LIB_TYPE=UMICHIGAN
7245 LDAP_LIB_TYPE=OPENLDAP1
7246 LDAP_LIB_TYPE=OPENLDAP2
7247 LDAP_LIB_TYPE=NETSCAPE
7248 LDAP_LIB_TYPE=SOLARIS
7250 If LDAP_LIB_TYPE is not set, Exim assumes &`OPENLDAP1`&, which has the
7251 same interface as the University of Michigan version.
7253 There are three LDAP lookup types in Exim. These behave slightly differently in
7254 the way they handle the results of a query:
7257 &(ldap)& requires the result to contain just one entry; if there are more, it
7260 &(ldapdn)& also requires the result to contain just one entry, but it is the
7261 Distinguished Name that is returned rather than any attribute values.
7263 &(ldapm)& permits the result to contain more than one entry; the attributes
7264 from all of them are returned.
7268 For &(ldap)& and &(ldapm)&, if a query finds only entries with no attributes,
7269 Exim behaves as if the entry did not exist, and the lookup fails. The format of
7270 the data returned by a successful lookup is described in the next section.
7271 First we explain how LDAP queries are coded.
7274 .section "Format of LDAP queries" "SECTforldaque"
7275 .cindex "LDAP" "query format"
7276 An LDAP query takes the form of a URL as defined in RFC 2255. For example, in
7277 the configuration of a &(redirect)& router one might have this setting:
7279 data = ${lookup ldap \
7280 {ldap:///cn=$local_part,o=University%20of%20Cambridge,\
7281 c=UK?mailbox?base?}}
7283 .cindex "LDAP" "with TLS"
7284 The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports
7285 secure (encrypted) LDAP connections. The second of these ensures that an
7286 encrypted TLS connection is used.
7288 With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular
7289 LDAP connections, rather than the SSL-on-connect &`ldaps`&.
7290 See the &%ldap_start_tls%& option.
7292 Starting with Exim 4.83, the initialization of LDAP with TLS is more tightly
7293 controlled. Every part of the TLS configuration can be configured by settings in
7294 &_exim.conf_&. Depending on the version of the client libraries installed on
7295 your system, some of the initialization may have required setting options in
7296 &_/etc/ldap.conf_& or &_~/.ldaprc_& to get TLS working with self-signed
7297 certificates. This revealed a nuance where the current UID that exim was
7298 running as could affect which config files it read. With Exim 4.83, these
7299 methods become optional, only taking effect if not specifically set in
7303 .section "LDAP quoting" "SECID68"
7304 .cindex "LDAP" "quoting"
7305 Two levels of quoting are required in LDAP queries, the first for LDAP itself
7306 and the second because the LDAP query is represented as a URL. Furthermore,
7307 within an LDAP query, two different kinds of quoting are required. For this
7308 reason, there are two different LDAP-specific quoting operators.
7310 The &%quote_ldap%& operator is designed for use on strings that are part of
7311 filter specifications. Conceptually, it first does the following conversions on
7319 in accordance with RFC 2254. The resulting string is then quoted according
7320 to the rules for URLs, that is, all non-alphanumeric characters except
7324 are converted to their hex values, preceded by a percent sign. For example:
7326 ${quote_ldap: a(bc)*, a<yz>; }
7330 %20a%5C28bc%5C29%5C2A%2C%20a%3Cyz%3E%3B%20
7332 Removing the URL quoting, this is (with a leading and a trailing space):
7334 a\28bc\29\2A, a<yz>;
7336 The &%quote_ldap_dn%& operator is designed for use on strings that are part of
7337 base DN specifications in queries. Conceptually, it first converts the string
7338 by inserting a backslash in front of any of the following characters:
7342 It also inserts a backslash before any leading spaces or # characters, and
7343 before any trailing spaces. (These rules are in RFC 2253.) The resulting string
7344 is then quoted according to the rules for URLs. For example:
7346 ${quote_ldap_dn: a(bc)*, a<yz>; }
7350 %5C%20a(bc)*%5C%2C%20a%5C%3Cyz%5C%3E%5C%3B%5C%20
7352 Removing the URL quoting, this is (with a trailing space):
7354 \ a(bc)*\, a\<yz\>\;\
7356 There are some further comments about quoting in the section on LDAP
7357 authentication below.
7360 .section "LDAP connections" "SECID69"
7361 .cindex "LDAP" "connections"
7362 The connection to an LDAP server may either be over TCP/IP, or, when OpenLDAP
7363 is in use, via a Unix domain socket. The example given above does not specify
7364 an LDAP server. A server that is reached by TCP/IP can be specified in a query
7367 ldap://<hostname>:<port>/...
7369 If the port (and preceding colon) are omitted, the standard LDAP port (389) is
7370 used. When no server is specified in a query, a list of default servers is
7371 taken from the &%ldap_default_servers%& configuration option. This supplies a
7372 colon-separated list of servers which are tried in turn until one successfully
7373 handles a query, or there is a serious error. Successful handling either
7374 returns the requested data, or indicates that it does not exist. Serious errors
7375 are syntactical, or multiple values when only a single value is expected.
7376 Errors which cause the next server to be tried are connection failures, bind
7377 failures, and timeouts.
7379 For each server name in the list, a port number can be given. The standard way
7380 of specifying a host and port is to use a colon separator (RFC 1738). Because
7381 &%ldap_default_servers%& is a colon-separated list, such colons have to be
7382 doubled. For example
7384 ldap_default_servers = ldap1.example.com::145:ldap2.example.com
7386 If &%ldap_default_servers%& is unset, a URL with no server name is passed
7387 to the LDAP library with no server name, and the library's default (normally
7388 the local host) is used.
7390 If you are using the OpenLDAP library, you can connect to an LDAP server using
7391 a Unix domain socket instead of a TCP/IP connection. This is specified by using
7392 &`ldapi`& instead of &`ldap`& in LDAP queries. What follows here applies only
7393 to OpenLDAP. If Exim is compiled with a different LDAP library, this feature is
7396 For this type of connection, instead of a host name for the server, a pathname
7397 for the socket is required, and the port number is not relevant. The pathname
7398 can be specified either as an item in &%ldap_default_servers%&, or inline in
7399 the query. In the former case, you can have settings such as
7401 ldap_default_servers = /tmp/ldap.sock : backup.ldap.your.domain
7403 When the pathname is given in the query, you have to escape the slashes as
7404 &`%2F`& to fit in with the LDAP URL syntax. For example:
7406 ${lookup ldap {ldapi://%2Ftmp%2Fldap.sock/o=...
7408 When Exim processes an LDAP lookup and finds that the &"hostname"& is really
7409 a pathname, it uses the Unix domain socket code, even if the query actually
7410 specifies &`ldap`& or &`ldaps`&. In particular, no encryption is used for a
7411 socket connection. This behaviour means that you can use a setting of
7412 &%ldap_default_servers%& such as in the example above with traditional &`ldap`&
7413 or &`ldaps`& queries, and it will work. First, Exim tries a connection via
7414 the Unix domain socket; if that fails, it tries a TCP/IP connection to the
7417 If an explicit &`ldapi`& type is given in a query when a host name is
7418 specified, an error is diagnosed. However, if there are more items in
7419 &%ldap_default_servers%&, they are tried. In other words:
7422 Using a pathname with &`ldap`& or &`ldaps`& forces the use of the Unix domain
7425 Using &`ldapi`& with a host name causes an error.
7429 Using &`ldapi`& with no host or path in the query, and no setting of
7430 &%ldap_default_servers%&, does whatever the library does by default.
7434 .section "LDAP authentication and control information" "SECID70"
7435 .cindex "LDAP" "authentication"
7436 The LDAP URL syntax provides no way of passing authentication and other control
7437 information to the server. To make this possible, the URL in an LDAP query may
7438 be preceded by any number of <&'name'&>=<&'value'&> settings, separated by
7439 spaces. If a value contains spaces it must be enclosed in double quotes, and
7440 when double quotes are used, backslash is interpreted in the usual way inside
7441 them. The following names are recognized:
7443 &`DEREFERENCE`& set the dereferencing parameter
7444 &`NETTIME `& set a timeout for a network operation
7445 &`USER `& set the DN, for authenticating the LDAP bind
7446 &`PASS `& set the password, likewise
7447 &`REFERRALS `& set the referrals parameter
7448 &`SERVERS `& set alternate server list for this query only
7449 &`SIZE `& set the limit for the number of entries returned
7450 &`TIME `& set the maximum waiting time for a query
7452 The value of the DEREFERENCE parameter must be one of the words &"never"&,
7453 &"searching"&, &"finding"&, or &"always"&. The value of the REFERRALS parameter
7454 must be &"follow"& (the default) or &"nofollow"&. The latter stops the LDAP
7455 library from trying to follow referrals issued by the LDAP server.
7457 .cindex LDAP timeout
7458 .cindex timeout "LDAP lookup"
7459 The name CONNECT is an obsolete name for NETTIME, retained for
7460 backwards compatibility. This timeout (specified as a number of seconds) is
7461 enforced from the client end for operations that can be carried out over a
7462 network. Specifically, it applies to network connections and calls to the
7463 &'ldap_result()'& function. If the value is greater than zero, it is used if
7464 LDAP_OPT_NETWORK_TIMEOUT is defined in the LDAP headers (OpenLDAP), or
7465 if LDAP_X_OPT_CONNECT_TIMEOUT is defined in the LDAP headers (Netscape
7466 SDK 4.1). A value of zero forces an explicit setting of &"no timeout"& for
7467 Netscape SDK; for OpenLDAP no action is taken.
7469 The TIME parameter (also a number of seconds) is passed to the server to
7470 set a server-side limit on the time taken to complete a search.
7472 The SERVERS parameter allows you to specify an alternate list of ldap servers
7473 to use for an individual lookup. The global &%ldap_default_servers%& option provides a
7474 default list of ldap servers, and a single lookup can specify a single ldap
7475 server to use. But when you need to do a lookup with a list of servers that is
7476 different than the default list (maybe different order, maybe a completely
7477 different set of servers), the SERVERS parameter allows you to specify this
7478 alternate list (colon-separated).
7480 Here is an example of an LDAP query in an Exim lookup that uses some of these
7481 values. This is a single line, folded to fit on the page:
7484 {user="cn=manager,o=University of Cambridge,c=UK" pass=secret
7485 ldap:///o=University%20of%20Cambridge,c=UK?sn?sub?(cn=foo)}
7488 The encoding of spaces as &`%20`& is a URL thing which should not be done for
7489 any of the auxiliary data. Exim configuration settings that include lookups
7490 which contain password information should be preceded by &"hide"& to prevent
7491 non-admin users from using the &%-bP%& option to see their values.
7493 The auxiliary data items may be given in any order. The default is no
7494 connection timeout (the system timeout is used), no user or password, no limit
7495 on the number of entries returned, and no time limit on queries.
7497 When a DN is quoted in the USER= setting for LDAP authentication, Exim
7498 removes any URL quoting that it may contain before passing it LDAP. Apparently
7499 some libraries do this for themselves, but some do not. Removing the URL
7500 quoting has two advantages:
7503 It makes it possible to use the same &%quote_ldap_dn%& expansion for USER=
7504 DNs as with DNs inside actual queries.
7506 It permits spaces inside USER= DNs.
7509 For example, a setting such as
7511 USER=cn=${quote_ldap_dn:$1}
7513 should work even if &$1$& contains spaces.
7515 Expanded data for the PASS= value should be quoted using the &%quote%&
7516 expansion operator, rather than the LDAP quote operators. The only reason this
7517 field needs quoting is to ensure that it conforms to the Exim syntax, which
7518 does not allow unquoted spaces. For example:
7522 The LDAP authentication mechanism can be used to check passwords as part of
7523 SMTP authentication. See the &%ldapauth%& expansion string condition in chapter
7528 .section "Format of data returned by LDAP" "SECID71"
7529 .cindex "LDAP" "returned data formats"
7530 The &(ldapdn)& lookup type returns the Distinguished Name from a single entry
7531 as a sequence of values, for example
7533 cn=manager,o=University of Cambridge,c=UK
7535 The &(ldap)& lookup type generates an error if more than one entry matches the
7536 search filter, whereas &(ldapm)& permits this case, and inserts a newline in
7537 the result between the data from different entries. It is possible for multiple
7538 values to be returned for both &(ldap)& and &(ldapm)&, but in the former case
7539 you know that whatever values are returned all came from a single entry in the
7542 In the common case where you specify a single attribute in your LDAP query, the
7543 result is not quoted, and does not contain the attribute name. If the attribute
7544 has multiple values, they are separated by commas. Any comma that is
7545 part of an attribute's value is doubled.
7547 If you specify multiple attributes, the result contains space-separated, quoted
7548 strings, each preceded by the attribute name and an equals sign. Within the
7549 quotes, the quote character, backslash, and newline are escaped with
7550 backslashes, and commas are used to separate multiple values for the attribute.
7551 Any commas in attribute values are doubled
7552 (permitting treatment of the values as a comma-separated list).
7553 Apart from the escaping, the string within quotes takes the same form as the
7554 output when a single attribute is requested. Specifying no attributes is the
7555 same as specifying all of an entry's attributes.
7557 Here are some examples of the output format. The first line of each pair is an
7558 LDAP query, and the second is the data that is returned. The attribute called
7559 &%attr1%& has two values, one of them with an embedded comma, whereas
7560 &%attr2%& has only one value. Both attributes are derived from &%attr%&
7561 (they have SUP &%attr%& in their schema definitions).
7564 ldap:///o=base?attr1?sub?(uid=fred)
7567 ldap:///o=base?attr2?sub?(uid=fred)
7570 ldap:///o=base?attr?sub?(uid=fred)
7571 value1.1,value1,,2,value two
7573 ldap:///o=base?attr1,attr2?sub?(uid=fred)
7574 attr1="value1.1,value1,,2" attr2="value two"
7576 ldap:///o=base??sub?(uid=fred)
7577 objectClass="top" attr1="value1.1,value1,,2" attr2="value two"
7580 make use of Exim's &%-be%& option to run expansion tests and thereby check the
7581 results of LDAP lookups.
7582 The &%extract%& operator in string expansions can be used to pick out
7583 individual fields from data that consists of &'key'&=&'value'& pairs.
7584 The &%listextract%& operator should be used to pick out individual values
7585 of attributes, even when only a single value is expected.
7586 The doubling of embedded commas allows you to use the returned data as a
7587 comma separated list (using the "<," syntax for changing the input list separator).
7592 .section "More about NIS+" "SECTnisplus"
7593 .cindex "NIS+ lookup type"
7594 .cindex "lookup" "NIS+"
7595 NIS+ queries consist of a NIS+ &'indexed name'& followed by an optional colon
7596 and field name. If this is given, the result of a successful query is the
7597 contents of the named field; otherwise the result consists of a concatenation
7598 of &'field-name=field-value'& pairs, separated by spaces. Empty values and
7599 values containing spaces are quoted. For example, the query
7601 [name=mg1456],passwd.org_dir
7603 might return the string
7605 name=mg1456 passwd="" uid=999 gid=999 gcos="Martin Guerre"
7606 home=/home/mg1456 shell=/bin/bash shadow=""
7608 (split over two lines here to fit on the page), whereas
7610 [name=mg1456],passwd.org_dir:gcos
7616 with no quotes. A NIS+ lookup fails if NIS+ returns more than one table entry
7617 for the given indexed key. The effect of the &%quote_nisplus%& expansion
7618 operator is to double any quote characters within the text.
7622 .section "SQL lookups" "SECTsql"
7623 .cindex "SQL lookup types"
7624 .cindex "MySQL" "lookup type"
7625 .cindex "PostgreSQL lookup type"
7626 .cindex "lookup" "MySQL"
7627 .cindex "lookup" "PostgreSQL"
7628 .cindex "Oracle" "lookup type"
7629 .cindex "lookup" "Oracle"
7630 .cindex "InterBase lookup type"
7631 .cindex "lookup" "InterBase"
7632 .cindex "Redis lookup type"
7633 .cindex lookup Redis
7634 Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, Redis,
7636 databases. Queries for these databases contain SQL statements, so an example
7639 ${lookup mysql{select mailbox from users where id='userx'}\
7642 If the result of the query contains more than one field, the data for each
7643 field in the row is returned, preceded by its name, so the result of
7645 ${lookup pgsql{select home,name from users where id='userx'}\
7650 home=/home/userx name="Mister X"
7652 Empty values and values containing spaces are double quoted, with embedded
7653 quotes escaped by a backslash. If the result of the query contains just one
7654 field, the value is passed back verbatim, without a field name, for example:
7658 If the result of the query yields more than one row, it is all concatenated,
7659 with a newline between the data for each row.
7662 .section "More about MySQL, PostgreSQL, Oracle, InterBase, and Redis" "SECID72"
7663 .cindex "MySQL" "lookup type"
7664 .cindex "PostgreSQL lookup type"
7665 .cindex "lookup" "MySQL"
7666 .cindex "lookup" "PostgreSQL"
7667 .cindex "Oracle" "lookup type"
7668 .cindex "lookup" "Oracle"
7669 .cindex "InterBase lookup type"
7670 .cindex "lookup" "InterBase"
7671 .cindex "Redis lookup type"
7672 .cindex lookup Redis
7673 If any MySQL, PostgreSQL, Oracle, InterBase or Redis lookups are used, the
7674 &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, &%ibase_servers%&,
7675 or &%redis_servers%&
7676 option (as appropriate) must be set to a colon-separated list of server
7678 (For MySQL and PostgreSQL, the global option need not be set if all
7679 queries contain their own server information &-- see section
7680 &<<SECTspeserque>>&.)
7682 each item in the list is a slash-separated list of four
7683 items: host name, database name, user name, and password. In the case of
7684 Oracle, the host name field is used for the &"service name"&, and the database
7685 name field is not used and should be empty. For example:
7687 hide oracle_servers = oracle.plc.example//userx/abcdwxyz
7689 Because password data is sensitive, you should always precede the setting with
7690 &"hide"&, to prevent non-admin users from obtaining the setting via the &%-bP%&
7691 option. Here is an example where two MySQL servers are listed:
7693 hide mysql_servers = localhost/users/root/secret:\
7694 otherhost/users/root/othersecret
7696 For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but
7697 because this is a colon-separated list, the colon has to be doubled. For each
7698 query, these parameter groups are tried in order until a connection is made and
7699 a query is successfully processed. The result of a query may be that no data is
7700 found, but that is still a successful query. In other words, the list of
7701 servers provides a backup facility, not a list of different places to look.
7703 For Redis the global option need not be specified if all queries contain their
7704 own server information &-- see section &<<SECTspeserque>>&.
7705 If specified, the option must be set to a colon-separated list of server
7707 Each item in the list is a slash-separated list of three items:
7708 host, database number, and password.
7710 The host is required and may be either an IPv4 address and optional
7711 port number (separated by a colon, which needs doubling due to the
7712 higher-level list), or a Unix socket pathname enclosed in parentheses
7714 The database number is optional; if present that number is selected in the backend
7716 The password is optional; if present it is used to authenticate to the backend
7719 The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators
7720 convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b
7721 respectively, and the characters single-quote, double-quote, and backslash
7722 itself are escaped with backslashes.
7724 The &%quote_redis%& expansion operator
7725 escapes whitespace and backslash characters with a backslash.
7727 .section "Specifying the server in the query" "SECTspeserque"
7728 For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
7729 it is possible to specify a list of servers with an individual query. This is
7730 done by starting the query with
7732 &`servers=`&&'server1:server2:server3:...'&&`;`&
7734 Each item in the list may take one of two forms:
7736 If it contains no slashes it is assumed to be just a host name. The appropriate
7737 global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host
7738 of the same name, and the remaining parameters (database, user, password) are
7741 If it contains any slashes, it is taken as a complete parameter set.
7743 The list of servers is used in exactly the same way as the global list.
7744 Once a connection to a server has happened and a query has been
7745 successfully executed, processing of the lookup ceases.
7747 This feature is intended for use in master/slave situations where updates
7748 are occurring and you want to update the master rather than a slave. If the
7749 master is in the list as a backup for reading, you might have a global setting
7752 mysql_servers = slave1/db/name/pw:\
7756 In an updating lookup, you could then write:
7758 ${lookup mysql{servers=master; UPDATE ...} }
7760 That query would then be sent only to the master server. If, on the other hand,
7761 the master is not to be used for reading, and so is not present in the global
7762 option, you can still update it by a query of this form:
7764 ${lookup pgsql{servers=master/db/name/pw; UPDATE ...} }
7768 .section "Special MySQL features" "SECID73"
7769 For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%&
7770 causes a connection to the server on the local host by means of a Unix domain
7771 socket. An alternate socket can be specified in parentheses.
7772 An option group name for MySQL option files can be specified in square brackets;
7773 the default value is &"exim"&.
7774 The full syntax of each item in &%mysql_servers%& is:
7776 <&'hostname'&>::<&'port'&>(<&'socket name'&>)[<&'option group'&>]/&&&
7777 <&'database'&>/<&'user'&>/<&'password'&>
7779 Any of the four sub-parts of the first field can be omitted. For normal use on
7780 the local host it can be left blank or set to just &"localhost"&.
7782 No database need be supplied &-- but if it is absent here, it must be given in
7785 If a MySQL query is issued that does not request any data (an insert, update,
7786 or delete command), the result of the lookup is the number of rows affected.
7788 &*Warning*&: This can be misleading. If an update does not actually change
7789 anything (for example, setting a field to the value it already has), the result
7790 is zero because no rows are affected.
7793 .section "Special PostgreSQL features" "SECID74"
7794 PostgreSQL lookups can also use Unix domain socket connections to the database.
7795 This is usually faster and costs less CPU time than a TCP/IP connection.
7796 However it can be used only if the mail server runs on the same machine as the
7797 database server. A configuration line for PostgreSQL via Unix domain sockets
7800 hide pgsql_servers = (/tmp/.s.PGSQL.5432)/db/user/password : ...
7802 In other words, instead of supplying a host name, a path to the socket is
7803 given. The path name is enclosed in parentheses so that its slashes aren't
7804 visually confused with the delimiters for the other server parameters.
7806 If a PostgreSQL query is issued that does not request any data (an insert,
7807 update, or delete command), the result of the lookup is the number of rows
7810 .section "More about SQLite" "SECTsqlite"
7811 .cindex "lookup" "SQLite"
7812 .cindex "sqlite lookup type"
7813 SQLite is different to the other SQL lookups because a file name is required in
7814 addition to the SQL query. An SQLite database is a single file, and there is no
7815 daemon as in the other SQL databases. The interface to Exim requires the name
7816 of the file, as an absolute path, to be given at the start of the query. It is
7817 separated from the query by white space. This means that the path name cannot
7818 contain white space. Here is a lookup expansion example:
7820 ${lookup sqlite {/some/thing/sqlitedb \
7821 select name from aliases where id='userx';}}
7823 In a list, the syntax is similar. For example:
7825 domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \
7826 select * from relays where ip='$sender_host_address';
7828 The only character affected by the &%quote_sqlite%& operator is a single
7829 quote, which it doubles.
7831 .cindex timeout SQLite
7832 .cindex sqlite "lookup timeout"
7833 The SQLite library handles multiple simultaneous accesses to the database
7834 internally. Multiple readers are permitted, but only one process can
7835 update at once. Attempts to access the database while it is being updated
7836 are rejected after a timeout period, during which the SQLite library
7837 waits for the lock to be released. In Exim, the default timeout is set
7838 to 5 seconds, but it can be changed by means of the &%sqlite_lock_timeout%&
7841 .section "More about Redis" "SECTredis"
7842 .cindex "lookup" "Redis"
7843 .cindex "redis lookup type"
7844 Redis is a non-SQL database. Commands are simple get and set.
7847 ${lookup redis{set keyname ${quote_redis:objvalue plus}}}
7848 ${lookup redis{get keyname}}
7851 As of release 4.91, "lightweight" support for Redis Cluster is available.
7852 Requires &%redis_servers%& list to contain all the servers in the cluster, all
7853 of which must be reachable from the running exim instance. If the cluster has
7854 master/slave replication, the list must contain all the master and slave
7857 When the Redis Cluster returns a "MOVED" response to a query, Exim does not
7858 immediately follow the redirection but treats the response as a DEFER, moving on
7859 to the next server in the &%redis_servers%& list until the correct server is
7866 . ////////////////////////////////////////////////////////////////////////////
7867 . ////////////////////////////////////////////////////////////////////////////
7869 .chapter "Domain, host, address, and local part lists" &&&
7870 "CHAPdomhosaddlists" &&&
7871 "Domain, host, and address lists"
7872 .scindex IIDdohoadli "lists of domains; hosts; etc."
7873 A number of Exim configuration options contain lists of domains, hosts,
7874 email addresses, or local parts. For example, the &%hold_domains%& option
7875 contains a list of domains whose delivery is currently suspended. These lists
7876 are also used as data in ACL statements (see chapter &<<CHAPACL>>&), and as
7877 arguments to expansion conditions such as &%match_domain%&.
7879 Each item in one of these lists is a pattern to be matched against a domain,
7880 host, email address, or local part, respectively. In the sections below, the
7881 different types of pattern for each case are described, but first we cover some
7882 general facilities that apply to all four kinds of list.
7884 Note that other parts of Exim use a &'string list'& which does not
7885 support all the complexity available in
7886 domain, host, address and local part lists.
7890 .section "Expansion of lists" "SECTlistexpand"
7891 .cindex "expansion" "of lists"
7892 Each list is expanded as a single string before it is used.
7894 &'Exception: the router headers_remove option, where list-item
7895 splitting is done before string-expansion.'&
7898 expansion must be a list, possibly containing empty items, which is split up
7899 into separate items for matching. By default, colon is the separator character,
7900 but this can be varied if necessary. See sections &<<SECTlistconstruct>>& and
7901 &<<SECTempitelis>>& for details of the list syntax; the second of these
7902 discusses the way to specify empty list items.
7905 If the string expansion is forced to fail, Exim behaves as if the item it is
7906 testing (domain, host, address, or local part) is not in the list. Other
7907 expansion failures cause temporary errors.
7909 If an item in a list is a regular expression, backslashes, dollars and possibly
7910 other special characters in the expression must be protected against
7911 misinterpretation by the string expander. The easiest way to do this is to use
7912 the &`\N`& expansion feature to indicate that the contents of the regular
7913 expression should not be expanded. For example, in an ACL you might have:
7915 deny senders = \N^\d{8}\w@.*\.baddomain\.example$\N : \
7916 ${lookup{$domain}lsearch{/badsenders/bydomain}}
7918 The first item is a regular expression that is protected from expansion by
7919 &`\N`&, whereas the second uses the expansion to obtain a list of unwanted
7920 senders based on the receiving domain.
7925 .section "Negated items in lists" "SECID76"
7926 .cindex "list" "negation"
7927 .cindex "negation" "in lists"
7928 Items in a list may be positive or negative. Negative items are indicated by a
7929 leading exclamation mark, which may be followed by optional white space. A list
7930 defines a set of items (domains, etc). When Exim processes one of these lists,
7931 it is trying to find out whether a domain, host, address, or local part
7932 (respectively) is in the set that is defined by the list. It works like this:
7934 The list is scanned from left to right. If a positive item is matched, the
7935 subject that is being checked is in the set; if a negative item is matched, the
7936 subject is not in the set. If the end of the list is reached without the
7937 subject having matched any of the patterns, it is in the set if the last item
7938 was a negative one, but not if it was a positive one. For example, the list in
7940 domainlist relay_to_domains = !a.b.c : *.b.c
7942 matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match
7943 neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the
7944 list is positive. However, if the setting were
7946 domainlist relay_to_domains = !a.b.c
7948 then all domains other than &'a.b.c'& would match because the last item in the
7949 list is negative. In other words, a list that ends with a negative item behaves
7950 as if it had an extra item &`:*`& on the end.
7952 Another way of thinking about positive and negative items in lists is to read
7953 the connector as &"or"& after a positive item and as &"and"& after a negative
7958 .section "File names in lists" "SECTfilnamlis"
7959 .cindex "list" "file name in"
7960 If an item in a domain, host, address, or local part list is an absolute file
7961 name (beginning with a slash character), each line of the file is read and
7962 processed as if it were an independent item in the list, except that further
7963 file names are not allowed,
7964 and no expansion of the data from the file takes place.
7965 Empty lines in the file are ignored, and the file may also contain comment
7969 For domain and host lists, if a # character appears anywhere in a line of the
7970 file, it and all following characters are ignored.
7972 Because local parts may legitimately contain # characters, a comment in an
7973 address list or local part list file is recognized only if # is preceded by
7974 white space or the start of the line. For example:
7976 not#comment@x.y.z # but this is a comment
7980 Putting a file name in a list has the same effect as inserting each line of the
7981 file as an item in the list (blank lines and comments excepted). However, there
7982 is one important difference: the file is read each time the list is processed,
7983 so if its contents vary over time, Exim's behaviour changes.
7985 If a file name is preceded by an exclamation mark, the sense of any match
7986 within the file is inverted. For example, if
7988 hold_domains = !/etc/nohold-domains
7990 and the file contains the lines
7995 then &'a.b.c'& is in the set of domains defined by &%hold_domains%&, whereas
7996 any domain matching &`*.b.c`& is not.
8000 .section "An lsearch file is not an out-of-line list" "SECID77"
8001 As will be described in the sections that follow, lookups can be used in lists
8002 to provide indexed methods of checking list membership. There has been some
8003 confusion about the way &(lsearch)& lookups work in lists. Because
8004 an &(lsearch)& file contains plain text and is scanned sequentially, it is
8005 sometimes thought that it is allowed to contain wild cards and other kinds of
8006 non-constant pattern. This is not the case. The keys in an &(lsearch)& file are
8007 always fixed strings, just as for any other single-key lookup type.
8009 If you want to use a file to contain wild-card patterns that form part of a
8010 list, just give the file name on its own, without a search type, as described
8011 in the previous section. You could also use the &(wildlsearch)& or
8012 &(nwildlsearch)&, but there is no advantage in doing this.
8017 .section "Named lists" "SECTnamedlists"
8018 .cindex "named lists"
8019 .cindex "list" "named"
8020 A list of domains, hosts, email addresses, or local parts can be given a name
8021 which is then used to refer to the list elsewhere in the configuration. This is
8022 particularly convenient if the same list is required in several different
8023 places. It also allows lists to be given meaningful names, which can improve
8024 the readability of the configuration. For example, it is conventional to define
8025 a domain list called &'local_domains'& for all the domains that are handled
8026 locally on a host, using a configuration line such as
8028 domainlist local_domains = localhost:my.dom.example
8030 Named lists are referenced by giving their name preceded by a plus sign, so,
8031 for example, a router that is intended to handle local domains would be
8032 configured with the line
8034 domains = +local_domains
8036 The first router in a configuration is often one that handles all domains
8037 except the local ones, using a configuration with a negated item like this:
8041 domains = ! +local_domains
8042 transport = remote_smtp
8045 The four kinds of named list are created by configuration lines starting with
8046 the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&,
8047 respectively. Then there follows the name that you are defining, followed by an
8048 equals sign and the list itself. For example:
8050 hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example
8051 addresslist bad_senders = cdb;/etc/badsenders
8053 A named list may refer to other named lists:
8055 domainlist dom1 = first.example : second.example
8056 domainlist dom2 = +dom1 : third.example
8057 domainlist dom3 = fourth.example : +dom2 : fifth.example
8059 &*Warning*&: If the last item in a referenced list is a negative one, the
8060 effect may not be what you intended, because the negation does not propagate
8061 out to the higher level. For example, consider:
8063 domainlist dom1 = !a.b
8064 domainlist dom2 = +dom1 : *.b
8066 The second list specifies &"either in the &%dom1%& list or &'*.b'&"&. The first
8067 list specifies just &"not &'a.b'&"&, so the domain &'x.y'& matches it. That
8068 means it matches the second list as well. The effect is not the same as
8070 domainlist dom2 = !a.b : *.b
8072 where &'x.y'& does not match. It's best to avoid negation altogether in
8073 referenced lists if you can.
8075 Named lists may have a performance advantage. When Exim is routing an
8076 address or checking an incoming message, it caches the result of tests on named
8077 lists. So, if you have a setting such as
8079 domains = +local_domains
8081 on several of your routers
8082 or in several ACL statements,
8083 the actual test is done only for the first one. However, the caching works only
8084 if there are no expansions within the list itself or any sublists that it
8085 references. In other words, caching happens only for lists that are known to be
8086 the same each time they are referenced.
8088 By default, there may be up to 16 named lists of each type. This limit can be
8089 extended by changing a compile-time variable. The use of domain and host lists
8090 is recommended for concepts such as local domains, relay domains, and relay
8091 hosts. The default configuration is set up like this.
8095 .section "Named lists compared with macros" "SECID78"
8096 .cindex "list" "named compared with macro"
8097 .cindex "macro" "compared with named list"
8098 At first sight, named lists might seem to be no different from macros in the
8099 configuration file. However, macros are just textual substitutions. If you
8102 ALIST = host1 : host2
8103 auth_advertise_hosts = !ALIST
8105 it probably won't do what you want, because that is exactly the same as
8107 auth_advertise_hosts = !host1 : host2
8109 Notice that the second host name is not negated. However, if you use a host
8112 hostlist alist = host1 : host2
8113 auth_advertise_hosts = ! +alist
8115 the negation applies to the whole list, and so that is equivalent to
8117 auth_advertise_hosts = !host1 : !host2
8121 .section "Named list caching" "SECID79"
8122 .cindex "list" "caching of named"
8123 .cindex "caching" "named lists"
8124 While processing a message, Exim caches the result of checking a named list if
8125 it is sure that the list is the same each time. In practice, this means that
8126 the cache operates only if the list contains no $ characters, which guarantees
8127 that it will not change when it is expanded. Sometimes, however, you may have
8128 an expanded list that you know will be the same each time within a given
8129 message. For example:
8131 domainlist special_domains = \
8132 ${lookup{$sender_host_address}cdb{/some/file}}
8134 This provides a list of domains that depends only on the sending host's IP
8135 address. If this domain list is referenced a number of times (for example,
8136 in several ACL lines, or in several routers) the result of the check is not
8137 cached by default, because Exim does not know that it is going to be the
8138 same list each time.
8140 By appending &`_cache`& to &`domainlist`& you can tell Exim to go ahead and
8141 cache the result anyway. For example:
8143 domainlist_cache special_domains = ${lookup{...
8145 If you do this, you should be absolutely sure that caching is going to do
8146 the right thing in all cases. When in doubt, leave it out.
8150 .section "Domain lists" "SECTdomainlist"
8151 .cindex "domain list" "patterns for"
8152 .cindex "list" "domain list"
8153 Domain lists contain patterns that are to be matched against a mail domain.
8154 The following types of item may appear in domain lists:
8157 .cindex "primary host name"
8158 .cindex "host name" "matched in domain list"
8159 .oindex "&%primary_hostname%&"
8160 .cindex "domain list" "matching primary host name"
8161 .cindex "@ in a domain list"
8162 If a pattern consists of a single @ character, it matches the local host name,
8163 as set by the &%primary_hostname%& option (or defaulted). This makes it
8164 possible to use the same configuration file on several different hosts that
8165 differ only in their names.
8167 .cindex "@[] in a domain list"
8168 .cindex "domain list" "matching local IP interfaces"
8169 .cindex "domain literal"
8170 If a pattern consists of the string &`@[]`& it matches an IP address enclosed
8171 in square brackets (as in an email address that contains a domain literal), but
8172 only if that IP address is recognized as local for email routing purposes. The
8173 &%local_interfaces%& and &%extra_local_interfaces%& options can be used to
8174 control which of a host's several IP addresses are treated as local.
8175 In today's Internet, the use of domain literals is controversial.
8178 .cindex "@mx_primary"
8179 .cindex "@mx_secondary"
8180 .cindex "domain list" "matching MX pointers to local host"
8181 If a pattern consists of the string &`@mx_any`& it matches any domain that
8182 has an MX record pointing to the local host or to any host that is listed in
8183 .oindex "&%hosts_treat_as_local%&"
8184 &%hosts_treat_as_local%&. The items &`@mx_primary`& and &`@mx_secondary`&
8185 are similar, except that the first matches only when a primary MX target is the
8186 local host, and the second only when no primary MX target is the local host,
8187 but a secondary MX target is. &"Primary"& means an MX record with the lowest
8188 preference value &-- there may of course be more than one of them.
8190 The MX lookup that takes place when matching a pattern of this type is
8191 performed with the resolver options for widening names turned off. Thus, for
8192 example, a single-component domain will &'not'& be expanded by adding the
8193 resolver's default domain. See the &%qualify_single%& and &%search_parents%&
8194 options of the &(dnslookup)& router for a discussion of domain widening.
8196 Sometimes you may want to ignore certain IP addresses when using one of these
8197 patterns. You can specify this by following the pattern with &`/ignore=`&<&'ip
8198 list'&>, where <&'ip list'&> is a list of IP addresses. These addresses are
8199 ignored when processing the pattern (compare the &%ignore_target_hosts%& option
8200 on a router). For example:
8202 domains = @mx_any/ignore=127.0.0.1
8204 This example matches any domain that has an MX record pointing to one of
8205 the local host's IP addresses other than 127.0.0.1.
8207 The list of IP addresses is in fact processed by the same code that processes
8208 host lists, so it may contain CIDR-coded network specifications and it may also
8209 contain negative items.
8211 Because the list of IP addresses is a sublist within a domain list, you have to
8212 be careful about delimiters if there is more than one address. Like any other
8213 list, the default delimiter can be changed. Thus, you might have:
8215 domains = @mx_any/ignore=<;127.0.0.1;0.0.0.0 : \
8216 an.other.domain : ...
8218 so that the sublist uses semicolons for delimiters. When IPv6 addresses are
8219 involved, it is easiest to change the delimiter for the main list as well:
8221 domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
8222 an.other.domain ? ...
8225 .cindex "asterisk" "in domain list"
8226 .cindex "domain list" "asterisk in"
8227 .cindex "domain list" "matching &""ends with""&"
8228 If a pattern starts with an asterisk, the remaining characters of the pattern
8229 are compared with the terminating characters of the domain. The use of &"*"& in
8230 domain lists differs from its use in partial matching lookups. In a domain
8231 list, the character following the asterisk need not be a dot, whereas partial
8232 matching works only in terms of dot-separated components. For example, a domain
8233 list item such as &`*key.ex`& matches &'donkey.ex'& as well as
8237 .cindex "regular expressions" "in domain list"
8238 .cindex "domain list" "matching regular expression"
8239 If a pattern starts with a circumflex character, it is treated as a regular
8240 expression, and matched against the domain using a regular expression matching
8241 function. The circumflex is treated as part of the regular expression.
8242 Email domains are case-independent, so this regular expression match is by
8243 default case-independent, but you can make it case-dependent by starting it
8244 with &`(?-i)`&. References to descriptions of the syntax of regular expressions
8245 are given in chapter &<<CHAPregexp>>&.
8247 &*Warning*&: Because domain lists are expanded before being processed, you
8248 must escape any backslash and dollar characters in the regular expression, or
8249 use the special &`\N`& sequence (see chapter &<<CHAPexpand>>&) to specify that
8250 it is not to be expanded (unless you really do want to build a regular
8251 expression by expansion, of course).
8253 .cindex "lookup" "in domain list"
8254 .cindex "domain list" "matching by lookup"
8255 If a pattern starts with the name of a single-key lookup type followed by a
8256 semicolon (for example, &"dbm;"& or &"lsearch;"&), the remainder of the pattern
8257 must be a file name in a suitable format for the lookup type. For example, for
8258 &"cdb;"& it must be an absolute path:
8260 domains = cdb;/etc/mail/local_domains.cdb
8262 The appropriate type of lookup is done on the file using the domain name as the
8263 key. In most cases, the data that is looked up is not used; Exim is interested
8264 only in whether or not the key is present in the file. However, when a lookup
8265 is used for the &%domains%& option on a router
8266 or a &%domains%& condition in an ACL statement, the data is preserved in the
8267 &$domain_data$& variable and can be referred to in other router options or
8268 other statements in the same ACL.
8271 Any of the single-key lookup type names may be preceded by
8272 &`partial`&<&'n'&>&`-`&, where the <&'n'&> is optional, for example,
8274 domains = partial-dbm;/partial/domains
8276 This causes partial matching logic to be invoked; a description of how this
8277 works is given in section &<<SECTpartiallookup>>&.
8280 .cindex "asterisk" "in lookup type"
8281 Any of the single-key lookup types may be followed by an asterisk. This causes
8282 a default lookup for a key consisting of a single asterisk to be done if the
8283 original lookup fails. This is not a useful feature when using a domain list to
8284 select particular domains (because any domain would match), but it might have
8285 value if the result of the lookup is being used via the &$domain_data$&
8288 If the pattern starts with the name of a query-style lookup type followed by a
8289 semicolon (for example, &"nisplus;"& or &"ldap;"&), the remainder of the
8290 pattern must be an appropriate query for the lookup type, as described in
8291 chapter &<<CHAPfdlookup>>&. For example:
8293 hold_domains = mysql;select domain from holdlist \
8294 where domain = '${quote_mysql:$domain}';
8296 In most cases, the data that is looked up is not used (so for an SQL query, for
8297 example, it doesn't matter what field you select). Exim is interested only in
8298 whether or not the query succeeds. However, when a lookup is used for the
8299 &%domains%& option on a router, the data is preserved in the &$domain_data$&
8300 variable and can be referred to in other options.
8302 .cindex "domain list" "matching literal domain name"
8303 If none of the above cases apply, a caseless textual comparison is made
8304 between the pattern and the domain.
8307 Here is an example that uses several different kinds of pattern:
8309 domainlist funny_domains = \
8312 *.foundation.fict.example : \
8313 \N^[1-2]\d{3}\.fict\.example$\N : \
8314 partial-dbm;/opt/data/penguin/book : \
8315 nis;domains.byname : \
8316 nisplus;[name=$domain,status=local],domains.org_dir
8318 There are obvious processing trade-offs among the various matching modes. Using
8319 an asterisk is faster than a regular expression, and listing a few names
8320 explicitly probably is too. The use of a file or database lookup is expensive,
8321 but may be the only option if hundreds of names are required. Because the
8322 patterns are tested in order, it makes sense to put the most commonly matched
8327 .section "Host lists" "SECThostlist"
8328 .cindex "host list" "patterns in"
8329 .cindex "list" "host list"
8330 Host lists are used to control what remote hosts are allowed to do. For
8331 example, some hosts may be allowed to use the local host as a relay, and some
8332 may be permitted to use the SMTP ETRN command. Hosts can be identified in
8333 two different ways, by name or by IP address. In a host list, some types of
8334 pattern are matched to a host name, and some are matched to an IP address.
8335 You need to be particularly careful with this when single-key lookups are
8336 involved, to ensure that the right value is being used as the key.
8339 .section "Special host list patterns" "SECID80"
8340 .cindex "empty item in hosts list"
8341 .cindex "host list" "empty string in"
8342 If a host list item is the empty string, it matches only when no remote host is
8343 involved. This is the case when a message is being received from a local
8344 process using SMTP on the standard input, that is, when a TCP/IP connection is
8347 .cindex "asterisk" "in host list"
8348 The special pattern &"*"& in a host list matches any host or no host. Neither
8349 the IP address nor the name is actually inspected.
8353 .section "Host list patterns that match by IP address" "SECThoslispatip"
8354 .cindex "host list" "matching IP addresses"
8355 If an IPv4 host calls an IPv6 host and the call is accepted on an IPv6 socket,
8356 the incoming address actually appears in the IPv6 host as
8357 &`::ffff:`&<&'v4address'&>. When such an address is tested against a host
8358 list, it is converted into a traditional IPv4 address first. (Not all operating
8359 systems accept IPv4 calls on IPv6 sockets, as there have been some security
8362 The following types of pattern in a host list check the remote host by
8363 inspecting its IP address:
8366 If the pattern is a plain domain name (not a regular expression, not starting
8367 with *, not a lookup of any kind), Exim calls the operating system function
8368 to find the associated IP address(es). Exim uses the newer
8369 &[getipnodebyname()]& function when available, otherwise &[gethostbyname()]&.
8370 This typically causes a forward DNS lookup of the name. The result is compared
8371 with the IP address of the subject host.
8373 If there is a temporary problem (such as a DNS timeout) with the host name
8374 lookup, a temporary error occurs. For example, if the list is being used in an
8375 ACL condition, the ACL gives a &"defer"& response, usually leading to a
8376 temporary SMTP error code. If no IP address can be found for the host name,
8377 what happens is described in section &<<SECTbehipnot>>& below.
8380 .cindex "@ in a host list"
8381 If the pattern is &"@"&, the primary host name is substituted and used as a
8382 domain name, as just described.
8385 If the pattern is an IP address, it is matched against the IP address of the
8386 subject host. IPv4 addresses are given in the normal &"dotted-quad"& notation.
8387 IPv6 addresses can be given in colon-separated format, but the colons have to
8388 be doubled so as not to be taken as item separators when the default list
8389 separator is used. IPv6 addresses are recognized even when Exim is compiled
8390 without IPv6 support. This means that if they appear in a host list on an
8391 IPv4-only host, Exim will not treat them as host names. They are just addresses
8392 that can never match a client host.
8395 .cindex "@[] in a host list"
8396 If the pattern is &"@[]"&, it matches the IP address of any IP interface on
8397 the local host. For example, if the local host is an IPv4 host with one
8398 interface address 10.45.23.56, these two ACL statements have the same effect:
8400 accept hosts = 127.0.0.1 : 10.45.23.56
8404 .cindex "CIDR notation"
8405 If the pattern is an IP address followed by a slash and a mask length (for
8406 example 10.11.42.0/24), it is matched against the IP address of the subject
8407 host under the given mask. This allows, an entire network of hosts to be
8408 included (or excluded) by a single item. The mask uses CIDR notation; it
8409 specifies the number of address bits that must match, starting from the most
8410 significant end of the address.
8412 &*Note*&: The mask is &'not'& a count of addresses, nor is it the high number
8413 of a range of addresses. It is the number of bits in the network portion of the
8414 address. The above example specifies a 24-bit netmask, so it matches all 256
8415 addresses in the 10.11.42.0 network. An item such as
8419 matches just two addresses, 192.168.23.236 and 192.168.23.237. A mask value of
8420 32 for an IPv4 address is the same as no mask at all; just a single address
8423 Here is another example which shows an IPv4 and an IPv6 network:
8425 recipient_unqualified_hosts = 192.168.0.0/16: \
8426 3ffe::ffff::836f::::/48
8428 The doubling of list separator characters applies only when these items
8429 appear inline in a host list. It is not required when indirecting via a file.
8432 recipient_unqualified_hosts = /opt/exim/unqualnets
8434 could make use of a file containing
8439 to have exactly the same effect as the previous example. When listing IPv6
8440 addresses inline, it is usually more convenient to use the facility for
8441 changing separator characters. This list contains the same two networks:
8443 recipient_unqualified_hosts = <; 172.16.0.0/12; \
8446 The separator is changed to semicolon by the leading &"<;"& at the start of the
8452 .section "Host list patterns for single-key lookups by host address" &&&
8453 "SECThoslispatsikey"
8454 .cindex "host list" "lookup of IP address"
8455 When a host is to be identified by a single-key lookup of its complete IP
8456 address, the pattern takes this form:
8458 &`net-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8462 hosts_lookup = net-cdb;/hosts-by-ip.db
8464 The text form of the IP address of the subject host is used as the lookup key.
8465 IPv6 addresses are converted to an unabbreviated form, using lower case
8466 letters, with dots as separators because colon is the key terminator in
8467 &(lsearch)& files. [Colons can in fact be used in keys in &(lsearch)& files by
8468 quoting the keys, but this is a facility that was added later.] The data
8469 returned by the lookup is not used.
8471 .cindex "IP address" "masking"
8472 .cindex "host list" "masked IP address"
8473 Single-key lookups can also be performed using masked IP addresses, using
8474 patterns of this form:
8476 &`net<`&&'number'&&`>-<`&&'single-key-search-type'&&`>;<`&&'search-data'&&`>`&
8480 net24-dbm;/networks.db
8482 The IP address of the subject host is masked using <&'number'&> as the mask
8483 length. A textual string is constructed from the masked value, followed by the
8484 mask, and this is used as the lookup key. For example, if the host's IP address
8485 is 192.168.34.6, the key that is looked up for the above example is
8486 &"192.168.34.0/24"&.
8488 When an IPv6 address is converted to a string, dots are normally used instead
8489 of colons, so that keys in &(lsearch)& files need not contain colons (which
8490 terminate &(lsearch)& keys). This was implemented some time before the ability
8491 to quote keys was made available in &(lsearch)& files. However, the more
8492 recently implemented &(iplsearch)& files do require colons in IPv6 keys
8493 (notated using the quoting facility) so as to distinguish them from IPv4 keys.
8494 For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are
8495 converted using colons and not dots. In all cases, full, unabbreviated IPv6
8496 addresses are always used.
8498 Ideally, it would be nice to tidy up this anomalous situation by changing to
8499 colons in all cases, given that quoting is now available for &(lsearch)&.
8500 However, this would be an incompatible change that might break some existing
8503 &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an
8504 IPv6 address) is not the same as specifying just &%net-%& without a number. In
8505 the former case the key strings include the mask value, whereas in the latter
8506 case the IP address is used on its own.
8510 .section "Host list patterns that match by host name" "SECThoslispatnam"
8511 .cindex "host" "lookup failures"
8512 .cindex "unknown host name"
8513 .cindex "host list" "matching host name"
8514 There are several types of pattern that require Exim to know the name of the
8515 remote host. These are either wildcard patterns or lookups by name. (If a
8516 complete hostname is given without any wildcarding, it is used to find an IP
8517 address to match against, as described in section &<<SECThoslispatip>>&
8520 If the remote host name is not already known when Exim encounters one of these
8521 patterns, it has to be found from the IP address.
8522 Although many sites on the Internet are conscientious about maintaining reverse
8523 DNS data for their hosts, there are also many that do not do this.
8524 Consequently, a name cannot always be found, and this may lead to unwanted
8525 effects. Take care when configuring host lists with wildcarded name patterns.
8526 Consider what will happen if a name cannot be found.
8528 Because of the problems of determining host names from IP addresses, matching
8529 against host names is not as common as matching against IP addresses.
8531 By default, in order to find a host name, Exim first does a reverse DNS lookup;
8532 if no name is found in the DNS, the system function (&[gethostbyaddr()]& or
8533 &[getipnodebyaddr()]& if available) is tried. The order in which these lookups
8534 are done can be changed by setting the &%host_lookup_order%& option. For
8535 security, once Exim has found one or more names, it looks up the IP addresses
8536 for these names and compares them with the IP address that it started with.
8537 Only those names whose IP addresses match are accepted. Any other names are
8538 discarded. If no names are left, Exim behaves as if the host name cannot be
8539 found. In the most common case there is only one name and one IP address.
8541 There are some options that control what happens if a host name cannot be
8542 found. These are described in section &<<SECTbehipnot>>& below.
8544 .cindex "host" "alias for"
8545 .cindex "alias for host"
8546 As a result of aliasing, hosts may have more than one name. When processing any
8547 of the following types of pattern, all the host's names are checked:
8550 .cindex "asterisk" "in host list"
8551 If a pattern starts with &"*"& the remainder of the item must match the end of
8552 the host name. For example, &`*.b.c`& matches all hosts whose names end in
8553 &'.b.c'&. This special simple form is provided because this is a very common
8554 requirement. Other kinds of wildcarding require the use of a regular
8557 .cindex "regular expressions" "in host list"
8558 .cindex "host list" "regular expression in"
8559 If the item starts with &"^"& it is taken to be a regular expression which is
8560 matched against the host name. Host names are case-independent, so this regular
8561 expression match is by default case-independent, but you can make it
8562 case-dependent by starting it with &`(?-i)`&. References to descriptions of the
8563 syntax of regular expressions are given in chapter &<<CHAPregexp>>&. For
8568 is a regular expression that matches either of the two hosts &'a.c.d'& or
8569 &'b.c.d'&. When a regular expression is used in a host list, you must take care
8570 that backslash and dollar characters are not misinterpreted as part of the
8571 string expansion. The simplest way to do this is to use &`\N`& to mark that
8572 part of the string as non-expandable. For example:
8574 sender_unqualified_hosts = \N^(a|b)\.c\.d$\N : ....
8576 &*Warning*&: If you want to match a complete host name, you must include the
8577 &`$`& terminating metacharacter in the regular expression, as in the above
8578 example. Without it, a match at the start of the host name is all that is
8585 .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot"
8586 .cindex "host" "lookup failures, permanent"
8587 While processing a host list, Exim may need to look up an IP address from a
8588 name (see section &<<SECThoslispatip>>&), or it may need to look up a host name
8589 from an IP address (see section &<<SECThoslispatnam>>&). In either case, the
8590 behaviour when it fails to find the information it is seeking is the same.
8592 &*Note*&: This section applies to permanent lookup failures. It does &'not'&
8593 apply to temporary DNS errors, whose handling is described in the next section.
8595 .cindex "&`+include_unknown`&"
8596 .cindex "&`+ignore_unknown`&"
8597 Exim parses a host list from left to right. If it encounters a permanent
8598 lookup failure in any item in the host list before it has found a match,
8599 Exim treats it as a failure and the default behavior is as if the host
8600 does not match the list. This may not always be what you want to happen.
8601 To change Exim's behaviour, the special items &`+include_unknown`& or
8602 &`+ignore_unknown`& may appear in the list (at top level &-- they are
8603 not recognized in an indirected file).
8606 If any item that follows &`+include_unknown`& requires information that
8607 cannot found, Exim behaves as if the host does match the list. For example,
8609 host_reject_connection = +include_unknown:*.enemy.ex
8611 rejects connections from any host whose name matches &`*.enemy.ex`&, and also
8612 any hosts whose name it cannot find.
8615 If any item that follows &`+ignore_unknown`& requires information that cannot
8616 be found, Exim ignores that item and proceeds to the rest of the list. For
8619 accept hosts = +ignore_unknown : friend.example : \
8622 accepts from any host whose name is &'friend.example'& and from 192.168.4.5,
8623 whether or not its host name can be found. Without &`+ignore_unknown`&, if no
8624 name can be found for 192.168.4.5, it is rejected.
8627 Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same
8628 list. The effect of each one lasts until the next, or until the end of the
8631 .section "Mixing wildcarded host names and addresses in host lists" &&&
8633 .cindex "host list" "mixing names and addresses in"
8635 This section explains the host/ip processing logic with the same concepts
8636 as the previous section, but specifically addresses what happens when a
8637 wildcarded hostname is one of the items in the hostlist.
8640 If you have name lookups or wildcarded host names and
8641 IP addresses in the same host list, you should normally put the IP
8642 addresses first. For example, in an ACL you could have:
8644 accept hosts = 10.9.8.7 : *.friend.example
8646 The reason you normally would order it this way lies in the
8647 left-to-right way that Exim processes lists. It can test IP addresses
8648 without doing any DNS lookups, but when it reaches an item that requires
8649 a host name, it fails if it cannot find a host name to compare with the
8650 pattern. If the above list is given in the opposite order, the
8651 &%accept%& statement fails for a host whose name cannot be found, even
8652 if its IP address is 10.9.8.7.
8655 If you really do want to do the name check first, and still recognize the IP
8656 address, you can rewrite the ACL like this:
8658 accept hosts = *.friend.example
8659 accept hosts = 10.9.8.7
8661 If the first &%accept%& fails, Exim goes on to try the second one. See chapter
8662 &<<CHAPACL>>& for details of ACLs. Alternatively, you can use
8663 &`+ignore_unknown`&, which was discussed in depth in the first example in
8668 .section "Temporary DNS errors when looking up host information" &&&
8670 .cindex "host" "lookup failures, temporary"
8671 .cindex "&`+include_defer`&"
8672 .cindex "&`+ignore_defer`&"
8673 A temporary DNS lookup failure normally causes a defer action (except when
8674 &%dns_again_means_nonexist%& converts it into a permanent error). However,
8675 host lists can include &`+ignore_defer`& and &`+include_defer`&, analogous to
8676 &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous
8677 section. These options should be used with care, probably only in non-critical
8678 host lists such as whitelists.
8682 .section "Host list patterns for single-key lookups by host name" &&&
8683 "SECThoslispatnamsk"
8684 .cindex "unknown host name"
8685 .cindex "host list" "matching host name"
8686 If a pattern is of the form
8688 <&'single-key-search-type'&>;<&'search-data'&>
8692 dbm;/host/accept/list
8694 a single-key lookup is performed, using the host name as its key. If the
8695 lookup succeeds, the host matches the item. The actual data that is looked up
8698 &*Reminder*&: With this kind of pattern, you must have host &'names'& as
8699 keys in the file, not IP addresses. If you want to do lookups based on IP
8700 addresses, you must precede the search type with &"net-"& (see section
8701 &<<SECThoslispatsikey>>&). There is, however, no reason why you could not use
8702 two items in the same list, one doing an address lookup and one doing a name
8703 lookup, both using the same file.
8707 .section "Host list patterns for query-style lookups" "SECID81"
8708 If a pattern is of the form
8710 <&'query-style-search-type'&>;<&'query'&>
8712 the query is obeyed, and if it succeeds, the host matches the item. The actual
8713 data that is looked up is not used. The variables &$sender_host_address$& and
8714 &$sender_host_name$& can be used in the query. For example:
8716 hosts_lookup = pgsql;\
8717 select ip from hostlist where ip='$sender_host_address'
8719 The value of &$sender_host_address$& for an IPv6 address contains colons. You
8720 can use the &%sg%& expansion item to change this if you need to. If you want to
8721 use masked IP addresses in database queries, you can use the &%mask%& expansion
8724 If the query contains a reference to &$sender_host_name$&, Exim automatically
8725 looks up the host name if it has not already done so. (See section
8726 &<<SECThoslispatnam>>& for comments on finding host names.)
8728 Historical note: prior to release 4.30, Exim would always attempt to find a
8729 host name before running the query, unless the search type was preceded by
8730 &`net-`&. This is no longer the case. For backwards compatibility, &`net-`& is
8731 still recognized for query-style lookups, but its presence or absence has no
8732 effect. (Of course, for single-key lookups, &`net-`& &'is'& important.
8733 See section &<<SECThoslispatsikey>>&.)
8739 .section "Address lists" "SECTaddresslist"
8740 .cindex "list" "address list"
8741 .cindex "address list" "empty item"
8742 .cindex "address list" "patterns"
8743 Address lists contain patterns that are matched against mail addresses. There
8744 is one special case to be considered: the sender address of a bounce message is
8745 always empty. You can test for this by providing an empty item in an address
8746 list. For example, you can set up a router to process bounce messages by
8747 using this option setting:
8751 The presence of the colon creates an empty item. If you do not provide any
8752 data, the list is empty and matches nothing. The empty sender can also be
8753 detected by a regular expression that matches an empty string,
8754 and by a query-style lookup that succeeds when &$sender_address$& is empty.
8756 Non-empty items in an address list can be straightforward email addresses. For
8759 senders = jbc@askone.example : hs@anacreon.example
8761 A certain amount of wildcarding is permitted. If a pattern contains an @
8762 character, but is not a regular expression and does not begin with a
8763 semicolon-terminated lookup type (described below), the local part of the
8764 subject address is compared with the local part of the pattern, which may start
8765 with an asterisk. If the local parts match, the domain is checked in exactly
8766 the same way as for a pattern in a domain list. For example, the domain can be
8767 wildcarded, refer to a named list, or be a lookup:
8769 deny senders = *@*.spamming.site:\
8770 *@+hostile_domains:\
8771 bozo@partial-lsearch;/list/of/dodgy/sites:\
8772 *@dbm;/bad/domains.db
8774 .cindex "local part" "starting with !"
8775 .cindex "address list" "local part starting with !"
8776 If a local part that begins with an exclamation mark is required, it has to be
8777 specified using a regular expression, because otherwise the exclamation mark is
8778 treated as a sign of negation, as is standard in lists.
8780 If a non-empty pattern that is not a regular expression or a lookup does not
8781 contain an @ character, it is matched against the domain part of the subject
8782 address. The only two formats that are recognized this way are a literal
8783 domain, or a domain pattern that starts with *. In both these cases, the effect
8784 is the same as if &`*@`& preceded the pattern. For example:
8786 deny senders = enemy.domain : *.enemy.domain
8789 The following kinds of more complicated address list pattern can match any
8790 address, including the empty address that is characteristic of bounce message
8794 .cindex "regular expressions" "in address list"
8795 .cindex "address list" "regular expression in"
8796 If (after expansion) a pattern starts with &"^"&, a regular expression match is
8797 done against the complete address, with the pattern as the regular expression.
8798 You must take care that backslash and dollar characters are not misinterpreted
8799 as part of the string expansion. The simplest way to do this is to use &`\N`&
8800 to mark that part of the string as non-expandable. For example:
8802 deny senders = \N^.*this.*@example\.com$\N : \
8803 \N^\d{8}.+@spamhaus.example$\N : ...
8805 The &`\N`& sequences are removed by the expansion, so these items do indeed
8806 start with &"^"& by the time they are being interpreted as address patterns.
8809 .cindex "address list" "lookup for complete address"
8810 Complete addresses can be looked up by using a pattern that starts with a
8811 lookup type terminated by a semicolon, followed by the data for the lookup. For
8814 deny senders = cdb;/etc/blocked.senders : \
8815 mysql;select address from blocked where \
8816 address='${quote_mysql:$sender_address}'
8818 Both query-style and single-key lookup types can be used. For a single-key
8819 lookup type, Exim uses the complete address as the key. However, empty keys are
8820 not supported for single-key lookups, so a match against the empty address
8821 always fails. This restriction does not apply to query-style lookups.
8823 Partial matching for single-key lookups (section &<<SECTpartiallookup>>&)
8824 cannot be used, and is ignored if specified, with an entry being written to the
8826 .cindex "*@ with single-key lookup"
8827 However, you can configure lookup defaults, as described in section
8828 &<<SECTdefaultvaluelookups>>&, but this is useful only for the &"*@"& type of
8829 default. For example, with this lookup:
8831 accept senders = lsearch*@;/some/file
8833 the file could contains lines like this:
8835 user1@domain1.example
8838 and for the sender address &'nimrod@jaeger.example'&, the sequence of keys
8841 nimrod@jaeger.example
8845 &*Warning 1*&: Do not include a line keyed by &"*"& in the file, because that
8846 would mean that every address matches, thus rendering the test useless.
8848 &*Warning 2*&: Do not confuse these two kinds of item:
8850 deny recipients = dbm*@;/some/file
8851 deny recipients = *@dbm;/some/file
8853 The first does a whole address lookup, with defaulting, as just described,
8854 because it starts with a lookup type. The second matches the local part and
8855 domain independently, as described in a bullet point below.
8859 The following kinds of address list pattern can match only non-empty addresses.
8860 If the subject address is empty, a match against any of these pattern types
8865 .cindex "@@ with single-key lookup"
8866 .cindex "address list" "@@ lookup type"
8867 .cindex "address list" "split local part and domain"
8868 If a pattern starts with &"@@"& followed by a single-key lookup item
8869 (for example, &`@@lsearch;/some/file`&), the address that is being checked is
8870 split into a local part and a domain. The domain is looked up in the file. If
8871 it is not found, there is no match. If it is found, the data that is looked up
8872 from the file is treated as a colon-separated list of local part patterns, each
8873 of which is matched against the subject local part in turn.
8875 .cindex "asterisk" "in address list"
8876 The lookup may be a partial one, and/or one involving a search for a default
8877 keyed by &"*"& (see section &<<SECTdefaultvaluelookups>>&). The local part
8878 patterns that are looked up can be regular expressions or begin with &"*"&, or
8879 even be further lookups. They may also be independently negated. For example,
8882 deny senders = @@dbm;/etc/reject-by-domain
8884 the data from which the DBM file is built could contain lines like
8886 baddomain.com: !postmaster : *
8888 to reject all senders except &%postmaster%& from that domain.
8890 .cindex "local part" "starting with !"
8891 If a local part that actually begins with an exclamation mark is required, it
8892 has to be specified using a regular expression. In &(lsearch)& files, an entry
8893 may be split over several lines by indenting the second and subsequent lines,
8894 but the separating colon must still be included at line breaks. White space
8895 surrounding the colons is ignored. For example:
8897 aol.com: spammer1 : spammer2 : ^[0-9]+$ :
8900 As in all colon-separated lists in Exim, a colon can be included in an item by
8903 If the last item in the list starts with a right angle-bracket, the remainder
8904 of the item is taken as a new key to look up in order to obtain a continuation
8905 list of local parts. The new key can be any sequence of characters. Thus one
8906 might have entries like
8908 aol.com: spammer1 : spammer 2 : >*
8909 xyz.com: spammer3 : >*
8912 in a file that was searched with &%@@dbm*%&, to specify a match for 8-digit
8913 local parts for all domains, in addition to the specific local parts listed for
8914 each domain. Of course, using this feature costs another lookup each time a
8915 chain is followed, but the effort needed to maintain the data is reduced.
8917 .cindex "loop" "in lookups"
8918 It is possible to construct loops using this facility, and in order to catch
8919 them, the chains may be no more than fifty items long.
8922 The @@<&'lookup'&> style of item can also be used with a query-style
8923 lookup, but in this case, the chaining facility is not available. The lookup
8924 can only return a single list of local parts.
8927 &*Warning*&: There is an important difference between the address list items
8928 in these two examples:
8931 senders = *@+my_list
8933 In the first one, &`my_list`& is a named address list, whereas in the second
8934 example it is a named domain list.
8939 .section "Case of letters in address lists" "SECTcasletadd"
8940 .cindex "case of local parts"
8941 .cindex "address list" "case forcing"
8942 .cindex "case forcing in address lists"
8943 Domains in email addresses are always handled caselessly, but for local parts
8944 case may be significant on some systems (see &%caseful_local_part%& for how
8945 Exim deals with this when routing addresses). However, RFC 2505 (&'Anti-Spam
8946 Recommendations for SMTP MTAs'&) suggests that matching of addresses to
8947 blocking lists should be done in a case-independent manner. Since most address
8948 lists in Exim are used for this kind of control, Exim attempts to do this by
8951 The domain portion of an address is always lowercased before matching it to an
8952 address list. The local part is lowercased by default, and any string
8953 comparisons that take place are done caselessly. This means that the data in
8954 the address list itself, in files included as plain file names, and in any file
8955 that is looked up using the &"@@"& mechanism, can be in any case. However, the
8956 keys in files that are looked up by a search type other than &(lsearch)& (which
8957 works caselessly) must be in lower case, because these lookups are not
8960 .cindex "&`+caseful`&"
8961 To allow for the possibility of caseful address list matching, if an item in
8962 an address list is the string &"+caseful"&, the original case of the local
8963 part is restored for any comparisons that follow, and string comparisons are no
8964 longer case-independent. This does not affect the domain, which remains in
8965 lower case. However, although independent matches on the domain alone are still
8966 performed caselessly, regular expressions that match against an entire address
8967 become case-sensitive after &"+caseful"& has been seen.
8971 .section "Local part lists" "SECTlocparlis"
8972 .cindex "list" "local part list"
8973 .cindex "local part" "list"
8974 Case-sensitivity in local part lists is handled in the same way as for address
8975 lists, as just described. The &"+caseful"& item can be used if required. In a
8976 setting of the &%local_parts%& option in a router with &%caseful_local_part%&
8977 set false, the subject is lowercased and the matching is initially
8978 case-insensitive. In this case, &"+caseful"& will restore case-sensitive
8979 matching in the local part list, but not elsewhere in the router. If
8980 &%caseful_local_part%& is set true in a router, matching in the &%local_parts%&
8981 option is case-sensitive from the start.
8983 If a local part list is indirected to a file (see section &<<SECTfilnamlis>>&),
8984 comments are handled in the same way as address lists &-- they are recognized
8985 only if the # is preceded by white space or the start of the line.
8986 Otherwise, local part lists are matched in the same way as domain lists, except
8987 that the special items that refer to the local host (&`@`&, &`@[]`&,
8988 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`&) are not recognized.
8989 Refer to section &<<SECTdomainlist>>& for details of the other available item
8991 .ecindex IIDdohoadli
8996 . ////////////////////////////////////////////////////////////////////////////
8997 . ////////////////////////////////////////////////////////////////////////////
8999 .chapter "String expansions" "CHAPexpand"
9000 .scindex IIDstrexp "expansion" "of strings"
9001 Many strings in Exim's run time configuration are expanded before use. Some of
9002 them are expanded every time they are used; others are expanded only once.
9004 When a string is being expanded it is copied verbatim from left to right except
9005 when a dollar or backslash character is encountered. A dollar specifies the
9006 start of a portion of the string that is interpreted and replaced as described
9007 below in section &<<SECTexpansionitems>>& onwards. Backslash is used as an
9008 escape character, as described in the following section.
9010 Whether a string is expanded depends upon the context. Usually this is solely
9011 dependent upon the option for which a value is sought; in this documentation,
9012 options for which string expansion is performed are marked with † after
9013 the data type. ACL rules always expand strings. A couple of expansion
9014 conditions do not expand some of the brace-delimited branches, for security
9019 .section "Literal text in expanded strings" "SECTlittext"
9020 .cindex "expansion" "including literal text"
9021 An uninterpreted dollar can be included in an expanded string by putting a
9022 backslash in front of it. A backslash can be used to prevent any special
9023 character being treated specially in an expansion, including backslash itself.
9024 If the string appears in quotes in the configuration file, two backslashes are
9025 required because the quotes themselves cause interpretation of backslashes when
9026 the string is read in (see section &<<SECTstrings>>&).
9028 .cindex "expansion" "non-expandable substrings"
9029 A portion of the string can specified as non-expandable by placing it between
9030 two occurrences of &`\N`&. This is particularly useful for protecting regular
9031 expressions, which often contain backslashes and dollar signs. For example:
9033 deny senders = \N^\d{8}[a-z]@some\.site\.example$\N
9035 On encountering the first &`\N`&, the expander copies subsequent characters
9036 without interpretation until it reaches the next &`\N`& or the end of the
9041 .section "Character escape sequences in expanded strings" "SECID82"
9042 .cindex "expansion" "escape sequences"
9043 A backslash followed by one of the letters &"n"&, &"r"&, or &"t"& in an
9044 expanded string is recognized as an escape sequence for the character newline,
9045 carriage return, or tab, respectively. A backslash followed by up to three
9046 octal digits is recognized as an octal encoding for a single character, and a
9047 backslash followed by &"x"& and up to two hexadecimal digits is a hexadecimal
9050 These escape sequences are also recognized in quoted strings when they are read
9051 in. Their interpretation in expansions as well is useful for unquoted strings,
9052 and for other cases such as looked-up strings that are then expanded.
9055 .section "Testing string expansions" "SECID83"
9056 .cindex "expansion" "testing"
9057 .cindex "testing" "string expansion"
9059 Many expansions can be tested by calling Exim with the &%-be%& option. This
9060 takes the command arguments, or lines from the standard input if there are no
9061 arguments, runs them through the string expansion code, and writes the results
9062 to the standard output. Variables based on configuration values are set up, but
9063 since no message is being processed, variables such as &$local_part$& have no
9064 value. Nevertheless the &%-be%& option can be useful for checking out file and
9065 database lookups, and the use of expansion operators such as &%sg%&, &%substr%&
9068 Exim gives up its root privilege when it is called with the &%-be%& option, and
9069 instead runs under the uid and gid it was called with, to prevent users from
9070 using &%-be%& for reading files to which they do not have access.
9073 If you want to test expansions that include variables whose values are taken
9074 from a message, there are two other options that can be used. The &%-bem%&
9075 option is like &%-be%& except that it is followed by a file name. The file is
9076 read as a message before doing the test expansions. For example:
9078 exim -bem /tmp/test.message '$h_subject:'
9080 The &%-Mset%& option is used in conjunction with &%-be%& and is followed by an
9081 Exim message identifier. For example:
9083 exim -be -Mset 1GrA8W-0004WS-LQ '$recipients'
9085 This loads the message from Exim's spool before doing the test expansions, and
9086 is therefore restricted to admin users.
9089 .section "Forced expansion failure" "SECTforexpfai"
9090 .cindex "expansion" "forced failure"
9091 A number of expansions that are described in the following section have
9092 alternative &"true"& and &"false"& substrings, enclosed in brace characters
9093 (which are sometimes called &"curly brackets"&). Which of the two strings is
9094 used depends on some condition that is evaluated as part of the expansion. If,
9095 instead of a &"false"& substring, the word &"fail"& is used (not in braces),
9096 the entire string expansion fails in a way that can be detected by the code
9097 that requested the expansion. This is called &"forced expansion failure"&, and
9098 its consequences depend on the circumstances. In some cases it is no different
9099 from any other expansion failure, but in others a different action may be
9100 taken. Such variations are mentioned in the documentation of the option that is
9106 .section "Expansion items" "SECTexpansionitems"
9107 The following items are recognized in expanded strings. White space may be used
9108 between sub-items that are keywords or substrings enclosed in braces inside an
9109 outer set of braces, to improve readability. &*Warning*&: Within braces,
9110 white space is significant.
9113 .vitem &*$*&<&'variable&~name'&>&~or&~&*${*&<&'variable&~name'&>&*}*&
9114 .cindex "expansion" "variables"
9115 Substitute the contents of the named variable, for example:
9120 The second form can be used to separate the name from subsequent alphanumeric
9121 characters. This form (using braces) is available only for variables; it does
9122 &'not'& apply to message headers. The names of the variables are given in
9123 section &<<SECTexpvar>>& below. If the name of a non-existent variable is
9124 given, the expansion fails.
9126 .vitem &*${*&<&'op'&>&*:*&<&'string'&>&*}*&
9127 .cindex "expansion" "operators"
9128 The string is first itself expanded, and then the operation specified by
9129 <&'op'&> is applied to it. For example:
9133 The string starts with the first character after the colon, which may be
9134 leading white space. A list of operators is given in section &<<SECTexpop>>&
9135 below. The operator notation is used for simple expansion items that have just
9136 one argument, because it reduces the number of braces and therefore makes the
9137 string easier to understand.
9139 .vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*&
9140 This item inserts &"basic"& header lines. It is described with the &%header%&
9141 expansion item below.
9144 .vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&"
9145 .cindex "expansion" "calling an acl"
9146 .cindex "&%acl%&" "call from expansion"
9147 The name and zero to nine argument strings are first expanded separately. The expanded
9148 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
9149 Any unused are made empty. The variable &$acl_narg$& is set to the number of
9150 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
9151 and may use the variables; if another acl expansion is used the values
9152 are restored after it returns. If the ACL sets
9153 a value using a "message =" modifier and returns accept or deny, the value becomes
9154 the result of the expansion.
9155 If no message is set and the ACL returns accept or deny
9156 the expansion result is an empty string.
9157 If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails.
9160 .vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
9161 .cindex authentication "results header"
9162 .cindex headers "authentication-results:"
9163 .cindex authentication "expansion item"
9164 This item returns a string suitable for insertion as an
9165 &'Authentication-Results"'&
9167 The given <&'authserv-id'&> is included in the result; typically this
9168 will be a domain name identifying the system performing the authentications.
9169 Methods that might be present in the result include:
9178 Example use (as an ACL modifier):
9180 add_header = :at_start:${authresults {$primary_hostname}}
9182 This is safe even if no authentication results are available.
9185 .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&&
9186 {*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9187 .cindex "expansion" "extracting certificate fields"
9188 .cindex "&%certextract%&" "certificate fields"
9189 .cindex "certificate" "extracting fields"
9190 The <&'certificate'&> must be a variable of type certificate.
9191 The field name is expanded and used to retrieve the relevant field from
9192 the certificate. Supported fields are:
9196 &`subject `& RFC4514 DN
9197 &`issuer `& RFC4514 DN
9202 &`subj_altname `& tagged list
9206 If the field is found,
9207 <&'string2'&> is expanded, and replaces the whole item;
9208 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9209 variable &$value$& contains the value that has been extracted. Afterwards, it
9210 is restored to any previous value it might have had.
9212 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9213 key is not found. If {<&'string2'&>} is also omitted, the value that was
9216 Some field names take optional modifiers, appended and separated by commas.
9218 The field selectors marked as "RFC4514" above
9219 output a Distinguished Name string which is
9221 parseable by Exim as a comma-separated tagged list
9222 (the exceptions being elements containing commas).
9223 RDN elements of a single type may be selected by
9224 a modifier of the type label; if so the expansion
9225 result is a list (newline-separated by default).
9226 The separator may be changed by another modifier of
9227 a right angle-bracket followed immediately by the new separator.
9228 Recognised RDN type labels include "CN", "O", "OU" and "DC".
9230 The field selectors marked as "time" above
9231 take an optional modifier of "int"
9232 for which the result is the number of seconds since epoch.
9233 Otherwise the result is a human-readable string
9234 in the timezone selected by the main "timezone" option.
9236 The field selectors marked as "list" above return a list,
9237 newline-separated by default,
9238 (embedded separator characters in elements are doubled).
9239 The separator may be changed by a modifier of
9240 a right angle-bracket followed immediately by the new separator.
9242 The field selectors marked as "tagged" above
9243 prefix each list element with a type string and an equals sign.
9244 Elements of only one type may be selected by a modifier
9245 which is one of "dns", "uri" or "mail";
9246 if so the element tags are omitted.
9248 If not otherwise noted field values are presented in human-readable form.
9250 .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&&
9251 {*&<&'arg'&>&*}...}*&"
9253 This expansion dynamically loads and then calls a locally-written C function.
9254 This functionality is available only if Exim is compiled with
9258 set in &_Local/Makefile_&. Once loaded, Exim remembers the dynamically loaded
9259 object so that it doesn't reload the same object file in the same Exim process
9260 (but of course Exim does start new processes frequently).
9262 There may be from zero to eight arguments to the function. When compiling
9263 a local function that is to be called in this way, &_local_scan.h_& should be
9264 included. The Exim variables and functions that are defined by that API
9265 are also available for dynamically loaded functions. The function itself
9266 must have the following type:
9268 int dlfunction(uschar **yield, int argc, uschar *argv[])
9270 Where &`uschar`& is a typedef for &`unsigned char`& in &_local_scan.h_&. The
9271 function should return one of the following values:
9273 &`OK`&: Success. The string that is placed in the variable &'yield'& is put
9274 into the expanded string that is being built.
9276 &`FAIL`&: A non-forced expansion failure occurs, with the error message taken
9277 from &'yield'&, if it is set.
9279 &`FAIL_FORCED`&: A forced expansion failure occurs, with the error message
9280 taken from &'yield'& if it is set.
9282 &`ERROR`&: Same as &`FAIL`&, except that a panic log entry is written.
9284 When compiling a function that is to be used in this way with gcc,
9285 you need to add &%-shared%& to the gcc command. Also, in the Exim build-time
9286 configuration, you must add &%-export-dynamic%& to EXTRALIBS.
9289 .vitem "&*${env{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&"
9290 .cindex "expansion" "extracting value from environment"
9291 .cindex "environment" "values from"
9292 The key is first expanded separately, and leading and trailing white space
9294 This is then searched for as a name in the environment.
9295 If a variable is found then its value is placed in &$value$&
9296 and <&'string1'&> is expanded, otherwise <&'string2'&> is expanded.
9298 Instead of {<&'string2'&>} the word &"fail"& (not in curly brackets) can
9299 appear, for example:
9301 ${env{USER}{$value} fail }
9303 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9304 {<&'string1'&>} must be present for &"fail"& to be recognized.
9306 If {<&'string2'&>} is omitted an empty string is substituted on
9308 If {<&'string1'&>} is omitted the search result is substituted on
9311 The environment is adjusted by the &%keep_environment%& and
9312 &%add_environment%& main section options.
9315 .vitem "&*${extract{*&<&'key'&>&*}{*&<&'string1'&>&*}{*&<&'string2'&>&*}&&&
9316 {*&<&'string3'&>&*}}*&"
9317 .cindex "expansion" "extracting substrings by key"
9318 .cindex "&%extract%&" "substrings by key"
9319 The key and <&'string1'&> are first expanded separately. Leading and trailing
9320 white space is removed from the key (but not from any of the strings). The key
9321 must not be empty and must not consist entirely of digits.
9322 The expanded <&'string1'&> must be of the form:
9324 <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ...
9327 where the equals signs and spaces (but not both) are optional. If any of the
9328 values contain white space, they must be enclosed in double quotes, and any
9329 values that are enclosed in double quotes are subject to escape processing as
9330 described in section &<<SECTstrings>>&. The expanded <&'string1'&> is searched
9331 for the value that corresponds to the key. The search is case-insensitive. If
9332 the key is found, <&'string2'&> is expanded, and replaces the whole item;
9333 otherwise <&'string3'&> is used. During the expansion of <&'string2'&> the
9334 variable &$value$& contains the value that has been extracted. Afterwards, it
9335 is restored to any previous value it might have had.
9337 If {<&'string3'&>} is omitted, the item is replaced by an empty string if the
9338 key is not found. If {<&'string2'&>} is also omitted, the value that was
9339 extracted is used. Thus, for example, these two expansions are identical, and
9342 ${extract{gid}{uid=1984 gid=2001}}
9343 ${extract{gid}{uid=1984 gid=2001}{$value}}
9345 Instead of {<&'string3'&>} the word &"fail"& (not in curly brackets) can
9346 appear, for example:
9348 ${extract{Z}{A=... B=...}{$value} fail }
9350 This forces an expansion failure (see section &<<SECTforexpfai>>&);
9351 {<&'string2'&>} must be present for &"fail"& to be recognized.
9354 .vitem "&*${extract{*&<&'number'&>&*}{*&<&'separators'&>&*}&&&
9355 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9356 .cindex "expansion" "extracting substrings by number"
9357 .cindex "&%extract%&" "substrings by number"
9358 The <&'number'&> argument must consist entirely of decimal digits,
9359 apart from leading and trailing white space, which is ignored.
9360 This is what distinguishes this form of &%extract%& from the previous kind. It
9361 behaves in the same way, except that, instead of extracting a named field, it
9362 extracts from <&'string1'&> the field whose number is given as the first
9363 argument. You can use &$value$& in <&'string2'&> or &`fail`& instead of
9364 <&'string3'&> as before.
9366 The fields in the string are separated by any one of the characters in the
9367 separator string. These may include space or tab characters.
9368 The first field is numbered one. If the number is negative, the fields are
9369 counted from the end of the string, with the rightmost one numbered -1. If the
9370 number given is zero, the entire string is returned. If the modulus of the
9371 number is greater than the number of fields in the string, the result is the
9372 expansion of <&'string3'&>, or the empty string if <&'string3'&> is not
9373 provided. For example:
9375 ${extract{2}{:}{x:42:99:& Mailer::/bin/bash}}
9379 ${extract{-4}{:}{x:42:99:& Mailer::/bin/bash}}
9381 yields &"99"&. Two successive separators mean that the field between them is
9382 empty (for example, the fifth field above).
9385 .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*&
9386 .cindex "list" "selecting by condition"
9387 .cindex "expansion" "selecting from list by condition"
9389 After expansion, <&'string'&> is interpreted as a list, colon-separated by
9390 default, but the separator can be changed in the usual way. For each item
9391 in this list, its value is place in &$item$&, and then the condition is
9392 evaluated. If the condition is true, &$item$& is added to the output as an
9393 item in a new list; if the condition is false, the item is discarded. The
9394 separator used for the output list is the same as the one used for the
9395 input, but a separator setting is not included in the output. For example:
9397 ${filter{a:b:c}{!eq{$item}{b}}}
9399 yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
9400 to what it was before. See also the &*map*& and &*reduce*& expansion items.
9403 .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9404 .cindex "hash function" "textual"
9405 .cindex "expansion" "textual hash"
9406 This is a textual hashing function, and was the first to be implemented in
9407 early versions of Exim. In current releases, there are other hashing functions
9408 (numeric, MD5, and SHA-1), which are described below.
9410 The first two strings, after expansion, must be numbers. Call them <&'m'&> and
9411 <&'n'&>. If you are using fixed values for these numbers, that is, if
9412 <&'string1'&> and <&'string2'&> do not change when they are expanded, you can
9413 use the simpler operator notation that avoids some of the braces:
9415 ${hash_<n>_<m>:<string>}
9417 The second number is optional (in both notations). If <&'n'&> is greater than
9418 or equal to the length of the string, the expansion item returns the string.
9419 Otherwise it computes a new string of length <&'n'&> by applying a hashing
9420 function to the string. The new string consists of characters taken from the
9421 first <&'m'&> characters of the string
9423 abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQWRSTUVWXYZ0123456789
9425 If <&'m'&> is not present the value 26 is used, so that only lower case
9426 letters appear. For example:
9428 &`$hash{3}{monty}} `& yields &`jmg`&
9429 &`$hash{5}{monty}} `& yields &`monty`&
9430 &`$hash{4}{62}{monty python}}`& yields &`fbWx`&
9433 .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&&
9434 &*$h_*&<&'header&~name'&>&*:*&" &&&
9435 "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9436 &*$bh_*&<&'header&~name'&>&*:*&" &&&
9437 "&*$lheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9438 &*$lh_*&<&'header&~name'&>&*:*&"
9439 "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&&
9440 &*$rh_*&<&'header&~name'&>&*:*&"
9441 .cindex "expansion" "header insertion"
9442 .vindex "&$header_$&"
9443 .vindex "&$bheader_$&"
9444 .vindex "&$lheader_$&"
9445 .vindex "&$rheader_$&"
9446 .cindex "header lines" "in expansion strings"
9447 .cindex "header lines" "character sets"
9448 .cindex "header lines" "decoding"
9449 Substitute the contents of the named message header line, for example
9453 The newline that terminates a header line is not included in the expansion, but
9454 internal newlines (caused by splitting the header line over several physical
9455 lines) may be present.
9457 The difference between the four pairs of expansions is in the way
9458 the data in the header line is interpreted.
9461 .cindex "white space" "in header lines"
9462 &%rheader%& gives the original &"raw"& content of the header line, with no
9463 processing at all, and without the removal of leading and trailing white space.
9466 .cindex "list" "of header lines"
9467 &%lheader%& gives a colon-separated list, one element per header when there
9468 are multiple headers with a given name.
9469 Any embedded colon characters within an element are doubled, so normal Exim
9470 list-processing facilities can be used.
9471 The terminating newline of each element is removed; in other respects
9472 the content is &"raw"&.
9475 .cindex "base64 encoding" "in header lines"
9476 &%bheader%& removes leading and trailing white space, and then decodes base64
9477 or quoted-printable MIME &"words"& within the header text, but does no
9478 character set translation. If decoding of what looks superficially like a MIME
9479 &"word"& fails, the raw string is returned. If decoding
9480 .cindex "binary zero" "in header line"
9481 produces a binary zero character, it is replaced by a question mark &-- this is
9482 what Exim does for binary zeros that are actually received in header lines.
9485 &%header%& tries to translate the string as decoded by &%bheader%& to a
9486 standard character set. This is an attempt to produce the same string as would
9487 be displayed on a user's MUA. If translation fails, the &%bheader%& string is
9488 returned. Translation is attempted only on operating systems that support the
9489 &[iconv()]& function. This is indicated by the compile-time macro HAVE_ICONV in
9490 a system Makefile or in &_Local/Makefile_&.
9493 In a filter file, the target character set for &%header%& can be specified by a
9494 command of the following form:
9496 headers charset "UTF-8"
9498 This command affects all references to &$h_$& (or &$header_$&) expansions in
9499 subsequently obeyed filter commands. In the absence of this command, the target
9500 character set in a filter is taken from the setting of the &%headers_charset%&
9501 option in the runtime configuration. The value of this option defaults to the
9502 value of HEADERS_CHARSET in &_Local/Makefile_&. The ultimate default is
9505 Header names follow the syntax of RFC 2822, which states that they may contain
9506 any printing characters except space and colon. Consequently, curly brackets
9507 &'do not'& terminate header names, and should not be used to enclose them as
9508 if they were variables. Attempting to do so causes a syntax error.
9510 Only header lines that are common to all copies of a message are visible to
9511 this mechanism. These are the original header lines that are received with the
9512 message, and any that are added by an ACL statement or by a system
9513 filter. Header lines that are added to a particular copy of a message by a
9514 router or transport are not accessible.
9516 For incoming SMTP messages, no header lines are visible in
9517 ACLs that are obeyed before the data phase completes,
9518 because the header structure is not set up until the message is received.
9519 They are visible in DKIM, PRDR and DATA ACLs.
9520 Header lines that are added in a RCPT ACL (for example)
9521 are saved until the message's incoming header lines are available, at which
9522 point they are added.
9523 When any of the above ACLs ar
9524 running, however, header lines added by earlier ACLs are visible.
9526 Upper case and lower case letters are synonymous in header names. If the
9527 following character is white space, the terminating colon may be omitted, but
9528 this is not recommended, because you may then forget it when it is needed. When
9529 white space terminates the header name, this white space is included in the
9530 expanded string. If the message does not contain the given header, the
9531 expansion item is replaced by an empty string. (See the &%def%& condition in
9532 section &<<SECTexpcond>>& for a means of testing for the existence of a
9535 If there is more than one header with the same name, they are all concatenated
9536 to form the substitution string, up to a maximum length of 64K. Unless
9537 &%rheader%& is being used, leading and trailing white space is removed from
9538 each header before concatenation, and a completely empty header is ignored. A
9539 newline character is then inserted between non-empty headers, but there is no
9540 newline at the very end. For the &%header%& and &%bheader%& expansion, for
9541 those headers that contain lists of addresses, a comma is also inserted at the
9542 junctions between headers. This does not happen for the &%rheader%& expansion.
9545 .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
9546 .cindex "expansion" "hmac hashing"
9548 This function uses cryptographic hashing (either MD5 or SHA-1) to convert a
9549 shared secret and some text into a message authentication code, as specified in
9550 RFC 2104. This differs from &`${md5:secret_text...}`& or
9551 &`${sha1:secret_text...}`& in that the hmac step adds a signature to the
9552 cryptographic hash, allowing for authentication that is not possible with MD5
9553 or SHA-1 alone. The hash name must expand to either &`md5`& or &`sha1`& at
9554 present. For example:
9556 ${hmac{md5}{somesecret}{$primary_hostname $tod_log}}
9558 For the hostname &'mail.example.com'& and time 2002-10-17 11:30:59, this
9561 dd97e3ba5d1a61b5006108f8c8252953
9563 As an example of how this might be used, you might put in the main part of
9564 an Exim configuration:
9566 SPAMSCAN_SECRET=cohgheeLei2thahw
9568 In a router or a transport you could then have:
9571 X-Spam-Scanned: ${primary_hostname} ${message_exim_id} \
9572 ${hmac{md5}{SPAMSCAN_SECRET}\
9573 {${primary_hostname},${message_exim_id},$h_message-id:}}
9575 Then given a message, you can check where it was scanned by looking at the
9576 &'X-Spam-Scanned:'& header line. If you know the secret, you can check that
9577 this header line is authentic by recomputing the authentication code from the
9578 host name, message ID and the &'Message-id:'& header line. This can be done
9579 using Exim's &%-be%& option, or by other means, for example by using the
9580 &'hmac_md5_hex()'& function in Perl.
9583 .vitem &*${if&~*&<&'condition'&>&*&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9584 .cindex "expansion" "conditional"
9585 .cindex "&%if%&, expansion item"
9586 If <&'condition'&> is true, <&'string1'&> is expanded and replaces the whole
9587 item; otherwise <&'string2'&> is used. The available conditions are described
9588 in section &<<SECTexpcond>>& below. For example:
9590 ${if eq {$local_part}{postmaster} {yes}{no} }
9592 The second string need not be present; if it is not and the condition is not
9593 true, the item is replaced with nothing. Alternatively, the word &"fail"& may
9594 be present instead of the second string (without any curly brackets). In this
9595 case, the expansion is forced to fail if the condition is not true (see section
9596 &<<SECTforexpfai>>&).
9598 If both strings are omitted, the result is the string &`true`& if the condition
9599 is true, and the empty string if the condition is false. This makes it less
9600 cumbersome to write custom ACL and router conditions. For example, instead of
9602 condition = ${if >{$acl_m4}{3}{true}{false}}
9606 condition = ${if >{$acl_m4}{3}}
9611 .vitem &*${imapfolder{*&<&'foldername'&>&*}}*&
9612 .cindex expansion "imap folder"
9613 .cindex "&%imapfolder%& expansion item"
9614 This item converts a (possibly multilevel, or with non-ASCII characters)
9615 folder specification to a Maildir name for filesystem use.
9616 For information on internationalisation support see &<<SECTi18nMDA>>&.
9620 .vitem &*${length{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9621 .cindex "expansion" "string truncation"
9622 .cindex "&%length%& expansion item"
9623 The &%length%& item is used to extract the initial portion of a string. Both
9624 strings are expanded, and the first one must yield a number, <&'n'&>, say. If
9625 you are using a fixed value for the number, that is, if <&'string1'&> does not
9626 change when expanded, you can use the simpler operator notation that avoids
9629 ${length_<n>:<string>}
9631 The result of this item is either the first <&'n'&> characters or the whole
9632 of <&'string2'&>, whichever is the shorter. Do not confuse &%length%& with
9633 &%strlen%&, which gives the length of a string.
9636 .vitem "&*${listextract{*&<&'number'&>&*}&&&
9637 {*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&"
9638 .cindex "expansion" "extracting list elements by number"
9639 .cindex "&%listextract%&" "extract list elements by number"
9640 .cindex "list" "extracting elements by number"
9641 The <&'number'&> argument must consist entirely of decimal digits,
9642 apart from an optional leading minus,
9643 and leading and trailing white space (which is ignored).
9645 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9646 default, but the separator can be changed in the usual way.
9648 The first field of the list is numbered one.
9649 If the number is negative, the fields are
9650 counted from the end of the list, with the rightmost one numbered -1.
9651 The numbered element of the list is extracted and placed in &$value$&,
9652 then <&'string2'&> is expanded as the result.
9654 If the modulus of the
9655 number is zero or greater than the number of fields in the string,
9656 the result is the expansion of <&'string3'&>.
9660 ${listextract{2}{x:42:99}}
9664 ${listextract{-3}{<, x,42,99,& Mailer,,/bin/bash}{result: $value}}
9666 yields &"result: 42"&.
9668 If {<&'string3'&>} is omitted, an empty string is used for string3.
9669 If {<&'string2'&>} is also omitted, the value that was
9671 You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
9674 .vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
9675 {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9676 This is the first of one of two different types of lookup item, which are both
9677 described in the next item.
9679 .vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
9680 {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
9681 .cindex "expansion" "lookup in"
9682 .cindex "file" "lookups"
9683 .cindex "lookup" "in expanded string"
9684 The two forms of lookup item specify data lookups in files and databases, as
9685 discussed in chapter &<<CHAPfdlookup>>&. The first form is used for single-key
9686 lookups, and the second is used for query-style lookups. The <&'key'&>,
9687 <&'file'&>, and <&'query'&> strings are expanded before use.
9689 If there is any white space in a lookup item which is part of a filter command,
9690 a retry or rewrite rule, a routing rule for the &(manualroute)& router, or any
9691 other place where white space is significant, the lookup item must be enclosed
9692 in double quotes. The use of data lookups in users' filter files may be locked
9693 out by the system administrator.
9696 If the lookup succeeds, <&'string1'&> is expanded and replaces the entire item.
9697 During its expansion, the variable &$value$& contains the data returned by the
9698 lookup. Afterwards it reverts to the value it had previously (at the outer
9699 level it is empty). If the lookup fails, <&'string2'&> is expanded and replaces
9700 the entire item. If {<&'string2'&>} is omitted, the replacement is the empty
9701 string on failure. If <&'string2'&> is provided, it can itself be a nested
9702 lookup, thus providing a mechanism for looking up a default value when the
9703 original lookup fails.
9705 If a nested lookup is used as part of <&'string1'&>, &$value$& contains the
9706 data for the outer lookup while the parameters of the second lookup are
9707 expanded, and also while <&'string2'&> of the second lookup is expanded, should
9708 the second lookup fail. Instead of {<&'string2'&>} the word &"fail"& can
9709 appear, and in this case, if the lookup fails, the entire expansion is forced
9710 to fail (see section &<<SECTforexpfai>>&). If both {<&'string1'&>} and
9711 {<&'string2'&>} are omitted, the result is the looked up value in the case of a
9712 successful lookup, and nothing in the case of failure.
9714 For single-key lookups, the string &"partial"& is permitted to precede the
9715 search type in order to do partial matching, and * or *@ may follow a search
9716 type to request default lookups if the key does not match (see sections
9717 &<<SECTdefaultvaluelookups>>& and &<<SECTpartiallookup>>& for details).
9719 .cindex "numerical variables (&$1$& &$2$& etc)" "in lookup expansion"
9720 If a partial search is used, the variables &$1$& and &$2$& contain the wild
9721 and non-wild parts of the key during the expansion of the replacement text.
9722 They return to their previous values at the end of the lookup item.
9724 This example looks up the postmaster alias in the conventional alias file:
9726 ${lookup {postmaster} lsearch {/etc/aliases} {$value}}
9728 This example uses NIS+ to look up the full name of the user corresponding to
9729 the local part of an address, forcing the expansion to fail if it is not found:
9731 ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \
9736 .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*&
9737 .cindex "expansion" "list creation"
9739 After expansion, <&'string1'&> is interpreted as a list, colon-separated by
9740 default, but the separator can be changed in the usual way. For each item
9741 in this list, its value is place in &$item$&, and then <&'string2'&> is
9742 expanded and added to the output as an item in a new list. The separator used
9743 for the output list is the same as the one used for the input, but a separator
9744 setting is not included in the output. For example:
9746 ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
9748 expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
9749 value of &$item$& is restored to what it was before. See also the &*filter*&
9750 and &*reduce*& expansion items.
9752 .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9753 .cindex "expansion" "numeric hash"
9754 .cindex "hash function" "numeric"
9755 The three strings are expanded; the first two must yield numbers. Call them
9756 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
9757 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
9758 can use the simpler operator notation that avoids some of the braces:
9760 ${nhash_<n>_<m>:<string>}
9762 The second number is optional (in both notations). If there is only one number,
9763 the result is a number in the range 0&--<&'n'&>-1. Otherwise, the string is
9764 processed by a div/mod hash function that returns two numbers, separated by a
9765 slash, in the ranges 0 to <&'n'&>-1 and 0 to <&'m'&>-1, respectively. For
9768 ${nhash{8}{64}{supercalifragilisticexpialidocious}}
9770 returns the string &"6/33"&.
9774 .vitem &*${perl{*&<&'subroutine'&>&*}{*&<&'arg'&>&*}{*&<&'arg'&>&*}...}*&
9775 .cindex "Perl" "use in expanded string"
9776 .cindex "expansion" "calling Perl from"
9777 This item is available only if Exim has been built to include an embedded Perl
9778 interpreter. The subroutine name and the arguments are first separately
9779 expanded, and then the Perl subroutine is called with those arguments. No
9780 additional arguments need be given; the maximum number permitted, including the
9781 name of the subroutine, is nine.
9783 The return value of the subroutine is inserted into the expanded string, unless
9784 the return value is &%undef%&. In that case, the expansion fails in the same
9785 way as an explicit &"fail"& on a lookup item. The return value is a scalar.
9786 Whatever you return is evaluated in a scalar context. For example, if you
9787 return the name of a Perl vector, the return value is the size of the vector,
9790 If the subroutine exits by calling Perl's &%die%& function, the expansion fails
9791 with the error message that was passed to &%die%&. More details of the embedded
9792 Perl facility are given in chapter &<<CHAPperl>>&.
9794 The &(redirect)& router has an option called &%forbid_filter_perl%& which locks
9795 out the use of this expansion item in filter files.
9798 .vitem &*${prvs{*&<&'address'&>&*}{*&<&'secret'&>&*}{*&<&'keynumber'&>&*}}*&
9799 .cindex "&%prvs%& expansion item"
9800 The first argument is a complete email address and the second is secret
9801 keystring. The third argument, specifying a key number, is optional. If absent,
9802 it defaults to 0. The result of the expansion is a prvs-signed email address,
9803 to be typically used with the &%return_path%& option on an &(smtp)& transport
9804 as part of a bounce address tag validation (BATV) scheme. For more discussion
9805 and an example, see section &<<SECTverifyPRVS>>&.
9807 .vitem "&*${prvscheck{*&<&'address'&>&*}{*&<&'secret'&>&*}&&&
9808 {*&<&'string'&>&*}}*&"
9809 .cindex "&%prvscheck%& expansion item"
9810 This expansion item is the complement of the &%prvs%& item. It is used for
9811 checking prvs-signed addresses. If the expansion of the first argument does not
9812 yield a syntactically valid prvs-signed address, the whole item expands to the
9813 empty string. When the first argument does expand to a syntactically valid
9814 prvs-signed address, the second argument is expanded, with the prvs-decoded
9815 version of the address and the key number extracted from the address in the
9816 variables &$prvscheck_address$& and &$prvscheck_keynum$&, respectively.
9818 These two variables can be used in the expansion of the second argument to
9819 retrieve the secret. The validity of the prvs-signed address is then checked
9820 against the secret. The result is stored in the variable &$prvscheck_result$&,
9821 which is empty for failure or &"1"& for success.
9823 The third argument is optional; if it is missing, it defaults to an empty
9824 string. This argument is now expanded. If the result is an empty string, the
9825 result of the expansion is the decoded version of the address. This is the case
9826 whether or not the signature was valid. Otherwise, the result of the expansion
9827 is the expansion of the third argument.
9829 All three variables can be used in the expansion of the third argument.
9830 However, once the expansion is complete, only &$prvscheck_result$& remains set.
9831 For more discussion and an example, see section &<<SECTverifyPRVS>>&.
9833 .vitem &*${readfile{*&<&'file&~name'&>&*}{*&<&'eol&~string'&>&*}}*&
9834 .cindex "expansion" "inserting an entire file"
9835 .cindex "file" "inserting into expansion"
9836 .cindex "&%readfile%& expansion item"
9837 The file name and end-of-line string are first expanded separately. The file is
9838 then read, and its contents replace the entire item. All newline characters in
9839 the file are replaced by the end-of-line string if it is present. Otherwise,
9840 newlines are left in the string.
9841 String expansion is not applied to the contents of the file. If you want this,
9842 you must wrap the item in an &%expand%& operator. If the file cannot be read,
9843 the string expansion fails.
9845 The &(redirect)& router has an option called &%forbid_filter_readfile%& which
9846 locks out the use of this expansion item in filter files.
9850 .vitem "&*${readsocket{*&<&'name'&>&*}{*&<&'request'&>&*}&&&
9851 {*&<&'options'&>&*}{*&<&'eol&~string'&>&*}{*&<&'fail&~string'&>&*}}*&"
9852 .cindex "expansion" "inserting from a socket"
9853 .cindex "socket, use of in expansion"
9854 .cindex "&%readsocket%& expansion item"
9855 This item inserts data from a Unix domain or TCP socket into the expanded
9856 string. The minimal way of using it uses just two arguments, as in these
9859 ${readsocket{/socket/name}{request string}}
9860 ${readsocket{inet:some.host:1234}{request string}}
9862 For a Unix domain socket, the first substring must be the path to the socket.
9863 For an Internet socket, the first substring must contain &`inet:`& followed by
9864 a host name or IP address, followed by a colon and a port, which can be a
9865 number or the name of a TCP port in &_/etc/services_&. An IP address may
9866 optionally be enclosed in square brackets. This is best for IPv6 addresses. For
9869 ${readsocket{inet:[::1]:1234}{request string}}
9871 Only a single host name may be given, but if looking it up yields more than
9872 one IP address, they are each tried in turn until a connection is made. For
9873 both kinds of socket, Exim makes a connection, writes the request string
9874 unless it is an empty string; and no terminating NUL is ever sent)
9875 and reads from the socket until an end-of-file
9876 is read. A timeout of 5 seconds is applied. Additional, optional arguments
9877 extend what can be done. Firstly, you can vary the timeout. For example:
9879 ${readsocket{/socket/name}{request string}{3s}}
9882 The third argument is a list of options, of which the first element is the timeout
9883 and must be present if the argument is given.
9884 Further elements are options of form &'name=value'&.
9885 Two option types is currently recognised: shutdown and tls.
9886 The first defines whether (the default)
9887 or not a shutdown is done on the connection after sending the request.
9888 Example, to not do so (preferred, eg. by some webservers):
9890 ${readsocket{/socket/name}{request string}{3s:shutdown=no}}
9893 The second, tls, controls the use of TLS on the connection. Example:
9895 ${readsocket{/socket/name}{request string}{3s:tls=yes}}
9897 The default is to not use TLS.
9898 If it is enabled, a shutdown as descripbed above is never done.
9901 A fourth argument allows you to change any newlines that are in the data
9902 that is read, in the same way as for &%readfile%& (see above). This example
9903 turns them into spaces:
9905 ${readsocket{inet:127.0.0.1:3294}{request string}{3s}{ }}
9907 As with all expansions, the substrings are expanded before the processing
9908 happens. Errors in these sub-expansions cause the expansion to fail. In
9909 addition, the following errors can occur:
9912 Failure to create a socket file descriptor;
9914 Failure to connect the socket;
9916 Failure to write the request string;
9918 Timeout on reading from the socket.
9921 By default, any of these errors causes the expansion to fail. However, if
9922 you supply a fifth substring, it is expanded and used when any of the above
9923 errors occurs. For example:
9925 ${readsocket{/socket/name}{request string}{3s}{\n}\
9928 You can test for the existence of a Unix domain socket by wrapping this
9929 expansion in &`${if exists`&, but there is a race condition between that test
9930 and the actual opening of the socket, so it is safer to use the fifth argument
9931 if you want to be absolutely sure of avoiding an expansion error for a
9932 non-existent Unix domain socket, or a failure to connect to an Internet socket.
9934 The &(redirect)& router has an option called &%forbid_filter_readsocket%& which
9935 locks out the use of this expansion item in filter files.
9938 .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*&
9939 .cindex "expansion" "reducing a list to a scalar"
9940 .cindex "list" "reducing to a scalar"
9943 This operation reduces a list to a single, scalar string. After expansion,
9944 <&'string1'&> is interpreted as a list, colon-separated by default, but the
9945 separator can be changed in the usual way. Then <&'string2'&> is expanded and
9946 assigned to the &$value$& variable. After this, each item in the <&'string1'&>
9947 list is assigned to &$item$& in turn, and <&'string3'&> is expanded for each of
9948 them. The result of that expansion is assigned to &$value$& before the next
9949 iteration. When the end of the list is reached, the final value of &$value$& is
9950 added to the expansion output. The &*reduce*& expansion item can be used in a
9951 number of ways. For example, to add up a list of numbers:
9953 ${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
9955 The result of that expansion would be &`6`&. The maximum of a list of numbers
9958 ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
9960 At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
9961 restored to what they were before. See also the &*filter*& and &*map*&
9964 .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
9965 This item inserts &"raw"& header lines. It is described with the &%header%&
9966 expansion item above.
9968 .vitem "&*${run{*&<&'command'&>&*&~*&<&'args'&>&*}{*&<&'string1'&>&*}&&&
9969 {*&<&'string2'&>&*}}*&"
9970 .cindex "expansion" "running a command"
9971 .cindex "&%run%& expansion item"
9972 The command and its arguments are first expanded as one string. The string is
9973 split apart into individual arguments by spaces, and then the command is run
9974 in a separate process, but under the same uid and gid. As in other command
9975 executions from Exim, a shell is not used by default. If the command requires
9976 a shell, you must explicitly code it.
9978 Since the arguments are split by spaces, when there is a variable expansion
9979 which has an empty result, it will cause the situation that the argument will
9980 simply be omitted when the program is actually executed by Exim. If the
9981 script/program requires a specific number of arguments and the expanded
9982 variable could possibly result in this empty expansion, the variable must be
9983 quoted. This is more difficult if the expanded variable itself could result
9984 in a string containing quotes, because it would interfere with the quotes
9985 around the command arguments. A possible guard against this is to wrap the
9986 variable in the &%sg%& operator to change any quote marks to some other
9989 The standard input for the command exists, but is empty. The standard output
9990 and standard error are set to the same file descriptor.
9991 .cindex "return code" "from &%run%& expansion"
9993 If the command succeeds (gives a zero return code) <&'string1'&> is expanded
9994 and replaces the entire item; during this expansion, the standard output/error
9995 from the command is in the variable &$value$&. If the command fails,
9996 <&'string2'&>, if present, is expanded and used. Once again, during the
9997 expansion, the standard output/error from the command is in the variable
10000 If <&'string2'&> is absent, the result is empty. Alternatively, <&'string2'&>
10001 can be the word &"fail"& (not in braces) to force expansion failure if the
10002 command does not succeed. If both strings are omitted, the result is contents
10003 of the standard output/error on success, and nothing on failure.
10005 .vindex "&$run_in_acl$&"
10006 The standard output/error of the command is put in the variable &$value$&.
10007 In this ACL example, the output of a command is logged for the admin to
10010 warn condition = ${run{/usr/bin/id}{yes}{no}}
10011 log_message = Output of id: $value
10013 If the command requires shell idioms, such as the > redirect operator, the
10014 shell must be invoked directly, such as with:
10016 ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}}
10019 .vindex "&$runrc$&"
10020 The return code from the command is put in the variable &$runrc$&, and this
10021 remains set afterwards, so in a filter file you can do things like this:
10023 if "${run{x y z}{}}$runrc" is 1 then ...
10024 elif $runrc is 2 then ...
10028 If execution of the command fails (for example, the command does not exist),
10029 the return code is 127 &-- the same code that shells use for non-existent
10032 &*Warning*&: In a router or transport, you cannot assume the order in which
10033 option values are expanded, except for those preconditions whose order of
10034 testing is documented. Therefore, you cannot reliably expect to set &$runrc$&
10035 by the expansion of one option, and use it in another.
10037 The &(redirect)& router has an option called &%forbid_filter_run%& which locks
10038 out the use of this expansion item in filter files.
10041 .vitem &*${sg{*&<&'subject'&>&*}{*&<&'regex'&>&*}{*&<&'replacement'&>&*}}*&
10042 .cindex "expansion" "string substitution"
10043 .cindex "&%sg%& expansion item"
10044 This item works like Perl's substitution operator (s) with the global (/g)
10045 option; hence its name. However, unlike the Perl equivalent, Exim does not
10046 modify the subject string; instead it returns the modified string for insertion
10047 into the overall expansion. The item takes three arguments: the subject string,
10048 a regular expression, and a substitution string. For example:
10050 ${sg{abcdefabcdef}{abc}{xyz}}
10052 yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
10053 if any $, } or \ characters are required in the regular expression or in the
10054 substitution string, they have to be escaped. For example:
10056 ${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
10058 yields &"defabc"&, and
10060 ${sg{1=A 4=D 3=C}{\N(\d+)=\N}{K\$1=}}
10062 yields &"K1=A K4=D K3=C"&. Note the use of &`\N`& to protect the contents of
10063 the regular expression from string expansion.
10067 .vitem &*${sort{*&<&'string'&>&*}{*&<&'comparator'&>&*}{*&<&'extractor'&>&*}}*&
10068 .cindex sorting "a list"
10069 .cindex list sorting
10070 .cindex expansion "list sorting"
10071 After expansion, <&'string'&> is interpreted as a list, colon-separated by
10072 default, but the separator can be changed in the usual way.
10073 The <&'comparator'&> argument is interpreted as the operator
10074 of a two-argument expansion condition.
10075 The numeric operators plus ge, gt, le, lt (and ~i variants) are supported.
10076 The comparison should return true when applied to two values
10077 if the first value should sort before the second value.
10078 The <&'extractor'&> expansion is applied repeatedly to elements of the list,
10079 the element being placed in &$item$&,
10080 to give values for comparison.
10082 The item result is a sorted list,
10083 with the original list separator,
10084 of the list elements (in full) of the original.
10088 ${sort{3:2:1:4}{<}{$item}}
10090 sorts a list of numbers, and
10092 ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}}
10094 will sort an MX lookup into priority order.
10097 .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
10098 .cindex "&%substr%& expansion item"
10099 .cindex "substring extraction"
10100 .cindex "expansion" "substring extraction"
10101 The three strings are expanded; the first two must yield numbers. Call them
10102 <&'n'&> and <&'m'&>. If you are using fixed values for these numbers, that is,
10103 if <&'string1'&> and <&'string2'&> do not change when they are expanded, you
10104 can use the simpler operator notation that avoids some of the braces:
10106 ${substr_<n>_<m>:<string>}
10108 The second number is optional (in both notations).
10109 If it is absent in the simpler format, the preceding underscore must also be
10112 The &%substr%& item can be used to extract more general substrings than
10113 &%length%&. The first number, <&'n'&>, is a starting offset, and <&'m'&> is the
10114 length required. For example
10116 ${substr{3}{2}{$local_part}}
10118 If the starting offset is greater than the string length the result is the
10119 null string; if the length plus starting offset is greater than the string
10120 length, the result is the right-hand part of the string, starting from the
10121 given offset. The first character in the string has offset zero.
10123 The &%substr%& expansion item can take negative offset values to count
10124 from the right-hand end of its operand. The last character is offset -1, the
10125 second-last is offset -2, and so on. Thus, for example,
10127 ${substr{-5}{2}{1234567}}
10129 yields &"34"&. If the absolute value of a negative offset is greater than the
10130 length of the string, the substring starts at the beginning of the string, and
10131 the length is reduced by the amount of overshoot. Thus, for example,
10133 ${substr{-5}{2}{12}}
10135 yields an empty string, but
10137 ${substr{-3}{2}{12}}
10141 When the second number is omitted from &%substr%&, the remainder of the string
10142 is taken if the offset is positive. If it is negative, all characters in the
10143 string preceding the offset point are taken. For example, an offset of -1 and
10144 no length, as in these semantically identical examples:
10147 ${substr{-1}{abcde}}
10149 yields all but the last character of the string, that is, &"abcd"&.
10153 .vitem "&*${tr{*&<&'subject'&>&*}{*&<&'characters'&>&*}&&&
10154 {*&<&'replacements'&>&*}}*&"
10155 .cindex "expansion" "character translation"
10156 .cindex "&%tr%& expansion item"
10157 This item does single-character translation on its subject string. The second
10158 argument is a list of characters to be translated in the subject string. Each
10159 matching character is replaced by the corresponding character from the
10160 replacement list. For example
10162 ${tr{abcdea}{ac}{13}}
10164 yields &`1b3de1`&. If there are duplicates in the second character string, the
10165 last occurrence is used. If the third string is shorter than the second, its
10166 last character is replicated. However, if it is empty, no translation takes
10172 .section "Expansion operators" "SECTexpop"
10173 .cindex "expansion" "operators"
10174 For expansion items that perform transformations on a single argument string,
10175 the &"operator"& notation is used because it is simpler and uses fewer braces.
10176 The substring is first expanded before the operation is applied to it. The
10177 following operations can be performed:
10180 .vitem &*${address:*&<&'string'&>&*}*&
10181 .cindex "expansion" "RFC 2822 address handling"
10182 .cindex "&%address%& expansion item"
10183 The string is interpreted as an RFC 2822 address, as it might appear in a
10184 header line, and the effective address is extracted from it. If the string does
10185 not parse successfully, the result is empty.
10188 .vitem &*${addresses:*&<&'string'&>&*}*&
10189 .cindex "expansion" "RFC 2822 address handling"
10190 .cindex "&%addresses%& expansion item"
10191 The string (after expansion) is interpreted as a list of addresses in RFC
10192 2822 format, such as can be found in a &'To:'& or &'Cc:'& header line. The
10193 operative address (&'local-part@domain'&) is extracted from each item, and the
10194 result of the expansion is a colon-separated list, with appropriate
10195 doubling of colons should any happen to be present in the email addresses.
10196 Syntactically invalid RFC2822 address items are omitted from the output.
10198 It is possible to specify a character other than colon for the output
10199 separator by starting the string with > followed by the new separator
10200 character. For example:
10202 ${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
10204 expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
10205 first, so if the expanded string starts with >, it may change the output
10206 separator unintentionally. This can be avoided by setting the output
10207 separator explicitly:
10209 ${addresses:>:$h_from:}
10212 Compare the &*address*& (singular)
10213 expansion item, which extracts the working address from a single RFC2822
10214 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
10217 To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
10218 a strict interpretation of header line formatting. Exim parses the bare,
10219 unquoted portion of an email address and if it finds a comma, treats it as an
10220 email address separator. For the example header line:
10222 From: =?iso-8859-2?Q?Last=2C_First?= <user@example.com>
10224 The first example below demonstrates that Q-encoded email addresses are parsed
10225 properly if it is given the raw header (in this example, &`$rheader_from:`&).
10226 It does not see the comma because it's still encoded as "=2C". The second
10227 example below is passed the contents of &`$header_from:`&, meaning it gets
10228 de-mimed. Exim sees the decoded "," so it treats it as &*two*& email addresses.
10229 The third example shows that the presence of a comma is skipped when it is
10232 # exim -be '${addresses:From: \
10233 =?iso-8859-2?Q?Last=2C_First?= <user@example.com>}'
10235 # exim -be '${addresses:From: Last, First <user@example.com>}'
10236 Last:user@example.com
10237 # exim -be '${addresses:From: "Last, First" <user@example.com>}'
10241 .vitem &*${base32:*&<&'digits'&>&*}*&
10242 .cindex "&%base32%& expansion item"
10243 .cindex "expansion" "conversion to base 32"
10244 The string must consist entirely of decimal digits. The number is converted to
10245 base 32 and output as a (empty, for zero) string of characters.
10246 Only lowercase letters are used.
10248 .vitem &*${base32d:*&<&'base-32&~digits'&>&*}*&
10249 .cindex "&%base32d%& expansion item"
10250 .cindex "expansion" "conversion to base 32"
10251 The string must consist entirely of base-32 digits.
10252 The number is converted to decimal and output as a string.
10254 .vitem &*${base62:*&<&'digits'&>&*}*&
10255 .cindex "&%base62%& expansion item"
10256 .cindex "expansion" "conversion to base 62"
10257 The string must consist entirely of decimal digits. The number is converted to
10258 base 62 and output as a string of six characters, including leading zeros. In
10259 the few operating environments where Exim uses base 36 instead of base 62 for
10260 its message identifiers (because those systems do not have case-sensitive file
10261 names), base 36 is used by this operator, despite its name. &*Note*&: Just to
10262 be absolutely clear: this is &'not'& base64 encoding.
10264 .vitem &*${base62d:*&<&'base-62&~digits'&>&*}*&
10265 .cindex "&%base62d%& expansion item"
10266 .cindex "expansion" "conversion to base 62"
10267 The string must consist entirely of base-62 digits, or, in operating
10268 environments where Exim uses base 36 instead of base 62 for its message
10269 identifiers, base-36 digits. The number is converted to decimal and output as a
10272 .vitem &*${base64:*&<&'string'&>&*}*&
10273 .cindex "expansion" "base64 encoding"
10274 .cindex "base64 encoding" "in string expansion"
10275 .cindex "&%base64%& expansion item"
10276 .cindex certificate "base64 of DER"
10277 This operator converts a string into one that is base64 encoded.
10279 If the string is a single variable of type certificate,
10280 returns the base64 encoding of the DER form of the certificate.
10283 .vitem &*${base64d:*&<&'string'&>&*}*&
10284 .cindex "expansion" "base64 decoding"
10285 .cindex "base64 decoding" "in string expansion"
10286 .cindex "&%base64d%& expansion item"
10287 This operator converts a base64-encoded string into the un-coded form.
10290 .vitem &*${domain:*&<&'string'&>&*}*&
10291 .cindex "domain" "extraction"
10292 .cindex "expansion" "domain extraction"
10293 The string is interpreted as an RFC 2822 address and the domain is extracted
10294 from it. If the string does not parse successfully, the result is empty.
10297 .vitem &*${escape:*&<&'string'&>&*}*&
10298 .cindex "expansion" "escaping non-printing characters"
10299 .cindex "&%escape%& expansion item"
10300 If the string contains any non-printing characters, they are converted to
10301 escape sequences starting with a backslash. Whether characters with the most
10302 significant bit set (so-called &"8-bit characters"&) count as printing or not
10303 is controlled by the &%print_topbitchars%& option.
10305 .vitem &*${escape8bit:*&<&'string'&>&*}*&
10306 .cindex "expansion" "escaping 8-bit characters"
10307 .cindex "&%escape8bit%& expansion item"
10308 If the string contains and characters with the most significant bit set,
10309 they are converted to escape sequences starting with a backslash.
10310 Backslashes and DEL characters are also converted.
10313 .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*&
10314 .cindex "expansion" "expression evaluation"
10315 .cindex "expansion" "arithmetic expression"
10316 .cindex "&%eval%& expansion item"
10317 These items supports simple arithmetic and bitwise logical operations in
10318 expansion strings. The string (after expansion) must be a conventional
10319 arithmetic expression, but it is limited to basic arithmetic operators, bitwise
10320 logical operators, and parentheses. All operations are carried out using
10321 integer arithmetic. The operator priorities are as follows (the same as in the
10322 C programming language):
10324 .irow &'highest:'& "not (~), negate (-)"
10325 .irow "" "multiply (*), divide (/), remainder (%)"
10326 .irow "" "plus (+), minus (-)"
10327 .irow "" "shift-left (<<), shift-right (>>)"
10328 .irow "" "and (&&)"
10330 .irow &'lowest:'& "or (|)"
10332 Binary operators with the same priority are evaluated from left to right. White
10333 space is permitted before or after operators.
10335 For &%eval%&, numbers may be decimal, octal (starting with &"0"&) or
10336 hexadecimal (starting with &"0x"&). For &%eval10%&, all numbers are taken as
10337 decimal, even if they start with a leading zero; hexadecimal numbers are not
10338 permitted. This can be useful when processing numbers extracted from dates or
10339 times, which often do have leading zeros.
10341 A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024
10343 respectively. Negative numbers are supported. The result of the computation is
10344 a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example:
10347 &`${eval:1+1} `& yields 2
10348 &`${eval:1+2*3} `& yields 7
10349 &`${eval:(1+2)*3} `& yields 9
10350 &`${eval:2+42%5} `& yields 4
10351 &`${eval:0xc&5} `& yields 4
10352 &`${eval:0xc|5} `& yields 13
10353 &`${eval:0xc^5} `& yields 9
10354 &`${eval:0xc>>1} `& yields 6
10355 &`${eval:0xc<<1} `& yields 24
10356 &`${eval:~255&0x1234} `& yields 4608
10357 &`${eval:-(~255&0x1234)} `& yields -4608
10360 As a more realistic example, in an ACL you might have
10362 deny message = Too many bad recipients
10365 {>{$rcpt_count}{10}} \
10368 {$recipients_count} \
10369 {${eval:$rcpt_count/2}} \
10373 The condition is true if there have been more than 10 RCPT commands and
10374 fewer than half of them have resulted in a valid recipient.
10377 .vitem &*${expand:*&<&'string'&>&*}*&
10378 .cindex "expansion" "re-expansion of substring"
10379 The &%expand%& operator causes a string to be expanded for a second time. For
10382 ${expand:${lookup{$domain}dbm{/some/file}{$value}}}
10384 first looks up a string in a file while expanding the operand for &%expand%&,
10385 and then re-expands what it has found.
10388 .vitem &*${from_utf8:*&<&'string'&>&*}*&
10390 .cindex "UTF-8" "conversion from"
10391 .cindex "expansion" "UTF-8 conversion"
10392 .cindex "&%from_utf8%& expansion item"
10393 The world is slowly moving towards Unicode, although there are no standards for
10394 email yet. However, other applications (including some databases) are starting
10395 to store data in Unicode, using UTF-8 encoding. This operator converts from a
10396 UTF-8 string to an ISO-8859-1 string. UTF-8 code values greater than 255 are
10397 converted to underscores. The input must be a valid UTF-8 string. If it is not,
10398 the result is an undefined sequence of bytes.
10400 Unicode code points with values less than 256 are compatible with ASCII and
10401 ISO-8859-1 (also known as Latin-1).
10402 For example, character 169 is the copyright symbol in both cases, though the
10403 way it is encoded is different. In UTF-8, more than one byte is needed for
10404 characters with code values greater than 127, whereas ISO-8859-1 is a
10405 single-byte encoding (but thereby limited to 256 characters). This makes
10406 translation from UTF-8 to ISO-8859-1 straightforward.
10409 .vitem &*${hash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10410 .cindex "hash function" "textual"
10411 .cindex "expansion" "textual hash"
10412 The &%hash%& operator is a simpler interface to the hashing function that can
10413 be used when the two parameters are fixed numbers (as opposed to strings that
10414 change when expanded). The effect is the same as
10416 ${hash{<n>}{<m>}{<string>}}
10418 See the description of the general &%hash%& item above for details. The
10419 abbreviation &%h%& can be used when &%hash%& is used as an operator.
10423 .vitem &*${hex2b64:*&<&'hexstring'&>&*}*&
10424 .cindex "base64 encoding" "conversion from hex"
10425 .cindex "expansion" "hex to base64"
10426 .cindex "&%hex2b64%& expansion item"
10427 This operator converts a hex string into one that is base64 encoded. This can
10428 be useful for processing the output of the MD5 and SHA-1 hashing functions.
10432 .vitem &*${hexquote:*&<&'string'&>&*}*&
10433 .cindex "quoting" "hex-encoded unprintable characters"
10434 .cindex "&%hexquote%& expansion item"
10435 This operator converts non-printable characters in a string into a hex
10436 escape form. Byte values between 33 (!) and 126 (~) inclusive are left
10437 as is, and other byte values are converted to &`\xNN`&, for example a
10438 byte value 127 is converted to &`\x7f`&.
10441 .vitem &*${ipv6denorm:*&<&'string'&>&*}*&
10442 .cindex "&%ipv6denorm%& expansion item"
10443 .cindex "IP address" normalisation
10444 This expands an IPv6 address to a full eight-element colon-separated set
10445 of hex digits including leading zeroes.
10446 A trailing ipv4-style dotted-decimal set is converted to hex.
10447 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10449 .vitem &*${ipv6norm:*&<&'string'&>&*}*&
10450 .cindex "&%ipv6norm%& expansion item"
10451 .cindex "IP address" normalisation
10452 .cindex "IP address" "canonical form"
10453 This converts an IPv6 address to canonical form.
10454 Leading zeroes of groups are omitted, and the longest
10455 set of zero-valued groups is replaced with a double colon.
10456 A trailing ipv4-style dotted-decimal set is converted to hex.
10457 Pure IPv4 addresses are converted to IPv4-mapped IPv6.
10460 .vitem &*${lc:*&<&'string'&>&*}*&
10461 .cindex "case forcing in strings"
10462 .cindex "string" "case forcing"
10463 .cindex "lower casing"
10464 .cindex "expansion" "case forcing"
10465 .cindex "&%lc%& expansion item"
10466 This forces the letters in the string into lower-case, for example:
10471 .vitem &*${length_*&<&'number'&>&*:*&<&'string'&>&*}*&
10472 .cindex "expansion" "string truncation"
10473 .cindex "&%length%& expansion item"
10474 The &%length%& operator is a simpler interface to the &%length%& function that
10475 can be used when the parameter is a fixed number (as opposed to a string that
10476 changes when expanded). The effect is the same as
10478 ${length{<number>}{<string>}}
10480 See the description of the general &%length%& item above for details. Note that
10481 &%length%& is not the same as &%strlen%&. The abbreviation &%l%& can be used
10482 when &%length%& is used as an operator.
10485 .vitem &*${listcount:*&<&'string'&>&*}*&
10486 .cindex "expansion" "list item count"
10487 .cindex "list" "item count"
10488 .cindex "list" "count of items"
10489 .cindex "&%listcount%& expansion item"
10490 The string is interpreted as a list and the number of items is returned.
10493 .vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${listnamed_*&<&'type'&>&*:*&<&'name'&>&*}*&
10494 .cindex "expansion" "named list"
10495 .cindex "&%listnamed%& expansion item"
10496 The name is interpreted as a named list and the content of the list is returned,
10497 expanding any referenced lists, re-quoting as needed for colon-separation.
10498 If the optional type is given it must be one of "a", "d", "h" or "l"
10499 and selects address-, domain-, host- or localpart- lists to search among respectively.
10500 Otherwise all types are searched in an undefined order and the first
10501 matching list is returned.
10504 .vitem &*${local_part:*&<&'string'&>&*}*&
10505 .cindex "expansion" "local part extraction"
10506 .cindex "&%local_part%& expansion item"
10507 The string is interpreted as an RFC 2822 address and the local part is
10508 extracted from it. If the string does not parse successfully, the result is
10512 .vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
10513 .cindex "masked IP address"
10514 .cindex "IP address" "masking"
10515 .cindex "CIDR notation"
10516 .cindex "expansion" "IP address masking"
10517 .cindex "&%mask%& expansion item"
10518 If the form of the string to be operated on is not an IP address followed by a
10519 slash and an integer (that is, a network address in CIDR notation), the
10520 expansion fails. Otherwise, this operator converts the IP address to binary,
10521 masks off the least significant bits according to the bit count, and converts
10522 the result back to text, with mask appended. For example,
10524 ${mask:10.111.131.206/28}
10526 returns the string &"10.111.131.192/28"&. Since this operation is expected to
10527 be mostly used for looking up masked addresses in files, the result for an IPv6
10528 address uses dots to separate components instead of colons, because colon
10529 terminates a key string in lsearch files. So, for example,
10531 ${mask:3ffe:ffff:836f:0a00:000a:0800:200a:c031/99}
10535 3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
10537 Letters in IPv6 addresses are always output in lower case.
10540 .vitem &*${md5:*&<&'string'&>&*}*&
10542 .cindex "expansion" "MD5 hash"
10543 .cindex certificate fingerprint
10544 .cindex "&%md5%& expansion item"
10545 The &%md5%& operator computes the MD5 hash value of the string, and returns it
10546 as a 32-digit hexadecimal number, in which any letters are in lower case.
10548 If the string is a single variable of type certificate,
10549 returns the MD5 hash fingerprint of the certificate.
10552 .vitem &*${nhash_*&<&'n'&>&*_*&<&'m'&>&*:*&<&'string'&>&*}*&
10553 .cindex "expansion" "numeric hash"
10554 .cindex "hash function" "numeric"
10555 The &%nhash%& operator is a simpler interface to the numeric hashing function
10556 that can be used when the two parameters are fixed numbers (as opposed to
10557 strings that change when expanded). The effect is the same as
10559 ${nhash{<n>}{<m>}{<string>}}
10561 See the description of the general &%nhash%& item above for details.
10564 .vitem &*${quote:*&<&'string'&>&*}*&
10565 .cindex "quoting" "in string expansions"
10566 .cindex "expansion" "quoting"
10567 .cindex "&%quote%& expansion item"
10568 The &%quote%& operator puts its argument into double quotes if it
10569 is an empty string or
10570 contains anything other than letters, digits, underscores, dots, and hyphens.
10571 Any occurrences of double quotes and backslashes are escaped with a backslash.
10572 Newlines and carriage returns are converted to &`\n`& and &`\r`&,
10573 respectively For example,
10581 The place where this is useful is when the argument is a substitution from a
10582 variable or a message header.
10584 .vitem &*${quote_local_part:*&<&'string'&>&*}*&
10585 .cindex "&%quote_local_part%& expansion item"
10586 This operator is like &%quote%&, except that it quotes the string only if
10587 required to do so by the rules of RFC 2822 for quoting local parts. For
10588 example, a plus sign would not cause quoting (but it would for &%quote%&).
10589 If you are creating a new email address from the contents of &$local_part$&
10590 (or any other unknown data), you should always use this operator.
10593 .vitem &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*&
10594 .cindex "quoting" "lookup-specific"
10595 This operator applies lookup-specific quoting rules to the string. Each
10596 query-style lookup type has its own quoting rules which are described with
10597 the lookups in chapter &<<CHAPfdlookup>>&. For example,
10599 ${quote_ldap:two * two}
10605 For single-key lookup types, no quoting is ever necessary and this operator
10606 yields an unchanged string.
10609 .vitem &*${randint:*&<&'n'&>&*}*&
10610 .cindex "random number"
10611 This operator returns a somewhat random number which is less than the
10612 supplied number and is at least 0. The quality of this randomness depends
10613 on how Exim was built; the values are not suitable for keying material.
10614 If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used.
10615 If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used,
10616 for versions of GnuTLS with that function.
10617 Otherwise, the implementation may be arc4random(), random() seeded by
10618 srandomdev() or srandom(), or a custom implementation even weaker than
10622 .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*&
10623 .cindex "expansion" "IP address"
10624 This operator reverses an IP address; for IPv4 addresses, the result is in
10625 dotted-quad decimal form, while for IPv6 addresses the result is in
10626 dotted-nibble hexadecimal form. In both cases, this is the "natural" form
10627 for DNS. For example,
10629 ${reverse_ip:192.0.2.4}
10630 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.127}
10635 f.7.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2
10639 .vitem &*${rfc2047:*&<&'string'&>&*}*&
10640 .cindex "expansion" "RFC 2047"
10641 .cindex "RFC 2047" "expansion operator"
10642 .cindex "&%rfc2047%& expansion item"
10643 This operator encodes text according to the rules of RFC 2047. This is an
10644 encoding that is used in header lines to encode non-ASCII characters. It is
10645 assumed that the input string is in the encoding specified by the
10646 &%headers_charset%& option, which gets its default at build time. If the string
10647 contains only characters in the range 33&--126, and no instances of the
10650 ? = ( ) < > @ , ; : \ " . [ ] _
10652 it is not modified. Otherwise, the result is the RFC 2047 encoding of the
10653 string, using as many &"encoded words"& as necessary to encode all the
10657 .vitem &*${rfc2047d:*&<&'string'&>&*}*&
10658 .cindex "expansion" "RFC 2047"
10659 .cindex "RFC 2047" "decoding"
10660 .cindex "&%rfc2047d%& expansion item"
10661 This operator decodes strings that are encoded as per RFC 2047. Binary zero
10662 bytes are replaced by question marks. Characters are converted into the
10663 character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are
10664 not recognized unless &%check_rfc2047_length%& is set false.
10666 &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to
10667 access a header line, RFC 2047 decoding is done automatically. You do not need
10668 to use this operator as well.
10672 .vitem &*${rxquote:*&<&'string'&>&*}*&
10673 .cindex "quoting" "in regular expressions"
10674 .cindex "regular expressions" "quoting"
10675 .cindex "&%rxquote%& expansion item"
10676 The &%rxquote%& operator inserts a backslash before any non-alphanumeric
10677 characters in its argument. This is useful when substituting the values of
10678 variables or headers inside regular expressions.
10681 .vitem &*${sha1:*&<&'string'&>&*}*&
10682 .cindex "SHA-1 hash"
10683 .cindex "expansion" "SHA-1 hashing"
10684 .cindex certificate fingerprint
10685 .cindex "&%sha1%& expansion item"
10686 The &%sha1%& operator computes the SHA-1 hash value of the string, and returns
10687 it as a 40-digit hexadecimal number, in which any letters are in upper case.
10689 If the string is a single variable of type certificate,
10690 returns the SHA-1 hash fingerprint of the certificate.
10693 .vitem &*${sha256:*&<&'string'&>&*}*&
10694 .cindex "SHA-256 hash"
10695 .cindex certificate fingerprint
10696 .cindex "expansion" "SHA-256 hashing"
10697 .cindex "&%sha256%& expansion item"
10698 The &%sha256%& operator computes the SHA-256 hash value of the string
10700 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10702 If the string is a single variable of type certificate,
10703 returns the SHA-256 hash fingerprint of the certificate.
10706 .vitem &*${sha3:*&<&'string'&>&*}*& &&&
10707 &*${sha3_<n>:*&<&'string'&>&*}*&
10708 .cindex "SHA3 hash"
10709 .cindex "expansion" "SHA3 hashing"
10710 .cindex "&%sha3%& expansion item"
10711 The &%sha3%& operator computes the SHA3-256 hash value of the string
10713 it as a 64-digit hexadecimal number, in which any letters are in upper case.
10715 If a number is appended, separated by an underbar, it specifies
10716 the output length. Values of 224, 256, 384 and 512 are accepted;
10717 with 256 being the default.
10719 The &%sha3%& expansion item is only supported if Exim has been
10720 compiled with GnuTLS 3.5.0 or later,
10721 or OpenSSL 1.1.1 or later.
10722 The macro "_CRYPTO_HASH_SHA3" will be defined if it is supported.
10725 .vitem &*${stat:*&<&'string'&>&*}*&
10726 .cindex "expansion" "statting a file"
10727 .cindex "file" "extracting characteristics"
10728 .cindex "&%stat%& expansion item"
10729 The string, after expansion, must be a file path. A call to the &[stat()]&
10730 function is made for this path. If &[stat()]& fails, an error occurs and the
10731 expansion fails. If it succeeds, the data from the stat replaces the item, as a
10732 series of <&'name'&>=<&'value'&> pairs, where the values are all numerical,
10733 except for the value of &"smode"&. The names are: &"mode"& (giving the mode as
10734 a 4-digit octal number), &"smode"& (giving the mode in symbolic format as a
10735 10-character string, as for the &'ls'& command), &"inode"&, &"device"&,
10736 &"links"&, &"uid"&, &"gid"&, &"size"&, &"atime"&, &"mtime"&, and &"ctime"&. You
10737 can extract individual fields using the &%extract%& expansion item.
10739 The use of the &%stat%& expansion in users' filter files can be locked out by
10740 the system administrator. &*Warning*&: The file size may be incorrect on 32-bit
10741 systems for files larger than 2GB.
10743 .vitem &*${str2b64:*&<&'string'&>&*}*&
10744 .cindex "&%str2b64%& expansion item"
10745 Now deprecated, a synonym for the &%base64%& expansion operator.
10749 .vitem &*${strlen:*&<&'string'&>&*}*&
10750 .cindex "expansion" "string length"
10751 .cindex "string" "length in expansion"
10752 .cindex "&%strlen%& expansion item"
10753 The item is replace by the length of the expanded string, expressed as a
10754 decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
10757 .vitem &*${substr_*&<&'start'&>&*_*&<&'length'&>&*:*&<&'string'&>&*}*&
10758 .cindex "&%substr%& expansion item"
10759 .cindex "substring extraction"
10760 .cindex "expansion" "substring expansion"
10761 The &%substr%& operator is a simpler interface to the &%substr%& function that
10762 can be used when the two parameters are fixed numbers (as opposed to strings
10763 that change when expanded). The effect is the same as
10765 ${substr{<start>}{<length>}{<string>}}
10767 See the description of the general &%substr%& item above for details. The
10768 abbreviation &%s%& can be used when &%substr%& is used as an operator.
10770 .vitem &*${time_eval:*&<&'string'&>&*}*&
10771 .cindex "&%time_eval%& expansion item"
10772 .cindex "time interval" "decoding"
10773 This item converts an Exim time interval such as &`2d4h5m`& into a number of
10776 .vitem &*${time_interval:*&<&'string'&>&*}*&
10777 .cindex "&%time_interval%& expansion item"
10778 .cindex "time interval" "formatting"
10779 The argument (after sub-expansion) must be a sequence of decimal digits that
10780 represents an interval of time as a number of seconds. It is converted into a
10781 number of larger units and output in Exim's normal time format, for example,
10784 .vitem &*${uc:*&<&'string'&>&*}*&
10785 .cindex "case forcing in strings"
10786 .cindex "string" "case forcing"
10787 .cindex "upper casing"
10788 .cindex "expansion" "case forcing"
10789 .cindex "&%uc%& expansion item"
10790 This forces the letters in the string into upper-case.
10792 .vitem &*${utf8clean:*&<&'string'&>&*}*&
10793 .cindex "correction of invalid utf-8 sequences in strings"
10794 .cindex "utf-8" "utf-8 sequences"
10795 .cindex "incorrect utf-8"
10796 .cindex "expansion" "utf-8 forcing"
10797 .cindex "&%utf8clean%& expansion item"
10798 This replaces any invalid utf-8 sequence in the string by the character &`?`&.
10800 .vitem "&*${utf8_domain_to_alabel:*&<&'string'&>&*}*&" &&&
10801 "&*${utf8_domain_from_alabel:*&<&'string'&>&*}*&" &&&
10802 "&*${utf8_localpart_to_alabel:*&<&'string'&>&*}*&" &&&
10803 "&*${utf8_localpart_from_alabel:*&<&'string'&>&*}*&"
10804 .cindex expansion UTF-8
10805 .cindex UTF-8 expansion
10807 .cindex internationalisation
10808 .cindex "&%utf8_domain_to_alabel%& expansion item"
10809 .cindex "&%utf8_domain_from_alabel%& expansion item"
10810 .cindex "&%utf8_localpart_to_alabel%& expansion item"
10811 .cindex "&%utf8_localpart_from_alabel%& expansion item"
10812 These convert EAI mail name components between UTF-8 and a-label forms.
10813 For information on internationalisation support see &<<SECTi18nMTA>>&.
10821 .section "Expansion conditions" "SECTexpcond"
10822 .scindex IIDexpcond "expansion" "conditions"
10823 The following conditions are available for testing by the &%${if%& construct
10824 while expanding strings:
10827 .vitem &*!*&<&'condition'&>
10828 .cindex "expansion" "negating a condition"
10829 .cindex "negation" "in expansion condition"
10830 Preceding any condition with an exclamation mark negates the result of the
10833 .vitem <&'symbolic&~operator'&>&~&*{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10834 .cindex "numeric comparison"
10835 .cindex "expansion" "numeric comparison"
10836 There are a number of symbolic operators for doing numeric comparisons. They
10842 &`>= `& greater or equal
10844 &`<= `& less or equal
10848 ${if >{$message_size}{10M} ...
10850 Note that the general negation operator provides for inequality testing. The
10851 two strings must take the form of optionally signed decimal integers,
10852 optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or
10853 lower case), signifying multiplication by 1024, 1024*1024 or 1024*1024*1024, respectively.
10854 As a special case, the numerical value of an empty string is taken as
10857 In all cases, a relative comparator OP is testing if <&'string1'&> OP
10858 <&'string2'&>; the above example is checking if &$message_size$& is larger than
10859 10M, not if 10M is larger than &$message_size$&.
10862 .vitem &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&&
10863 {*&<&'arg2'&>&*}...}*&
10864 .cindex "expansion" "calling an acl"
10865 .cindex "&%acl%&" "expansion condition"
10866 The name and zero to nine argument strings are first expanded separately. The expanded
10867 arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order.
10868 Any unused are made empty. The variable &$acl_narg$& is set to the number of
10869 arguments. The named ACL (see chapter &<<CHAPACL>>&) is called
10870 and may use the variables; if another acl expansion is used the values
10871 are restored after it returns. If the ACL sets
10872 a value using a "message =" modifier the variable $value becomes
10873 the result of the expansion, otherwise it is empty.
10874 If the ACL returns accept the condition is true; if deny, false.
10875 If the ACL returns defer the result is a forced-fail.
10877 .vitem &*bool&~{*&<&'string'&>&*}*&
10878 .cindex "expansion" "boolean parsing"
10879 .cindex "&%bool%& expansion condition"
10880 This condition turns a string holding a true or false representation into
10881 a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"&
10882 (case-insensitively); also integer numbers map to true if non-zero,
10884 An empty string is treated as false.
10885 Leading and trailing whitespace is ignored;
10886 thus a string consisting only of whitespace is false.
10887 All other string values will result in expansion failure.
10889 When combined with ACL variables, this expansion condition will let you
10890 make decisions in one place and act on those decisions in another place.
10893 ${if bool{$acl_m_privileged_sender} ...
10897 .vitem &*bool_lax&~{*&<&'string'&>&*}*&
10898 .cindex "expansion" "boolean parsing"
10899 .cindex "&%bool_lax%& expansion condition"
10900 Like &%bool%&, this condition turns a string into a boolean state. But
10901 where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same
10902 loose definition that the Router &%condition%& option uses. The empty string
10903 and the values &"false"&, &"no"& and &"0"& map to false, all others map to
10904 true. Leading and trailing whitespace is ignored.
10906 Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true.
10908 .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
10909 .cindex "expansion" "encrypted comparison"
10910 .cindex "encrypted strings, comparing"
10911 .cindex "&%crypteq%& expansion condition"
10912 This condition is included in the Exim binary if it is built to support any
10913 authentication mechanisms (see chapter &<<CHAPSMTPAUTH>>&). Otherwise, it is
10914 necessary to define SUPPORT_CRYPTEQ in &_Local/Makefile_& to get &%crypteq%&
10915 included in the binary.
10917 The &%crypteq%& condition has two arguments. The first is encrypted and
10918 compared against the second, which is already encrypted. The second string may
10919 be in the LDAP form for storing encrypted strings, which starts with the
10920 encryption type in curly brackets, followed by the data. If the second string
10921 does not begin with &"{"& it is assumed to be encrypted with &[crypt()]& or
10922 &[crypt16()]& (see below), since such strings cannot begin with &"{"&.
10923 Typically this will be a field from a password file. An example of an encrypted
10924 string in LDAP form is:
10926 {md5}CY9rzUYh03PK3k6DJie09g==
10928 If such a string appears directly in an expansion, the curly brackets have to
10929 be quoted, because they are part of the expansion syntax. For example:
10931 ${if crypteq {test}{\{md5\}CY9rzUYh03PK3k6DJie09g==}{yes}{no}}
10933 The following encryption types (whose names are matched case-independently) are
10938 .cindex "base64 encoding" "in encrypted password"
10939 &%{md5}%& computes the MD5 digest of the first string, and expresses this as
10940 printable characters to compare with the remainder of the second string. If the
10941 length of the comparison string is 24, Exim assumes that it is base64 encoded
10942 (as in the above example). If the length is 32, Exim assumes that it is a
10943 hexadecimal encoding of the MD5 digest. If the length not 24 or 32, the
10947 .cindex "SHA-1 hash"
10948 &%{sha1}%& computes the SHA-1 digest of the first string, and expresses this as
10949 printable characters to compare with the remainder of the second string. If the
10950 length of the comparison string is 28, Exim assumes that it is base64 encoded.
10951 If the length is 40, Exim assumes that it is a hexadecimal encoding of the
10952 SHA-1 digest. If the length is not 28 or 40, the comparison fails.
10955 .cindex "&[crypt()]&"
10956 &%{crypt}%& calls the &[crypt()]& function, which traditionally used to use
10957 only the first eight characters of the password. However, in modern operating
10958 systems this is no longer true, and in many cases the entire password is used,
10959 whatever its length.
10962 .cindex "&[crypt16()]&"
10963 &%{crypt16}%& calls the &[crypt16()]& function, which was originally created to
10964 use up to 16 characters of the password in some operating systems. Again, in
10965 modern operating systems, more characters may be used.
10967 Exim has its own version of &[crypt16()]&, which is just a double call to
10968 &[crypt()]&. For operating systems that have their own version, setting
10969 HAVE_CRYPT16 in &_Local/Makefile_& when building Exim causes it to use the
10970 operating system version instead of its own. This option is set by default in
10971 the OS-dependent &_Makefile_& for those operating systems that are known to
10972 support &[crypt16()]&.
10974 Some years after Exim's &[crypt16()]& was implemented, a user discovered that
10975 it was not using the same algorithm as some operating systems' versions. It
10976 turns out that as well as &[crypt16()]& there is a function called
10977 &[bigcrypt()]& in some operating systems. This may or may not use the same
10978 algorithm, and both of them may be different to Exim's built-in &[crypt16()]&.
10980 However, since there is now a move away from the traditional &[crypt()]&
10981 functions towards using SHA1 and other algorithms, tidying up this area of
10982 Exim is seen as very low priority.
10984 If you do not put a encryption type (in curly brackets) in a &%crypteq%&
10985 comparison, the default is usually either &`{crypt}`& or &`{crypt16}`&, as
10986 determined by the setting of DEFAULT_CRYPT in &_Local/Makefile_&. The default
10987 default is &`{crypt}`&. Whatever the default, you can always use either
10988 function by specifying it explicitly in curly brackets.
10990 .vitem &*def:*&<&'variable&~name'&>
10991 .cindex "expansion" "checking for empty variable"
10992 .cindex "&%def%& expansion condition"
10993 The &%def%& condition must be followed by the name of one of the expansion
10994 variables defined in section &<<SECTexpvar>>&. The condition is true if the
10995 variable does not contain the empty string. For example:
10997 ${if def:sender_ident {from $sender_ident}}
10999 Note that the variable name is given without a leading &%$%& character. If the
11000 variable does not exist, the expansion fails.
11002 .vitem "&*def:header_*&<&'header&~name'&>&*:*&&~&~or&~&&&
11003 &~&*def:h_*&<&'header&~name'&>&*:*&"
11004 .cindex "expansion" "checking header line existence"
11005 This condition is true if a message is being processed and the named header
11006 exists in the message. For example,
11008 ${if def:header_reply-to:{$h_reply-to:}{$h_from:}}
11010 &*Note*&: No &%$%& appears before &%header_%& or &%h_%& in the condition, and
11011 the header name must be terminated by a colon if white space does not follow.
11013 .vitem &*eq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11014 &*eqi&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11015 .cindex "string" "comparison"
11016 .cindex "expansion" "string comparison"
11017 .cindex "&%eq%& expansion condition"
11018 .cindex "&%eqi%& expansion condition"
11019 The two substrings are first expanded. The condition is true if the two
11020 resulting strings are identical. For &%eq%& the comparison includes the case of
11021 letters, whereas for &%eqi%& the comparison is case-independent.
11023 .vitem &*exists&~{*&<&'file&~name'&>&*}*&
11024 .cindex "expansion" "file existence test"
11025 .cindex "file" "existence test"
11026 .cindex "&%exists%&, expansion condition"
11027 The substring is first expanded and then interpreted as an absolute path. The
11028 condition is true if the named file (or directory) exists. The existence test
11029 is done by calling the &[stat()]& function. The use of the &%exists%& test in
11030 users' filter files may be locked out by the system administrator.
11032 .vitem &*first_delivery*&
11033 .cindex "delivery" "first"
11034 .cindex "first delivery"
11035 .cindex "expansion" "first delivery test"
11036 .cindex "&%first_delivery%& expansion condition"
11037 This condition, which has no data, is true during a message's first delivery
11038 attempt. It is false during any subsequent delivery attempts.
11041 .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&&
11042 "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&"
11043 .cindex "list" "iterative conditions"
11044 .cindex "expansion" "&*forall*& condition"
11045 .cindex "expansion" "&*forany*& condition"
11047 These conditions iterate over a list. The first argument is expanded to form
11048 the list. By default, the list separator is a colon, but it can be changed by
11049 the normal method. The second argument is interpreted as a condition that is to
11050 be applied to each item in the list in turn. During the interpretation of the
11051 condition, the current list item is placed in a variable called &$item$&.
11053 For &*forany*&, interpretation stops if the condition is true for any item, and
11054 the result of the whole condition is true. If the condition is false for all
11055 items in the list, the overall condition is false.
11057 For &*forall*&, interpretation stops if the condition is false for any item,
11058 and the result of the whole condition is false. If the condition is true for
11059 all items in the list, the overall condition is true.
11061 Note that negation of &*forany*& means that the condition must be false for all
11062 items for the overall condition to succeed, and negation of &*forall*& means
11063 that the condition must be false for at least one item. In this example, the
11064 list separator is changed to a comma:
11066 ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
11068 The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
11069 being processed, to enable these expansion items to be nested.
11071 To scan a named list, expand it with the &*listnamed*& operator.
11074 .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11075 &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11076 .cindex "string" "comparison"
11077 .cindex "expansion" "string comparison"
11078 .cindex "&%ge%& expansion condition"
11079 .cindex "&%gei%& expansion condition"
11080 The two substrings are first expanded. The condition is true if the first
11081 string is lexically greater than or equal to the second string. For &%ge%& the
11082 comparison includes the case of letters, whereas for &%gei%& the comparison is
11085 .vitem &*gt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11086 &*gti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11087 .cindex "string" "comparison"
11088 .cindex "expansion" "string comparison"
11089 .cindex "&%gt%& expansion condition"
11090 .cindex "&%gti%& expansion condition"
11091 The two substrings are first expanded. The condition is true if the first
11092 string is lexically greater than the second string. For &%gt%& the comparison
11093 includes the case of letters, whereas for &%gti%& the comparison is
11096 .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11097 &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11098 .cindex "string" "comparison"
11099 .cindex "list" "iterative conditions"
11100 Both strings are expanded; the second string is treated as a list of simple
11101 strings; if the first string is a member of the second, then the condition
11104 These are simpler to use versions of the more powerful &*forany*& condition.
11105 Examples, and the &*forany*& equivalents:
11107 ${if inlist{needle}{foo:needle:bar}}
11108 ${if forany{foo:needle:bar}{eq{$item}{needle}}}
11109 ${if inlisti{Needle}{fOo:NeeDLE:bAr}}
11110 ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}}
11113 .vitem &*isip&~{*&<&'string'&>&*}*& &&&
11114 &*isip4&~{*&<&'string'&>&*}*& &&&
11115 &*isip6&~{*&<&'string'&>&*}*&
11116 .cindex "IP address" "testing string format"
11117 .cindex "string" "testing for IP address"
11118 .cindex "&%isip%& expansion condition"
11119 .cindex "&%isip4%& expansion condition"
11120 .cindex "&%isip6%& expansion condition"
11121 The substring is first expanded, and then tested to see if it has the form of
11122 an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas
11123 &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses.
11125 For an IPv4 address, the test is for four dot-separated components, each of
11126 which consists of from one to three digits. For an IPv6 address, up to eight
11127 colon-separated components are permitted, each containing from one to four
11128 hexadecimal digits. There may be fewer than eight components if an empty
11129 component (adjacent colons) is present. Only one empty component is permitted.
11131 &*Note*&: The checks used to be just on the form of the address; actual numerical
11132 values were not considered. Thus, for example, 999.999.999.999 passed the IPv4
11134 This is no longer the case.
11136 The main use of these tests is to distinguish between IP addresses and
11137 host names, or between IPv4 and IPv6 addresses. For example, you could use
11139 ${if isip4{$sender_host_address}...
11141 to test which IP version an incoming SMTP connection is using.
11143 .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*&
11144 .cindex "LDAP" "use for authentication"
11145 .cindex "expansion" "LDAP authentication test"
11146 .cindex "&%ldapauth%& expansion condition"
11147 This condition supports user authentication using LDAP. See section
11148 &<<SECTldap>>& for details of how to use LDAP in lookups and the syntax of
11149 queries. For this use, the query must contain a user name and password. The
11150 query itself is not used, and can be empty. The condition is true if the
11151 password is not empty, and the user name and password are accepted by the LDAP
11152 server. An empty password is rejected without calling LDAP because LDAP binds
11153 with an empty password are considered anonymous regardless of the username, and
11154 will succeed in most configurations. See chapter &<<CHAPSMTPAUTH>>& for details
11155 of SMTP authentication, and chapter &<<CHAPplaintext>>& for an example of how
11159 .vitem &*le&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11160 &*lei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11161 .cindex "string" "comparison"
11162 .cindex "expansion" "string comparison"
11163 .cindex "&%le%& expansion condition"
11164 .cindex "&%lei%& expansion condition"
11165 The two substrings are first expanded. The condition is true if the first
11166 string is lexically less than or equal to the second string. For &%le%& the
11167 comparison includes the case of letters, whereas for &%lei%& the comparison is
11170 .vitem &*lt&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
11171 &*lti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11172 .cindex "string" "comparison"
11173 .cindex "expansion" "string comparison"
11174 .cindex "&%lt%& expansion condition"
11175 .cindex "&%lti%& expansion condition"
11176 The two substrings are first expanded. The condition is true if the first
11177 string is lexically less than the second string. For &%lt%& the comparison
11178 includes the case of letters, whereas for &%lti%& the comparison is
11182 .vitem &*match&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11183 .cindex "expansion" "regular expression comparison"
11184 .cindex "regular expressions" "match in expanded string"
11185 .cindex "&%match%& expansion condition"
11186 The two substrings are first expanded. The second is then treated as a regular
11187 expression and applied to the first. Because of the pre-expansion, if the
11188 regular expression contains dollar, or backslash characters, they must be
11189 escaped. Care must also be taken if the regular expression contains braces
11190 (curly brackets). A closing brace must be escaped so that it is not taken as a
11191 premature termination of <&'string2'&>. The easiest approach is to use the
11192 &`\N`& feature to disable expansion of the regular expression.
11195 ${if match {$local_part}{\N^\d{3}\N} ...
11197 If the whole expansion string is in double quotes, further escaping of
11198 backslashes is also required.
11200 The condition is true if the regular expression match succeeds.
11201 The regular expression is not required to begin with a circumflex
11202 metacharacter, but if there is no circumflex, the expression is not anchored,
11203 and it may match anywhere in the subject, not just at the start. If you want
11204 the pattern to match at the end of the subject, you must include the &`$`&
11205 metacharacter at an appropriate point.
11207 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%if%& expansion"
11208 At the start of an &%if%& expansion the values of the numeric variable
11209 substitutions &$1$& etc. are remembered. Obeying a &%match%& condition that
11210 succeeds causes them to be reset to the substrings of that condition and they
11211 will have these values during the expansion of the success string. At the end
11212 of the &%if%& expansion, the previous values are restored. After testing a
11213 combination of conditions using &%or%&, the subsequent values of the numeric
11214 variables are those of the condition that succeeded.
11216 .vitem &*match_address&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11217 .cindex "&%match_address%& expansion condition"
11218 See &*match_local_part*&.
11220 .vitem &*match_domain&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11221 .cindex "&%match_domain%& expansion condition"
11222 See &*match_local_part*&.
11224 .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11225 .cindex "&%match_ip%& expansion condition"
11226 This condition matches an IP address to a list of IP address patterns. It must
11227 be followed by two argument strings. The first (after expansion) must be an IP
11228 address or an empty string. The second (not expanded) is a restricted host
11229 list that can match only an IP address, not a host name. For example:
11231 ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
11233 The specific types of host list item that are permitted in the list are:
11236 An IP address, optionally with a CIDR mask.
11238 A single asterisk, which matches any IP address.
11240 An empty item, which matches only if the IP address is empty. This could be
11241 useful for testing for a locally submitted message or one from specific hosts
11242 in a single test such as
11243 . ==== As this is a nested list, any displays it contains must be indented
11244 . ==== as otherwise they are too far to the left. This comment applies to
11245 . ==== the use of xmlto plus fop. There's no problem when formatting with
11246 . ==== sdop, with or without the extra indent.
11248 ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
11250 where the first item in the list is the empty string.
11252 The item @[] matches any of the local host's interface addresses.
11254 Single-key lookups are assumed to be like &"net-"& style lookups in host lists,
11255 even if &`net-`& is not specified. There is never any attempt to turn the IP
11256 address into a host name. The most common type of linear search for
11257 &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR
11258 masks. For example:
11260 ${if match_ip{$sender_host_address}{iplsearch;/some/file}...
11262 It is of course possible to use other kinds of lookup, and in such a case, you
11263 do need to specify the &`net-`& prefix if you want to specify a specific
11264 address mask, for example:
11266 ${if match_ip{$sender_host_address}{net24-dbm;/some/file}...
11268 However, unless you are combining a &%match_ip%& condition with others, it is
11269 just as easy to use the fact that a lookup is itself a condition, and write:
11271 ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}...
11275 Note that <&'string2'&> is not itself subject to string expansion, unless
11276 Exim was built with the EXPAND_LISTMATCH_RHS option.
11278 Consult section &<<SECThoslispatip>>& for further details of these patterns.
11280 .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
11281 .cindex "domain list" "in expansion condition"
11282 .cindex "address list" "in expansion condition"
11283 .cindex "local part" "list, in expansion condition"
11284 .cindex "&%match_local_part%& expansion condition"
11285 This condition, together with &%match_address%& and &%match_domain%&, make it
11286 possible to test domain, address, and local part lists within expansions. Each
11287 condition requires two arguments: an item and a list to match. A trivial
11290 ${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
11292 In each case, the second argument may contain any of the allowable items for a
11293 list of the appropriate type. Also, because the second argument
11294 is a standard form of list, it is possible to refer to a named list.
11295 Thus, you can use conditions like this:
11297 ${if match_domain{$domain}{+local_domains}{...
11299 .cindex "&`+caseful`&"
11300 For address lists, the matching starts off caselessly, but the &`+caseful`&
11301 item can be used, as in all address lists, to cause subsequent items to
11302 have their local parts matched casefully. Domains are always matched
11305 Note that <&'string2'&> is not itself subject to string expansion, unless
11306 Exim was built with the EXPAND_LISTMATCH_RHS option.
11308 &*Note*&: Host lists are &'not'& supported in this way. This is because
11309 hosts have two identities: a name and an IP address, and it is not clear
11310 how to specify cleanly how such a test would work. However, IP addresses can be
11311 matched using &%match_ip%&.
11313 .vitem &*pam&~{*&<&'string1'&>&*:*&<&'string2'&>&*:...}*&
11314 .cindex "PAM authentication"
11315 .cindex "AUTH" "with PAM"
11316 .cindex "Solaris" "PAM support"
11317 .cindex "expansion" "PAM authentication test"
11318 .cindex "&%pam%& expansion condition"
11319 &'Pluggable Authentication Modules'&
11320 (&url(http://www.kernel.org/pub/linux/libs/pam/)) are a facility that is
11321 available in the latest releases of Solaris and in some GNU/Linux
11322 distributions. The Exim support, which is intended for use in conjunction with
11323 the SMTP AUTH command, is available only if Exim is compiled with
11327 in &_Local/Makefile_&. You probably need to add &%-lpam%& to EXTRALIBS, and
11328 in some releases of GNU/Linux &%-ldl%& is also needed.
11330 The argument string is first expanded, and the result must be a
11331 colon-separated list of strings. Leading and trailing white space is ignored.
11332 The PAM module is initialized with the service name &"exim"& and the user name
11333 taken from the first item in the colon-separated data string (<&'string1'&>).
11334 The remaining items in the data string are passed over in response to requests
11335 from the authentication function. In the simple case there will only be one
11336 request, for a password, so the data consists of just two strings.
11338 There can be problems if any of the strings are permitted to contain colon
11339 characters. In the usual way, these have to be doubled to avoid being taken as
11340 separators. If the data is being inserted from a variable, the &%sg%& expansion
11341 item can be used to double any existing colons. For example, the configuration
11342 of a LOGIN authenticator might contain this setting:
11344 server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
11346 For a PLAIN authenticator you could use:
11348 server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
11350 In some operating systems, PAM authentication can be done only from a process
11351 running as root. Since Exim is running as the Exim user when receiving
11352 messages, this means that PAM cannot be used directly in those systems.
11353 A patched version of the &'pam_unix'& module that comes with the
11354 Linux PAM package is available from &url(http://www.e-admin.de/pam_exim/).
11355 The patched module allows one special uid/gid combination, in addition to root,
11356 to authenticate. If you build the patched module to allow the Exim user and
11357 group, PAM can then be used from an Exim authenticator.
11360 .vitem &*pwcheck&~{*&<&'string1'&>&*:*&<&'string2'&>&*}*&
11361 .cindex "&'pwcheck'& daemon"
11363 .cindex "expansion" "&'pwcheck'& authentication test"
11364 .cindex "&%pwcheck%& expansion condition"
11365 This condition supports user authentication using the Cyrus &'pwcheck'& daemon.
11366 This is one way of making it possible for passwords to be checked by a process
11367 that is not running as root. &*Note*&: The use of &'pwcheck'& is now
11368 deprecated. Its replacement is &'saslauthd'& (see below).
11370 The pwcheck support is not included in Exim by default. You need to specify
11371 the location of the pwcheck daemon's socket in &_Local/Makefile_& before
11372 building Exim. For example:
11374 CYRUS_PWCHECK_SOCKET=/var/pwcheck/pwcheck
11376 You do not need to install the full Cyrus software suite in order to use
11377 the pwcheck daemon. You can compile and install just the daemon alone
11378 from the Cyrus SASL library. Ensure that &'exim'& is the only user that has
11379 access to the &_/var/pwcheck_& directory.
11381 The &%pwcheck%& condition takes one argument, which must be the user name and
11382 password, separated by a colon. For example, in a LOGIN authenticator
11383 configuration, you might have this:
11385 server_condition = ${if pwcheck{$auth1:$auth2}}
11387 Again, for a PLAIN authenticator configuration, this would be:
11389 server_condition = ${if pwcheck{$auth2:$auth3}}
11391 .vitem &*queue_running*&
11392 .cindex "queue runner" "detecting when delivering from"
11393 .cindex "expansion" "queue runner test"
11394 .cindex "&%queue_running%& expansion condition"
11395 This condition, which has no data, is true during delivery attempts that are
11396 initiated by queue runner processes, and false otherwise.
11399 .vitem &*radius&~{*&<&'authentication&~string'&>&*}*&
11401 .cindex "expansion" "Radius authentication"
11402 .cindex "&%radius%& expansion condition"
11403 Radius authentication (RFC 2865) is supported in a similar way to PAM. You must
11404 set RADIUS_CONFIG_FILE in &_Local/Makefile_& to specify the location of
11405 the Radius client configuration file in order to build Exim with Radius
11408 With just that one setting, Exim expects to be linked with the &%radiusclient%&
11409 library, using the original API. If you are using release 0.4.0 or later of
11410 this library, you need to set
11412 RADIUS_LIB_TYPE=RADIUSCLIENTNEW
11414 in &_Local/Makefile_& when building Exim. You can also link Exim with the
11415 &%libradius%& library that comes with FreeBSD. To do this, set
11417 RADIUS_LIB_TYPE=RADLIB
11419 in &_Local/Makefile_&, in addition to setting RADIUS_CONFIGURE_FILE.
11420 You may also have to supply a suitable setting in EXTRALIBS so that the
11421 Radius library can be found when Exim is linked.
11423 The string specified by RADIUS_CONFIG_FILE is expanded and passed to the
11424 Radius client library, which calls the Radius server. The condition is true if
11425 the authentication is successful. For example:
11427 server_condition = ${if radius{<arguments>}}
11431 .vitem "&*saslauthd&~{{*&<&'user'&>&*}{*&<&'password'&>&*}&&&
11432 {*&<&'service'&>&*}{*&<&'realm'&>&*}}*&"
11433 .cindex "&'saslauthd'& daemon"
11435 .cindex "expansion" "&'saslauthd'& authentication test"
11436 .cindex "&%saslauthd%& expansion condition"
11437 This condition supports user authentication using the Cyrus &'saslauthd'&
11438 daemon. This replaces the older &'pwcheck'& daemon, which is now deprecated.
11439 Using this daemon is one way of making it possible for passwords to be checked
11440 by a process that is not running as root.
11442 The saslauthd support is not included in Exim by default. You need to specify
11443 the location of the saslauthd daemon's socket in &_Local/Makefile_& before
11444 building Exim. For example:
11446 CYRUS_SASLAUTHD_SOCKET=/var/state/saslauthd/mux
11448 You do not need to install the full Cyrus software suite in order to use
11449 the saslauthd daemon. You can compile and install just the daemon alone
11450 from the Cyrus SASL library.
11452 Up to four arguments can be supplied to the &%saslauthd%& condition, but only
11453 two are mandatory. For example:
11455 server_condition = ${if saslauthd{{$auth1}{$auth2}}}
11457 The service and the realm are optional (which is why the arguments are enclosed
11458 in their own set of braces). For details of the meaning of the service and
11459 realm, and how to run the daemon, consult the Cyrus documentation.
11464 .section "Combining expansion conditions" "SECID84"
11465 .cindex "expansion" "combining conditions"
11466 Several conditions can be tested at once by combining them using the &%and%&
11467 and &%or%& combination conditions. Note that &%and%& and &%or%& are complete
11468 conditions on their own, and precede their lists of sub-conditions. Each
11469 sub-condition must be enclosed in braces within the overall braces that contain
11470 the list. No repetition of &%if%& is used.
11474 .vitem &*or&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11475 .cindex "&""or""& expansion condition"
11476 .cindex "expansion" "&""or""& of conditions"
11477 The sub-conditions are evaluated from left to right. The condition is true if
11478 any one of the sub-conditions is true.
11481 ${if or {{eq{$local_part}{spqr}}{eq{$domain}{testing.com}}}...
11483 When a true sub-condition is found, the following ones are parsed but not
11484 evaluated. If there are several &"match"& sub-conditions the values of the
11485 numeric variables afterwards are taken from the first one that succeeds.
11487 .vitem &*and&~{{*&<&'cond1'&>&*}{*&<&'cond2'&>&*}...}*&
11488 .cindex "&""and""& expansion condition"
11489 .cindex "expansion" "&""and""& of conditions"
11490 The sub-conditions are evaluated from left to right. The condition is true if
11491 all of the sub-conditions are true. If there are several &"match"&
11492 sub-conditions, the values of the numeric variables afterwards are taken from
11493 the last one. When a false sub-condition is found, the following ones are
11494 parsed but not evaluated.
11496 .ecindex IIDexpcond
11501 .section "Expansion variables" "SECTexpvar"
11502 .cindex "expansion" "variables, list of"
11503 This section contains an alphabetical list of all the expansion variables. Some
11504 of them are available only when Exim is compiled with specific options such as
11505 support for TLS or the content scanning extension.
11508 .vitem "&$0$&, &$1$&, etc"
11509 .cindex "numerical variables (&$1$& &$2$& etc)"
11510 When a &%match%& expansion condition succeeds, these variables contain the
11511 captured substrings identified by the regular expression during subsequent
11512 processing of the success string of the containing &%if%& expansion item.
11513 In the expansion condition case
11514 they do not retain their values afterwards; in fact, their previous
11515 values are restored at the end of processing an &%if%& item. The numerical
11516 variables may also be set externally by some other matching process which
11517 precedes the expansion of the string. For example, the commands available in
11518 Exim filter files include an &%if%& command with its own regular expression
11519 matching condition.
11521 .vitem "&$acl_arg1$&, &$acl_arg2$&, etc"
11522 Within an acl condition, expansion condition or expansion item
11523 any arguments are copied to these variables,
11524 any unused variables being made empty.
11526 .vitem "&$acl_c...$&"
11527 Values can be placed in these variables by the &%set%& modifier in an ACL. They
11528 can be given any name that starts with &$acl_c$& and is at least six characters
11529 long, but the sixth character must be either a digit or an underscore. For
11530 example: &$acl_c5$&, &$acl_c_mycount$&. The values of the &$acl_c...$&
11531 variables persist throughout the lifetime of an SMTP connection. They can be
11532 used to pass information between ACLs and between different invocations of the
11533 same ACL. When a message is received, the values of these variables are saved
11534 with the message, and can be accessed by filters, routers, and transports
11535 during subsequent delivery.
11537 .vitem "&$acl_m...$&"
11538 These variables are like the &$acl_c...$& variables, except that their values
11539 are reset after a message has been received. Thus, if several messages are
11540 received in one SMTP connection, &$acl_m...$& values are not passed on from one
11541 message to the next, as &$acl_c...$& values are. The &$acl_m...$& variables are
11542 also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a
11543 message is received, the values of these variables are saved with the message,
11544 and can be accessed by filters, routers, and transports during subsequent
11547 .vitem &$acl_narg$&
11548 Within an acl condition, expansion condition or expansion item
11549 this variable has the number of arguments.
11551 .vitem &$acl_verify_message$&
11552 .vindex "&$acl_verify_message$&"
11553 After an address verification has failed, this variable contains the failure
11554 message. It retains its value for use in subsequent modifiers. The message can
11555 be preserved by coding like this:
11557 warn !verify = sender
11558 set acl_m0 = $acl_verify_message
11560 You can use &$acl_verify_message$& during the expansion of the &%message%& or
11561 &%log_message%& modifiers, to include information about the verification
11564 .vitem &$address_data$&
11565 .vindex "&$address_data$&"
11566 This variable is set by means of the &%address_data%& option in routers. The
11567 value then remains with the address while it is processed by subsequent routers
11568 and eventually a transport. If the transport is handling multiple addresses,
11569 the value from the first address is used. See chapter &<<CHAProutergeneric>>&
11570 for more details. &*Note*&: The contents of &$address_data$& are visible in
11573 If &$address_data$& is set when the routers are called from an ACL to verify
11574 a recipient address, the final value is still in the variable for subsequent
11575 conditions and modifiers of the ACL statement. If routing the address caused it
11576 to be redirected to just one address, the child address is also routed as part
11577 of the verification, and in this case the final value of &$address_data$& is
11578 from the child's routing.
11580 If &$address_data$& is set when the routers are called from an ACL to verify a
11581 sender address, the final value is also preserved, but this time in
11582 &$sender_address_data$&, to distinguish it from data from a recipient
11585 In both cases (recipient and sender verification), the value does not persist
11586 after the end of the current ACL statement. If you want to preserve
11587 these values for longer, you can save them in ACL variables.
11589 .vitem &$address_file$&
11590 .vindex "&$address_file$&"
11591 When, as a result of aliasing, forwarding, or filtering, a message is directed
11592 to a specific file, this variable holds the name of the file when the transport
11593 is running. At other times, the variable is empty. For example, using the
11594 default configuration, if user &%r2d2%& has a &_.forward_& file containing
11596 /home/r2d2/savemail
11598 then when the &(address_file)& transport is running, &$address_file$&
11599 contains the text string &`/home/r2d2/savemail`&.
11600 .cindex "Sieve filter" "value of &$address_file$&"
11601 For Sieve filters, the value may be &"inbox"& or a relative folder name. It is
11602 then up to the transport configuration to generate an appropriate absolute path
11603 to the relevant file.
11605 .vitem &$address_pipe$&
11606 .vindex "&$address_pipe$&"
11607 When, as a result of aliasing or forwarding, a message is directed to a pipe,
11608 this variable holds the pipe command when the transport is running.
11610 .vitem "&$auth1$& &-- &$auth3$&"
11611 .vindex "&$auth1$&, &$auth2$&, etc"
11612 These variables are used in SMTP authenticators (see chapters
11613 &<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
11615 .vitem &$authenticated_id$&
11616 .cindex "authentication" "id"
11617 .vindex "&$authenticated_id$&"
11618 When a server successfully authenticates a client it may be configured to
11619 preserve some of the authentication information in the variable
11620 &$authenticated_id$& (see chapter &<<CHAPSMTPAUTH>>&). For example, a
11621 user/password authenticator configuration might preserve the user name for use
11622 in the routers. Note that this is not the same information that is saved in
11623 &$sender_host_authenticated$&.
11625 When a message is submitted locally (that is, not over a TCP connection)
11626 the value of &$authenticated_id$& is normally the login name of the calling
11627 process. However, a trusted user can override this by means of the &%-oMai%&
11628 command line option.
11629 This second case also sets up inforamtion used by the
11630 &$authresults$& expansion item.
11632 .vitem &$authenticated_fail_id$&
11633 .cindex "authentication" "fail" "id"
11634 .vindex "&$authenticated_fail_id$&"
11635 When an authentication attempt fails, the variable &$authenticated_fail_id$&
11636 will contain the failed authentication id. If more than one authentication
11637 id is attempted, it will contain only the last one. The variable is
11638 available for processing in the ACL's, generally the quit or notquit ACL.
11639 A message to a local recipient could still be accepted without requiring
11640 authentication, which means this variable could also be visible in all of
11644 .vitem &$authenticated_sender$&
11645 .cindex "sender" "authenticated"
11646 .cindex "authentication" "sender"
11647 .cindex "AUTH" "on MAIL command"
11648 .vindex "&$authenticated_sender$&"
11649 When acting as a server, Exim takes note of the AUTH= parameter on an incoming
11650 SMTP MAIL command if it believes the sender is sufficiently trusted, as
11651 described in section &<<SECTauthparamail>>&. Unless the data is the string
11652 &"<>"&, it is set as the authenticated sender of the message, and the value is
11653 available during delivery in the &$authenticated_sender$& variable. If the
11654 sender is not trusted, Exim accepts the syntax of AUTH=, but ignores the data.
11656 .vindex "&$qualify_domain$&"
11657 When a message is submitted locally (that is, not over a TCP connection), the
11658 value of &$authenticated_sender$& is an address constructed from the login
11659 name of the calling process and &$qualify_domain$&, except that a trusted user
11660 can override this by means of the &%-oMas%& command line option.
11663 .vitem &$authentication_failed$&
11664 .cindex "authentication" "failure"
11665 .vindex "&$authentication_failed$&"
11666 This variable is set to &"1"& in an Exim server if a client issues an AUTH
11667 command that does not succeed. Otherwise it is set to &"0"&. This makes it
11668 possible to distinguish between &"did not try to authenticate"&
11669 (&$sender_host_authenticated$& is empty and &$authentication_failed$& is set to
11670 &"0"&) and &"tried to authenticate but failed"& (&$sender_host_authenticated$&
11671 is empty and &$authentication_failed$& is set to &"1"&). Failure includes any
11672 negative response to an AUTH command, including (for example) an attempt to use
11673 an undefined mechanism.
11675 .vitem &$av_failed$&
11676 .cindex "content scanning" "AV scanner failure"
11677 This variable is available when Exim is compiled with the content-scanning
11678 extension. It is set to &"0"& by default, but will be set to &"1"& if any
11679 problem occurs with the virus scanner (specified by &%av_scanner%&) during
11680 the ACL malware condition.
11682 .vitem &$body_linecount$&
11683 .cindex "message body" "line count"
11684 .cindex "body of message" "line count"
11685 .vindex "&$body_linecount$&"
11686 When a message is being received or delivered, this variable contains the
11687 number of lines in the message's body. See also &$message_linecount$&.
11689 .vitem &$body_zerocount$&
11690 .cindex "message body" "binary zero count"
11691 .cindex "body of message" "binary zero count"
11692 .cindex "binary zero" "in message body"
11693 .vindex "&$body_zerocount$&"
11694 When a message is being received or delivered, this variable contains the
11695 number of binary zero bytes (ASCII NULs) in the message's body.
11697 .vitem &$bounce_recipient$&
11698 .vindex "&$bounce_recipient$&"
11699 This is set to the recipient address of a bounce message while Exim is creating
11700 it. It is useful if a customized bounce message text file is in use (see
11701 chapter &<<CHAPemsgcust>>&).
11703 .vitem &$bounce_return_size_limit$&
11704 .vindex "&$bounce_return_size_limit$&"
11705 This contains the value set in the &%bounce_return_size_limit%& option, rounded
11706 up to a multiple of 1000. It is useful when a customized error message text
11707 file is in use (see chapter &<<CHAPemsgcust>>&).
11709 .vitem &$caller_gid$&
11710 .cindex "gid (group id)" "caller"
11711 .vindex "&$caller_gid$&"
11712 The real group id under which the process that called Exim was running. This is
11713 not the same as the group id of the originator of a message (see
11714 &$originator_gid$&). If Exim re-execs itself, this variable in the new
11715 incarnation normally contains the Exim gid.
11717 .vitem &$caller_uid$&
11718 .cindex "uid (user id)" "caller"
11719 .vindex "&$caller_uid$&"
11720 The real user id under which the process that called Exim was running. This is
11721 not the same as the user id of the originator of a message (see
11722 &$originator_uid$&). If Exim re-execs itself, this variable in the new
11723 incarnation normally contains the Exim uid.
11725 .vitem &$callout_address$&
11726 .vindex "&$callout_address$&"
11727 After a callout for verification, spamd or malware daemon service, the
11728 address that was connected to.
11730 .vitem &$compile_number$&
11731 .vindex "&$compile_number$&"
11732 The building process for Exim keeps a count of the number
11733 of times it has been compiled. This serves to distinguish different
11734 compilations of the same version of the program.
11736 .vitem &$config_dir$&
11737 .vindex "&$config_dir$&"
11738 The directory name of the main configuration file. That is, the content of
11739 &$config_file$& with the last component stripped. The value does not
11740 contain the trailing slash. If &$config_file$& does not contain a slash,
11741 &$config_dir$& is ".".
11743 .vitem &$config_file$&
11744 .vindex "&$config_file$&"
11745 The name of the main configuration file Exim is using.
11747 .vitem &$dkim_verify_status$&
11748 Results of DKIM verification.
11749 For details see section &<<SECDKIMVFY>>&.
11751 .vitem &$dkim_cur_signer$& &&&
11752 &$dkim_verify_reason$& &&&
11753 &$dkim_domain$& &&&
11754 &$dkim_identity$& &&&
11755 &$dkim_selector$& &&&
11757 &$dkim_canon_body$& &&&
11758 &$dkim_canon_headers$& &&&
11759 &$dkim_copiedheaders$& &&&
11760 &$dkim_bodylength$& &&&
11761 &$dkim_created$& &&&
11762 &$dkim_expires$& &&&
11763 &$dkim_headernames$& &&&
11764 &$dkim_key_testing$& &&&
11765 &$dkim_key_nosubdomains$& &&&
11766 &$dkim_key_srvtype$& &&&
11767 &$dkim_key_granularity$& &&&
11768 &$dkim_key_notes$& &&&
11769 &$dkim_key_length$&
11770 These variables are only available within the DKIM ACL.
11771 For details see section &<<SECDKIMVFY>>&.
11773 .vitem &$dkim_signers$&
11774 .vindex &$dkim_signers$&
11775 When a message has been received this variable contains
11776 a colon-separated list of signer domains and identities for the message.
11777 For details see section &<<SECDKIMVFY>>&.
11779 .vitem &$dnslist_domain$& &&&
11780 &$dnslist_matched$& &&&
11781 &$dnslist_text$& &&&
11783 .vindex "&$dnslist_domain$&"
11784 .vindex "&$dnslist_matched$&"
11785 .vindex "&$dnslist_text$&"
11786 .vindex "&$dnslist_value$&"
11787 .cindex "black list (DNS)"
11788 When a DNS (black) list lookup succeeds, these variables are set to contain
11789 the following data from the lookup: the list's domain name, the key that was
11790 looked up, the contents of any associated TXT record, and the value from the
11791 main A record. See section &<<SECID204>>& for more details.
11794 .vindex "&$domain$&"
11795 When an address is being routed, or delivered on its own, this variable
11796 contains the domain. Uppercase letters in the domain are converted into lower
11797 case for &$domain$&.
11799 Global address rewriting happens when a message is received, so the value of
11800 &$domain$& during routing and delivery is the value after rewriting. &$domain$&
11801 is set during user filtering, but not during system filtering, because a
11802 message may have many recipients and the system filter is called just once.
11804 When more than one address is being delivered at once (for example, several
11805 RCPT commands in one SMTP delivery), &$domain$& is set only if they all
11806 have the same domain. Transports can be restricted to handling only one domain
11807 at a time if the value of &$domain$& is required at transport time &-- this is
11808 the default for local transports. For further details of the environment in
11809 which local transports are run, see chapter &<<CHAPenvironment>>&.
11811 .oindex "&%delay_warning_condition%&"
11812 At the end of a delivery, if all deferred addresses have the same domain, it is
11813 set in &$domain$& during the expansion of &%delay_warning_condition%&.
11815 The &$domain$& variable is also used in some other circumstances:
11818 When an ACL is running for a RCPT command, &$domain$& contains the domain of
11819 the recipient address. The domain of the &'sender'& address is in
11820 &$sender_address_domain$& at both MAIL time and at RCPT time. &$domain$& is not
11821 normally set during the running of the MAIL ACL. However, if the sender address
11822 is verified with a callout during the MAIL ACL, the sender domain is placed in
11823 &$domain$& during the expansions of &%hosts%&, &%interface%&, and &%port%& in
11824 the &(smtp)& transport.
11827 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
11828 &$domain$& contains the domain portion of the address that is being rewritten;
11829 it can be used in the expansion of the replacement address, for example, to
11830 rewrite domains by file lookup.
11833 With one important exception, whenever a domain list is being scanned,
11834 &$domain$& contains the subject domain. &*Exception*&: When a domain list in
11835 a &%sender_domains%& condition in an ACL is being processed, the subject domain
11836 is in &$sender_address_domain$& and not in &$domain$&. It works this way so
11837 that, in a RCPT ACL, the sender domain list can be dependent on the
11838 recipient domain (which is what is in &$domain$& at this time).
11841 .cindex "ETRN" "value of &$domain$&"
11842 .oindex "&%smtp_etrn_command%&"
11843 When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains
11844 the complete argument of the ETRN command (see section &<<SECTETRN>>&).
11848 .vitem &$domain_data$&
11849 .vindex "&$domain_data$&"
11850 When the &%domains%& option on a router matches a domain by
11851 means of a lookup, the data read by the lookup is available during the running
11852 of the router as &$domain_data$&. In addition, if the driver routes the
11853 address to a transport, the value is available in that transport. If the
11854 transport is handling multiple addresses, the value from the first address is
11857 &$domain_data$& is also set when the &%domains%& condition in an ACL matches a
11858 domain by means of a lookup. The data read by the lookup is available during
11859 the rest of the ACL statement. In all other situations, this variable expands
11862 .vitem &$exim_gid$&
11863 .vindex "&$exim_gid$&"
11864 This variable contains the numerical value of the Exim group id.
11866 .vitem &$exim_path$&
11867 .vindex "&$exim_path$&"
11868 This variable contains the path to the Exim binary.
11870 .vitem &$exim_uid$&
11871 .vindex "&$exim_uid$&"
11872 This variable contains the numerical value of the Exim user id.
11874 .vitem &$exim_version$&
11875 .vindex "&$exim_version$&"
11876 This variable contains the version string of the Exim build.
11877 The first character is a major version number, currently 4.
11878 Then after a dot, the next group of digits is a minor version number.
11879 There may be other characters following the minor version.
11881 .vitem &$header_$&<&'name'&>
11882 This is not strictly an expansion variable. It is expansion syntax for
11883 inserting the message header line with the given name. Note that the name must
11884 be terminated by colon or white space, because it may contain a wide variety of
11885 characters. Note also that braces must &'not'& be used.
11887 .vitem &$headers_added$&
11888 .vindex "&$headers_added$&"
11889 Within an ACL this variable contains the headers added so far by
11890 the ACL modifier add_header (section &<<SECTaddheadacl>>&).
11891 The headers are a newline-separated list.
11895 When the &%check_local_user%& option is set for a router, the user's home
11896 directory is placed in &$home$& when the check succeeds. In particular, this
11897 means it is set during the running of users' filter files. A router may also
11898 explicitly set a home directory for use by a transport; this can be overridden
11899 by a setting on the transport itself.
11901 When running a filter test via the &%-bf%& option, &$home$& is set to the value
11902 of the environment variable HOME, which is subject to the
11903 &%keep_environment%& and &%add_environment%& main config options.
11907 If a router assigns an address to a transport (any transport), and passes a
11908 list of hosts with the address, the value of &$host$& when the transport starts
11909 to run is the name of the first host on the list. Note that this applies both
11910 to local and remote transports.
11912 .cindex "transport" "filter"
11913 .cindex "filter" "transport filter"
11914 For the &(smtp)& transport, if there is more than one host, the value of
11915 &$host$& changes as the transport works its way through the list. In
11916 particular, when the &(smtp)& transport is expanding its options for encryption
11917 using TLS, or for specifying a transport filter (see chapter
11918 &<<CHAPtransportgeneric>>&), &$host$& contains the name of the host to which it
11921 When used in the client part of an authenticator configuration (see chapter
11922 &<<CHAPSMTPAUTH>>&), &$host$& contains the name of the server to which the
11923 client is connected.
11926 .vitem &$host_address$&
11927 .vindex "&$host_address$&"
11928 This variable is set to the remote host's IP address whenever &$host$& is set
11929 for a remote connection. It is also set to the IP address that is being checked
11930 when the &%ignore_target_hosts%& option is being processed.
11932 .vitem &$host_data$&
11933 .vindex "&$host_data$&"
11934 If a &%hosts%& condition in an ACL is satisfied by means of a lookup, the
11935 result of the lookup is made available in the &$host_data$& variable. This
11936 allows you, for example, to do things like this:
11938 deny hosts = net-lsearch;/some/file
11939 message = $host_data
11941 .vitem &$host_lookup_deferred$&
11942 .cindex "host name" "lookup, failure of"
11943 .vindex "&$host_lookup_deferred$&"
11944 This variable normally contains &"0"&, as does &$host_lookup_failed$&. When a
11945 message comes from a remote host and there is an attempt to look up the host's
11946 name from its IP address, and the attempt is not successful, one of these
11947 variables is set to &"1"&.
11950 If the lookup receives a definite negative response (for example, a DNS lookup
11951 succeeded, but no records were found), &$host_lookup_failed$& is set to &"1"&.
11954 If there is any kind of problem during the lookup, such that Exim cannot
11955 tell whether or not the host name is defined (for example, a timeout for a DNS
11956 lookup), &$host_lookup_deferred$& is set to &"1"&.
11959 Looking up a host's name from its IP address consists of more than just a
11960 single reverse lookup. Exim checks that a forward lookup of at least one of the
11961 names it receives from a reverse lookup yields the original IP address. If this
11962 is not the case, Exim does not accept the looked up name(s), and
11963 &$host_lookup_failed$& is set to &"1"&. Thus, being able to find a name from an
11964 IP address (for example, the existence of a PTR record in the DNS) is not
11965 sufficient on its own for the success of a host name lookup. If the reverse
11966 lookup succeeds, but there is a lookup problem such as a timeout when checking
11967 the result, the name is not accepted, and &$host_lookup_deferred$& is set to
11968 &"1"&. See also &$sender_host_name$&.
11970 .cindex authentication "expansion item"
11971 Performing these checks sets up information used by the
11972 &$authresults$& expansion item.
11975 .vitem &$host_lookup_failed$&
11976 .vindex "&$host_lookup_failed$&"
11977 See &$host_lookup_deferred$&.
11979 .vitem &$host_port$&
11980 .vindex "&$host_port$&"
11981 This variable is set to the remote host's TCP port whenever &$host$& is set
11982 for an outbound connection.
11984 .vitem &$initial_cwd$&
11985 .vindex "&$initial_cwd$&
11986 This variable contains the full path name of the initial working
11987 directory of the current Exim process. This may differ from the current
11988 working directory, as Exim changes this to "/" during early startup, and
11989 to &$spool_directory$& later.
11992 .vindex "&$inode$&"
11993 The only time this variable is set is while expanding the &%directory_file%&
11994 option in the &(appendfile)& transport. The variable contains the inode number
11995 of the temporary file which is about to be renamed. It can be used to construct
11996 a unique name for the file.
11998 .vitem &$interface_address$&
11999 .vindex "&$interface_address$&"
12000 This is an obsolete name for &$received_ip_address$&.
12002 .vitem &$interface_port$&
12003 .vindex "&$interface_port$&"
12004 This is an obsolete name for &$received_port$&.
12008 This variable is used during the expansion of &*forall*& and &*forany*&
12009 conditions (see section &<<SECTexpcond>>&), and &*filter*&, &*map*&, and
12010 &*reduce*& items (see section &<<SECTexpcond>>&). In other circumstances, it is
12014 .vindex "&$ldap_dn$&"
12015 This variable, which is available only when Exim is compiled with LDAP support,
12016 contains the DN from the last entry in the most recently successful LDAP
12019 .vitem &$load_average$&
12020 .vindex "&$load_average$&"
12021 This variable contains the system load average, multiplied by 1000 so that it
12022 is an integer. For example, if the load average is 0.21, the value of the
12023 variable is 210. The value is recomputed every time the variable is referenced.
12025 .vitem &$local_part$&
12026 .vindex "&$local_part$&"
12027 When an address is being routed, or delivered on its own, this
12028 variable contains the local part. When a number of addresses are being
12029 delivered together (for example, multiple RCPT commands in an SMTP
12030 session), &$local_part$& is not set.
12032 Global address rewriting happens when a message is received, so the value of
12033 &$local_part$& during routing and delivery is the value after rewriting.
12034 &$local_part$& is set during user filtering, but not during system filtering,
12035 because a message may have many recipients and the system filter is called just
12038 .vindex "&$local_part_prefix$&"
12039 .vindex "&$local_part_suffix$&"
12040 If a local part prefix or suffix has been recognized, it is not included in the
12041 value of &$local_part$& during routing and subsequent delivery. The values of
12042 any prefix or suffix are in &$local_part_prefix$& and
12043 &$local_part_suffix$&, respectively.
12045 When a message is being delivered to a file, pipe, or autoreply transport as a
12046 result of aliasing or forwarding, &$local_part$& is set to the local part of
12047 the parent address, not to the file name or command (see &$address_file$& and
12050 When an ACL is running for a RCPT command, &$local_part$& contains the
12051 local part of the recipient address.
12053 When a rewrite item is being processed (see chapter &<<CHAPrewrite>>&),
12054 &$local_part$& contains the local part of the address that is being rewritten;
12055 it can be used in the expansion of the replacement address, for example.
12057 In all cases, all quoting is removed from the local part. For example, for both
12060 "abc:xyz"@test.example
12061 abc\:xyz@test.example
12063 the value of &$local_part$& is
12067 If you use &$local_part$& to create another address, you should always wrap it
12068 inside a quoting operator. For example, in a &(redirect)& router you could
12071 data = ${quote_local_part:$local_part}@new.domain.example
12073 &*Note*&: The value of &$local_part$& is normally lower cased. If you want
12074 to process local parts in a case-dependent manner in a router, you can set the
12075 &%caseful_local_part%& option (see chapter &<<CHAProutergeneric>>&).
12077 .vitem &$local_part_data$&
12078 .vindex "&$local_part_data$&"
12079 When the &%local_parts%& option on a router matches a local part by means of a
12080 lookup, the data read by the lookup is available during the running of the
12081 router as &$local_part_data$&. In addition, if the driver routes the address
12082 to a transport, the value is available in that transport. If the transport is
12083 handling multiple addresses, the value from the first address is used.
12085 &$local_part_data$& is also set when the &%local_parts%& condition in an ACL
12086 matches a local part by means of a lookup. The data read by the lookup is
12087 available during the rest of the ACL statement. In all other situations, this
12088 variable expands to nothing.
12090 .vitem &$local_part_prefix$&
12091 .vindex "&$local_part_prefix$&"
12092 When an address is being routed or delivered, and a
12093 specific prefix for the local part was recognized, it is available in this
12094 variable, having been removed from &$local_part$&.
12096 .vitem &$local_part_suffix$&
12097 .vindex "&$local_part_suffix$&"
12098 When an address is being routed or delivered, and a
12099 specific suffix for the local part was recognized, it is available in this
12100 variable, having been removed from &$local_part$&.
12102 .vitem &$local_scan_data$&
12103 .vindex "&$local_scan_data$&"
12104 This variable contains the text returned by the &[local_scan()]& function when
12105 a message is received. See chapter &<<CHAPlocalscan>>& for more details.
12107 .vitem &$local_user_gid$&
12108 .vindex "&$local_user_gid$&"
12109 See &$local_user_uid$&.
12111 .vitem &$local_user_uid$&
12112 .vindex "&$local_user_uid$&"
12113 This variable and &$local_user_gid$& are set to the uid and gid after the
12114 &%check_local_user%& router precondition succeeds. This means that their values
12115 are available for the remaining preconditions (&%senders%&, &%require_files%&,
12116 and &%condition%&), for the &%address_data%& expansion, and for any
12117 router-specific expansions. At all other times, the values in these variables
12118 are &`(uid_t)(-1)`& and &`(gid_t)(-1)`&, respectively.
12120 .vitem &$localhost_number$&
12121 .vindex "&$localhost_number$&"
12122 This contains the expanded value of the
12123 &%localhost_number%& option. The expansion happens after the main options have
12126 .vitem &$log_inodes$&
12127 .vindex "&$log_inodes$&"
12128 The number of free inodes in the disk partition where Exim's
12129 log files are being written. The value is recalculated whenever the variable is
12130 referenced. If the relevant file system does not have the concept of inodes,
12131 the value of is -1. See also the &%check_log_inodes%& option.
12133 .vitem &$log_space$&
12134 .vindex "&$log_space$&"
12135 The amount of free space (as a number of kilobytes) in the disk
12136 partition where Exim's log files are being written. The value is recalculated
12137 whenever the variable is referenced. If the operating system does not have the
12138 ability to find the amount of free space (only true for experimental systems),
12139 the space value is -1. See also the &%check_log_space%& option.
12142 .vitem &$lookup_dnssec_authenticated$&
12143 .vindex "&$lookup_dnssec_authenticated$&"
12144 This variable is set after a DNS lookup done by
12145 a dnsdb lookup expansion, dnslookup router or smtp transport.
12146 .cindex "DNS" "DNSSEC"
12147 It will be empty if &(DNSSEC)& was not requested,
12148 &"no"& if the result was not labelled as authenticated data
12149 and &"yes"& if it was.
12150 Results that are labelled as authoritative answer that match
12151 the &%dns_trust_aa%& configuration variable count also
12152 as authenticated data.
12154 .vitem &$mailstore_basename$&
12155 .vindex "&$mailstore_basename$&"
12156 This variable is set only when doing deliveries in &"mailstore"& format in the
12157 &(appendfile)& transport. During the expansion of the &%mailstore_prefix%&,
12158 &%mailstore_suffix%&, &%message_prefix%&, and &%message_suffix%& options, it
12159 contains the basename of the files that are being written, that is, the name
12160 without the &".tmp"&, &".env"&, or &".msg"& suffix. At all other times, this
12163 .vitem &$malware_name$&
12164 .vindex "&$malware_name$&"
12165 This variable is available when Exim is compiled with the
12166 content-scanning extension. It is set to the name of the virus that was found
12167 when the ACL &%malware%& condition is true (see section &<<SECTscanvirus>>&).
12169 .vitem &$max_received_linelength$&
12170 .vindex "&$max_received_linelength$&"
12171 .cindex "maximum" "line length"
12172 .cindex "line length" "maximum"
12173 This variable contains the number of bytes in the longest line that was
12174 received as part of the message, not counting the line termination
12176 It is not valid if the &%spool_files_wireformat%& option is used.
12178 .vitem &$message_age$&
12179 .cindex "message" "age of"
12180 .vindex "&$message_age$&"
12181 This variable is set at the start of a delivery attempt to contain the number
12182 of seconds since the message was received. It does not change during a single
12185 .vitem &$message_body$&
12186 .cindex "body of message" "expansion variable"
12187 .cindex "message body" "in expansion"
12188 .cindex "binary zero" "in message body"
12189 .vindex "&$message_body$&"
12190 .oindex "&%message_body_visible%&"
12191 This variable contains the initial portion of a message's body while it is
12192 being delivered, and is intended mainly for use in filter files. The maximum
12193 number of characters of the body that are put into the variable is set by the
12194 &%message_body_visible%& configuration option; the default is 500.
12196 .oindex "&%message_body_newlines%&"
12197 By default, newlines are converted into spaces in &$message_body$&, to make it
12198 easier to search for phrases that might be split over a line break. However,
12199 this can be disabled by setting &%message_body_newlines%& to be true. Binary
12200 zeros are always converted into spaces.
12202 .vitem &$message_body_end$&
12203 .cindex "body of message" "expansion variable"
12204 .cindex "message body" "in expansion"
12205 .vindex "&$message_body_end$&"
12206 This variable contains the final portion of a message's
12207 body while it is being delivered. The format and maximum size are as for
12210 .vitem &$message_body_size$&
12211 .cindex "body of message" "size"
12212 .cindex "message body" "size"
12213 .vindex "&$message_body_size$&"
12214 When a message is being delivered, this variable contains the size of the body
12215 in bytes. The count starts from the character after the blank line that
12216 separates the body from the header. Newlines are included in the count. See
12217 also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
12219 If the spool file is wireformat
12220 (see the &%spool_files_wireformat%& main option)
12221 the CRLF line-terminators are included in the count.
12223 .vitem &$message_exim_id$&
12224 .vindex "&$message_exim_id$&"
12225 When a message is being received or delivered, this variable contains the
12226 unique message id that is generated and used by Exim to identify the message.
12227 An id is not created for a message until after its header has been successfully
12228 received. &*Note*&: This is &'not'& the contents of the &'Message-ID:'& header
12229 line; it is the local id that Exim assigns to the message, for example:
12230 &`1BXTIK-0001yO-VA`&.
12232 .vitem &$message_headers$&
12233 .vindex &$message_headers$&
12234 This variable contains a concatenation of all the header lines when a message
12235 is being processed, except for lines added by routers or transports. The header
12236 lines are separated by newline characters. Their contents are decoded in the
12237 same way as a header line that is inserted by &%bheader%&.
12239 .vitem &$message_headers_raw$&
12240 .vindex &$message_headers_raw$&
12241 This variable is like &$message_headers$& except that no processing of the
12242 contents of header lines is done.
12244 .vitem &$message_id$&
12245 This is an old name for &$message_exim_id$&. It is now deprecated.
12247 .vitem &$message_linecount$&
12248 .vindex "&$message_linecount$&"
12249 This variable contains the total number of lines in the header and body of the
12250 message. Compare &$body_linecount$&, which is the count for the body only.
12251 During the DATA and content-scanning ACLs, &$message_linecount$& contains the
12252 number of lines received. Before delivery happens (that is, before filters,
12253 routers, and transports run) the count is increased to include the
12254 &'Received:'& header line that Exim standardly adds, and also any other header
12255 lines that are added by ACLs. The blank line that separates the message header
12256 from the body is not counted.
12258 As with the special case of &$message_size$&, during the expansion of the
12259 appendfile transport's maildir_tag option in maildir format, the value of
12260 &$message_linecount$& is the precise size of the number of newlines in the
12261 file that has been written (minus one for the blank line between the
12262 header and the body).
12264 Here is an example of the use of this variable in a DATA ACL:
12266 deny message = Too many lines in message header
12268 ${if <{250}{${eval:$message_linecount - $body_linecount}}}
12270 In the MAIL and RCPT ACLs, the value is zero because at that stage the
12271 message has not yet been received.
12273 This variable is not valid if the &%spool_files_wireformat%& option is used.
12275 .vitem &$message_size$&
12276 .cindex "size" "of message"
12277 .cindex "message" "size"
12278 .vindex "&$message_size$&"
12279 When a message is being processed, this variable contains its size in bytes. In
12280 most cases, the size includes those headers that were received with the
12281 message, but not those (such as &'Envelope-to:'&) that are added to individual
12282 deliveries as they are written. However, there is one special case: during the
12283 expansion of the &%maildir_tag%& option in the &(appendfile)& transport while
12284 doing a delivery in maildir format, the value of &$message_size$& is the
12285 precise size of the file that has been written. See also
12286 &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&.
12288 .cindex "RCPT" "value of &$message_size$&"
12289 While running a per message ACL (mail/rcpt/predata), &$message_size$&
12290 contains the size supplied on the MAIL command, or -1 if no size was given. The
12291 value may not, of course, be truthful.
12293 .vitem &$mime_$&&'xxx'&
12294 A number of variables whose names start with &$mime$& are
12295 available when Exim is compiled with the content-scanning extension. For
12296 details, see section &<<SECTscanmimepart>>&.
12298 .vitem "&$n0$& &-- &$n9$&"
12299 These variables are counters that can be incremented by means
12300 of the &%add%& command in filter files.
12302 .vitem &$original_domain$&
12303 .vindex "&$domain$&"
12304 .vindex "&$original_domain$&"
12305 When a top-level address is being processed for delivery, this contains the
12306 same value as &$domain$&. However, if a &"child"& address (for example,
12307 generated by an alias, forward, or filter file) is being processed, this
12308 variable contains the domain of the original address (lower cased). This
12309 differs from &$parent_domain$& only when there is more than one level of
12310 aliasing or forwarding. When more than one address is being delivered in a
12311 single transport run, &$original_domain$& is not set.
12313 If a new address is created by means of a &%deliver%& command in a system
12314 filter, it is set up with an artificial &"parent"& address. This has the local
12315 part &'system-filter'& and the default qualify domain.
12317 .vitem &$original_local_part$&
12318 .vindex "&$local_part$&"
12319 .vindex "&$original_local_part$&"
12320 When a top-level address is being processed for delivery, this contains the
12321 same value as &$local_part$&, unless a prefix or suffix was removed from the
12322 local part, because &$original_local_part$& always contains the full local
12323 part. When a &"child"& address (for example, generated by an alias, forward, or
12324 filter file) is being processed, this variable contains the full local part of
12325 the original address.
12327 If the router that did the redirection processed the local part
12328 case-insensitively, the value in &$original_local_part$& is in lower case.
12329 This variable differs from &$parent_local_part$& only when there is more than
12330 one level of aliasing or forwarding. When more than one address is being
12331 delivered in a single transport run, &$original_local_part$& is not set.
12333 If a new address is created by means of a &%deliver%& command in a system
12334 filter, it is set up with an artificial &"parent"& address. This has the local
12335 part &'system-filter'& and the default qualify domain.
12337 .vitem &$originator_gid$&
12338 .cindex "gid (group id)" "of originating user"
12339 .cindex "sender" "gid"
12340 .vindex "&$caller_gid$&"
12341 .vindex "&$originator_gid$&"
12342 This variable contains the value of &$caller_gid$& that was set when the
12343 message was received. For messages received via the command line, this is the
12344 gid of the sending user. For messages received by SMTP over TCP/IP, this is
12345 normally the gid of the Exim user.
12347 .vitem &$originator_uid$&
12348 .cindex "uid (user id)" "of originating user"
12349 .cindex "sender" "uid"
12350 .vindex "&$caller_uid$&"
12351 .vindex "&$originator_uid$&"
12352 The value of &$caller_uid$& that was set when the message was received. For
12353 messages received via the command line, this is the uid of the sending user.
12354 For messages received by SMTP over TCP/IP, this is normally the uid of the Exim
12357 .vitem &$parent_domain$&
12358 .vindex "&$parent_domain$&"
12359 This variable is similar to &$original_domain$& (see
12360 above), except that it refers to the immediately preceding parent address.
12362 .vitem &$parent_local_part$&
12363 .vindex "&$parent_local_part$&"
12364 This variable is similar to &$original_local_part$&
12365 (see above), except that it refers to the immediately preceding parent address.
12368 .cindex "pid (process id)" "of current process"
12370 This variable contains the current process id.
12372 .vitem &$pipe_addresses$&
12373 .cindex "filter" "transport filter"
12374 .cindex "transport" "filter"
12375 .vindex "&$pipe_addresses$&"
12376 This is not an expansion variable, but is mentioned here because the string
12377 &`$pipe_addresses`& is handled specially in the command specification for the
12378 &(pipe)& transport (chapter &<<CHAPpipetransport>>&) and in transport filters
12379 (described under &%transport_filter%& in chapter &<<CHAPtransportgeneric>>&).
12380 It cannot be used in general expansion strings, and provokes an &"unknown
12381 variable"& error if encountered.
12383 .vitem &$primary_hostname$&
12384 .vindex "&$primary_hostname$&"
12385 This variable contains the value set by &%primary_hostname%& in the
12386 configuration file, or read by the &[uname()]& function. If &[uname()]& returns
12387 a single-component name, Exim calls &[gethostbyname()]& (or
12388 &[getipnodebyname()]& where available) in an attempt to acquire a fully
12389 qualified host name. See also &$smtp_active_hostname$&.
12392 .vitem &$proxy_external_address$& &&&
12393 &$proxy_external_port$& &&&
12394 &$proxy_local_address$& &&&
12395 &$proxy_local_port$& &&&
12397 These variables are only available when built with Proxy Protocol
12399 For details see chapter &<<SECTproxyInbound>>&.
12401 .vitem &$prdr_requested$&
12402 .cindex "PRDR" "variable for"
12403 This variable is set to &"yes"& if PRDR was requested by the client for the
12404 current message, otherwise &"no"&.
12406 .vitem &$prvscheck_address$&
12407 This variable is used in conjunction with the &%prvscheck%& expansion item,
12408 which is described in sections &<<SECTexpansionitems>>& and
12409 &<<SECTverifyPRVS>>&.
12411 .vitem &$prvscheck_keynum$&
12412 This variable is used in conjunction with the &%prvscheck%& expansion item,
12413 which is described in sections &<<SECTexpansionitems>>& and
12414 &<<SECTverifyPRVS>>&.
12416 .vitem &$prvscheck_result$&
12417 This variable is used in conjunction with the &%prvscheck%& expansion item,
12418 which is described in sections &<<SECTexpansionitems>>& and
12419 &<<SECTverifyPRVS>>&.
12421 .vitem &$qualify_domain$&
12422 .vindex "&$qualify_domain$&"
12423 The value set for the &%qualify_domain%& option in the configuration file.
12425 .vitem &$qualify_recipient$&
12426 .vindex "&$qualify_recipient$&"
12427 The value set for the &%qualify_recipient%& option in the configuration file,
12428 or if not set, the value of &$qualify_domain$&.
12430 .vitem &$queue_name$&
12431 .vindex &$queue_name$&
12432 .cindex "named queues"
12433 .cindex queues named
12434 The name of the spool queue in use; empty for the default queue.
12436 .vitem &$rcpt_count$&
12437 .vindex "&$rcpt_count$&"
12438 When a message is being received by SMTP, this variable contains the number of
12439 RCPT commands received for the current message. If this variable is used in a
12440 RCPT ACL, its value includes the current command.
12442 .vitem &$rcpt_defer_count$&
12443 .vindex "&$rcpt_defer_count$&"
12444 .cindex "4&'xx'& responses" "count of"
12445 When a message is being received by SMTP, this variable contains the number of
12446 RCPT commands in the current message that have previously been rejected with a
12447 temporary (4&'xx'&) response.
12449 .vitem &$rcpt_fail_count$&
12450 .vindex "&$rcpt_fail_count$&"
12451 When a message is being received by SMTP, this variable contains the number of
12452 RCPT commands in the current message that have previously been rejected with a
12453 permanent (5&'xx'&) response.
12455 .vitem &$received_count$&
12456 .vindex "&$received_count$&"
12457 This variable contains the number of &'Received:'& header lines in the message,
12458 including the one added by Exim (so its value is always greater than zero). It
12459 is available in the DATA ACL, the non-SMTP ACL, and while routing and
12462 .vitem &$received_for$&
12463 .vindex "&$received_for$&"
12464 If there is only a single recipient address in an incoming message, this
12465 variable contains that address when the &'Received:'& header line is being
12466 built. The value is copied after recipient rewriting has happened, but before
12467 the &[local_scan()]& function is run.
12469 .vitem &$received_ip_address$&
12470 .vindex "&$received_ip_address$&"
12471 As soon as an Exim server starts processing an incoming TCP/IP connection, this
12472 variable is set to the address of the local IP interface, and &$received_port$&
12473 is set to the local port number. (The remote IP address and port are in
12474 &$sender_host_address$& and &$sender_host_port$&.) When testing with &%-bh%&,
12475 the port value is -1 unless it has been set using the &%-oMi%& command line
12478 As well as being useful in ACLs (including the &"connect"& ACL), these variable
12479 could be used, for example, to make the file name for a TLS certificate depend
12480 on which interface and/or port is being used for the incoming connection. The
12481 values of &$received_ip_address$& and &$received_port$& are saved with any
12482 messages that are received, thus making these variables available at delivery
12484 For outbound connections see &$sending_ip_address$&.
12486 .vitem &$received_port$&
12487 .vindex "&$received_port$&"
12488 See &$received_ip_address$&.
12490 .vitem &$received_protocol$&
12491 .vindex "&$received_protocol$&"
12492 When a message is being processed, this variable contains the name of the
12493 protocol by which it was received. Most of the names used by Exim are defined
12494 by RFCs 821, 2821, and 3848. They start with &"smtp"& (the client used HELO) or
12495 &"esmtp"& (the client used EHLO). This can be followed by &"s"& for secure
12496 (encrypted) and/or &"a"& for authenticated. Thus, for example, if the protocol
12497 is set to &"esmtpsa"&, the message was received over an encrypted SMTP
12498 connection and the client was successfully authenticated.
12500 Exim uses the protocol name &"smtps"& for the case when encryption is
12501 automatically set up on connection without the use of STARTTLS (see
12502 &%tls_on_connect_ports%&), and the client uses HELO to initiate the
12503 encrypted SMTP session. The name &"smtps"& is also used for the rare situation
12504 where the client initially uses EHLO, sets up an encrypted connection using
12505 STARTTLS, and then uses HELO afterwards.
12507 The &%-oMr%& option provides a way of specifying a custom protocol name for
12508 messages that are injected locally by trusted callers. This is commonly used to
12509 identify messages that are being re-injected after some kind of scanning.
12511 .vitem &$received_time$&
12512 .vindex "&$received_time$&"
12513 This variable contains the date and time when the current message was received,
12514 as a number of seconds since the start of the Unix epoch.
12516 .vitem &$recipient_data$&
12517 .vindex "&$recipient_data$&"
12518 This variable is set after an indexing lookup success in an ACL &%recipients%&
12519 condition. It contains the data from the lookup, and the value remains set
12520 until the next &%recipients%& test. Thus, you can do things like this:
12522 &`require recipients = cdb*@;/some/file`&
12523 &`deny `&&'some further test involving'& &`$recipient_data`&
12525 &*Warning*&: This variable is set only when a lookup is used as an indexing
12526 method in the address list, using the semicolon syntax as in the example above.
12527 The variable is not set for a lookup that is used as part of the string
12528 expansion that all such lists undergo before being interpreted.
12530 .vitem &$recipient_verify_failure$&
12531 .vindex "&$recipient_verify_failure$&"
12532 In an ACL, when a recipient verification fails, this variable contains
12533 information about the failure. It is set to one of the following words:
12536 &"qualify"&: The address was unqualified (no domain), and the message
12537 was neither local nor came from an exempted host.
12540 &"route"&: Routing failed.
12543 &"mail"&: Routing succeeded, and a callout was attempted; rejection occurred at
12544 or before the MAIL command (that is, on initial connection, HELO, or
12548 &"recipient"&: The RCPT command in a callout was rejected.
12551 &"postmaster"&: The postmaster check in a callout was rejected.
12554 The main use of this variable is expected to be to distinguish between
12555 rejections of MAIL and rejections of RCPT.
12557 .vitem &$recipients$&
12558 .vindex "&$recipients$&"
12559 This variable contains a list of envelope recipients for a message. A comma and
12560 a space separate the addresses in the replacement text. However, the variable
12561 is not generally available, to prevent exposure of Bcc recipients in
12562 unprivileged users' filter files. You can use &$recipients$& only in these
12566 In a system filter file.
12568 In the ACLs associated with the DATA command and with non-SMTP messages, that
12569 is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&,
12570 &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and
12571 &%acl_not_smtp_mime%&.
12573 From within a &[local_scan()]& function.
12577 .vitem &$recipients_count$&
12578 .vindex "&$recipients_count$&"
12579 When a message is being processed, this variable contains the number of
12580 envelope recipients that came with the message. Duplicates are not excluded
12581 from the count. While a message is being received over SMTP, the number
12582 increases for each accepted recipient. It can be referenced in an ACL.
12585 .vitem &$regex_match_string$&
12586 .vindex "&$regex_match_string$&"
12587 This variable is set to contain the matching regular expression after a
12588 &%regex%& ACL condition has matched (see section &<<SECTscanregex>>&).
12590 .vitem "&$regex1$&, &$regex2$&, etc"
12591 .cindex "regex submatch variables (&$1regex$& &$2regex$& etc)"
12592 When a &%regex%& or &%mime_regex%& ACL condition succeeds,
12593 these variables contain the
12594 captured substrings identified by the regular expression.
12597 .vitem &$reply_address$&
12598 .vindex "&$reply_address$&"
12599 When a message is being processed, this variable contains the contents of the
12600 &'Reply-To:'& header line if one exists and it is not empty, or otherwise the
12601 contents of the &'From:'& header line. Apart from the removal of leading
12602 white space, the value is not processed in any way. In particular, no RFC 2047
12603 decoding or character code translation takes place.
12605 .vitem &$return_path$&
12606 .vindex "&$return_path$&"
12607 When a message is being delivered, this variable contains the return path &--
12608 the sender field that will be sent as part of the envelope. It is not enclosed
12609 in <> characters. At the start of routing an address, &$return_path$& has the
12610 same value as &$sender_address$&, but if, for example, an incoming message to a
12611 mailing list has been expanded by a router which specifies a different address
12612 for bounce messages, &$return_path$& subsequently contains the new bounce
12613 address, whereas &$sender_address$& always contains the original sender address
12614 that was received with the message. In other words, &$sender_address$& contains
12615 the incoming envelope sender, and &$return_path$& contains the outgoing
12618 .vitem &$return_size_limit$&
12619 .vindex "&$return_size_limit$&"
12620 This is an obsolete name for &$bounce_return_size_limit$&.
12622 .vitem &$router_name$&
12623 .cindex "router" "name"
12624 .cindex "name" "of router"
12625 .vindex "&$router_name$&"
12626 During the running of a router this variable contains its name.
12629 .cindex "return code" "from &%run%& expansion"
12630 .vindex "&$runrc$&"
12631 This variable contains the return code from a command that is run by the
12632 &%${run...}%& expansion item. &*Warning*&: In a router or transport, you cannot
12633 assume the order in which option values are expanded, except for those
12634 preconditions whose order of testing is documented. Therefore, you cannot
12635 reliably expect to set &$runrc$& by the expansion of one option, and use it in
12638 .vitem &$self_hostname$&
12639 .oindex "&%self%&" "value of host name"
12640 .vindex "&$self_hostname$&"
12641 When an address is routed to a supposedly remote host that turns out to be the
12642 local host, what happens is controlled by the &%self%& generic router option.
12643 One of its values causes the address to be passed to another router. When this
12644 happens, &$self_hostname$& is set to the name of the local host that the
12645 original router encountered. In other circumstances its contents are null.
12647 .vitem &$sender_address$&
12648 .vindex "&$sender_address$&"
12649 When a message is being processed, this variable contains the sender's address
12650 that was received in the message's envelope. The case of letters in the address
12651 is retained, in both the local part and the domain. For bounce messages, the
12652 value of this variable is the empty string. See also &$return_path$&.
12654 .vitem &$sender_address_data$&
12655 .vindex "&$address_data$&"
12656 .vindex "&$sender_address_data$&"
12657 If &$address_data$& is set when the routers are called from an ACL to verify a
12658 sender address, the final value is preserved in &$sender_address_data$&, to
12659 distinguish it from data from a recipient address. The value does not persist
12660 after the end of the current ACL statement. If you want to preserve it for
12661 longer, you can save it in an ACL variable.
12663 .vitem &$sender_address_domain$&
12664 .vindex "&$sender_address_domain$&"
12665 The domain portion of &$sender_address$&.
12667 .vitem &$sender_address_local_part$&
12668 .vindex "&$sender_address_local_part$&"
12669 The local part portion of &$sender_address$&.
12671 .vitem &$sender_data$&
12672 .vindex "&$sender_data$&"
12673 This variable is set after a lookup success in an ACL &%senders%& condition or
12674 in a router &%senders%& option. It contains the data from the lookup, and the
12675 value remains set until the next &%senders%& test. Thus, you can do things like
12678 &`require senders = cdb*@;/some/file`&
12679 &`deny `&&'some further test involving'& &`$sender_data`&
12681 &*Warning*&: This variable is set only when a lookup is used as an indexing
12682 method in the address list, using the semicolon syntax as in the example above.
12683 The variable is not set for a lookup that is used as part of the string
12684 expansion that all such lists undergo before being interpreted.
12686 .vitem &$sender_fullhost$&
12687 .vindex "&$sender_fullhost$&"
12688 When a message is received from a remote host, this variable contains the host
12689 name and IP address in a single string. It ends with the IP address in square
12690 brackets, followed by a colon and a port number if the logging of ports is
12691 enabled. The format of the rest of the string depends on whether the host
12692 issued a HELO or EHLO SMTP command, and whether the host name was verified by
12693 looking up its IP address. (Looking up the IP address can be forced by the
12694 &%host_lookup%& option, independent of verification.) A plain host name at the
12695 start of the string is a verified host name; if this is not present,
12696 verification either failed or was not requested. A host name in parentheses is
12697 the argument of a HELO or EHLO command. This is omitted if it is identical to
12698 the verified host name or to the host's IP address in square brackets.
12700 .vitem &$sender_helo_dnssec$&
12701 .vindex "&$sender_helo_dnssec$&"
12702 This boolean variable is true if a successful HELO verification was
12703 .cindex "DNS" "DNSSEC"
12704 done using DNS information the resolver library stated was authenticated data.
12706 .vitem &$sender_helo_name$&
12707 .vindex "&$sender_helo_name$&"
12708 When a message is received from a remote host that has issued a HELO or EHLO
12709 command, the argument of that command is placed in this variable. It is also
12710 set if HELO or EHLO is used when a message is received using SMTP locally via
12711 the &%-bs%& or &%-bS%& options.
12713 .vitem &$sender_host_address$&
12714 .vindex "&$sender_host_address$&"
12715 When a message is received from a remote host using SMTP,
12716 this variable contains that
12717 host's IP address. For locally non-SMTP submitted messages, it is empty.
12719 .vitem &$sender_host_authenticated$&
12720 .vindex "&$sender_host_authenticated$&"
12721 This variable contains the name (not the public name) of the authenticator
12722 driver that successfully authenticated the client from which the message was
12723 received. It is empty if there was no successful authentication. See also
12724 &$authenticated_id$&.
12726 .vitem &$sender_host_dnssec$&
12727 .vindex "&$sender_host_dnssec$&"
12728 If an attempt to populate &$sender_host_name$& has been made
12729 (by reference, &%hosts_lookup%& or
12730 otherwise) then this boolean will have been set true if, and only if, the
12731 resolver library states that both
12732 the reverse and forward DNS were authenticated data. At all
12733 other times, this variable is false.
12735 .cindex "DNS" "DNSSEC"
12736 It is likely that you will need to coerce DNSSEC support on in the resolver
12737 library, by setting:
12742 Exim does not perform DNSSEC validation itself, instead leaving that to a
12743 validating resolver (e.g. unbound, or bind with suitable configuration).
12745 If you have changed &%host_lookup_order%& so that &`bydns`& is not the first
12746 mechanism in the list, then this variable will be false.
12748 This requires that your system resolver library support EDNS0 (and that
12749 DNSSEC flags exist in the system headers). If the resolver silently drops
12750 all EDNS0 options, then this will have no effect. OpenBSD's asr resolver
12751 is known to currently ignore EDNS0, documented in CAVEATS of asr_run(3).
12754 .vitem &$sender_host_name$&
12755 .vindex "&$sender_host_name$&"
12756 When a message is received from a remote host, this variable contains the
12757 host's name as obtained by looking up its IP address. For messages received by
12758 other means, this variable is empty.
12760 .vindex "&$host_lookup_failed$&"
12761 If the host name has not previously been looked up, a reference to
12762 &$sender_host_name$& triggers a lookup (for messages from remote hosts).
12763 A looked up name is accepted only if it leads back to the original IP address
12764 via a forward lookup. If either the reverse or the forward lookup fails to find
12765 any data, or if the forward lookup does not yield the original IP address,
12766 &$sender_host_name$& remains empty, and &$host_lookup_failed$& is set to &"1"&.
12768 .vindex "&$host_lookup_deferred$&"
12769 However, if either of the lookups cannot be completed (for example, there is a
12770 DNS timeout), &$host_lookup_deferred$& is set to &"1"&, and
12771 &$host_lookup_failed$& remains set to &"0"&.
12773 Once &$host_lookup_failed$& is set to &"1"&, Exim does not try to look up the
12774 host name again if there is a subsequent reference to &$sender_host_name$&
12775 in the same Exim process, but it does try again if &$host_lookup_deferred$&
12778 Exim does not automatically look up every calling host's name. If you want
12779 maximum efficiency, you should arrange your configuration so that it avoids
12780 these lookups altogether. The lookup happens only if one or more of the
12781 following are true:
12784 A string containing &$sender_host_name$& is expanded.
12786 The calling host matches the list in &%host_lookup%&. In the default
12787 configuration, this option is set to *, so it must be changed if lookups are
12788 to be avoided. (In the code, the default for &%host_lookup%& is unset.)
12790 Exim needs the host name in order to test an item in a host list. The items
12791 that require this are described in sections &<<SECThoslispatnam>>& and
12792 &<<SECThoslispatnamsk>>&.
12794 The calling host matches &%helo_try_verify_hosts%& or &%helo_verify_hosts%&.
12795 In this case, the host name is required to compare with the name quoted in any
12796 EHLO or HELO commands that the client issues.
12798 The remote host issues a EHLO or HELO command that quotes one of the
12799 domains in &%helo_lookup_domains%&. The default value of this option is
12800 . ==== As this is a nested list, any displays it contains must be indented
12801 . ==== as otherwise they are too far to the left.
12803 helo_lookup_domains = @ : @[]
12805 which causes a lookup if a remote host (incorrectly) gives the server's name or
12806 IP address in an EHLO or HELO command.
12810 .vitem &$sender_host_port$&
12811 .vindex "&$sender_host_port$&"
12812 When a message is received from a remote host, this variable contains the port
12813 number that was used on the remote host.
12815 .vitem &$sender_ident$&
12816 .vindex "&$sender_ident$&"
12817 When a message is received from a remote host, this variable contains the
12818 identification received in response to an RFC 1413 request. When a message has
12819 been received locally, this variable contains the login name of the user that
12822 .vitem &$sender_rate_$&&'xxx'&
12823 A number of variables whose names begin &$sender_rate_$& are set as part of the
12824 &%ratelimit%& ACL condition. Details are given in section
12825 &<<SECTratelimiting>>&.
12827 .vitem &$sender_rcvhost$&
12828 .cindex "DNS" "reverse lookup"
12829 .cindex "reverse DNS lookup"
12830 .vindex "&$sender_rcvhost$&"
12831 This is provided specifically for use in &'Received:'& headers. It starts with
12832 either the verified host name (as obtained from a reverse DNS lookup) or, if
12833 there is no verified host name, the IP address in square brackets. After that
12834 there may be text in parentheses. When the first item is a verified host name,
12835 the first thing in the parentheses is the IP address in square brackets,
12836 followed by a colon and a port number if port logging is enabled. When the
12837 first item is an IP address, the port is recorded as &"port=&'xxxx'&"& inside
12840 There may also be items of the form &"helo=&'xxxx'&"& if HELO or EHLO
12841 was used and its argument was not identical to the real host name or IP
12842 address, and &"ident=&'xxxx'&"& if an RFC 1413 ident string is available. If
12843 all three items are present in the parentheses, a newline and tab are inserted
12844 into the string, to improve the formatting of the &'Received:'& header.
12846 .vitem &$sender_verify_failure$&
12847 .vindex "&$sender_verify_failure$&"
12848 In an ACL, when a sender verification fails, this variable contains information
12849 about the failure. The details are the same as for
12850 &$recipient_verify_failure$&.
12852 .vitem &$sending_ip_address$&
12853 .vindex "&$sending_ip_address$&"
12854 This variable is set whenever an outgoing SMTP connection to another host has
12855 been set up. It contains the IP address of the local interface that is being
12856 used. This is useful if a host that has more than one IP address wants to take
12857 on different personalities depending on which one is being used. For incoming
12858 connections, see &$received_ip_address$&.
12860 .vitem &$sending_port$&
12861 .vindex "&$sending_port$&"
12862 This variable is set whenever an outgoing SMTP connection to another host has
12863 been set up. It contains the local port that is being used. For incoming
12864 connections, see &$received_port$&.
12866 .vitem &$smtp_active_hostname$&
12867 .vindex "&$smtp_active_hostname$&"
12868 During an incoming SMTP session, this variable contains the value of the active
12869 host name, as specified by the &%smtp_active_hostname%& option. The value of
12870 &$smtp_active_hostname$& is saved with any message that is received, so its
12871 value can be consulted during routing and delivery.
12873 .vitem &$smtp_command$&
12874 .vindex "&$smtp_command$&"
12875 During the processing of an incoming SMTP command, this variable contains the
12876 entire command. This makes it possible to distinguish between HELO and EHLO in
12877 the HELO ACL, and also to distinguish between commands such as these:
12882 For a MAIL command, extra parameters such as SIZE can be inspected. For a RCPT
12883 command, the address in &$smtp_command$& is the original address before any
12884 rewriting, whereas the values in &$local_part$& and &$domain$& are taken from
12885 the address after SMTP-time rewriting.
12887 .vitem &$smtp_command_argument$&
12888 .cindex "SMTP" "command, argument for"
12889 .vindex "&$smtp_command_argument$&"
12890 While an ACL is running to check an SMTP command, this variable contains the
12891 argument, that is, the text that follows the command name, with leading white
12892 space removed. Following the introduction of &$smtp_command$&, this variable is
12893 somewhat redundant, but is retained for backwards compatibility.
12895 .vitem &$smtp_command_history$&
12896 .cindex SMTP "command history"
12897 .vindex "&$smtp_command_history$&"
12898 A comma-separated list (with no whitespace) of the most-recent SMTP commands
12899 received, in time-order left to right. Only a limited number of commands
12902 .vitem &$smtp_count_at_connection_start$&
12903 .vindex "&$smtp_count_at_connection_start$&"
12904 This variable is set greater than zero only in processes spawned by the Exim
12905 daemon for handling incoming SMTP connections. The name is deliberately long,
12906 in order to emphasize what the contents are. When the daemon accepts a new
12907 connection, it increments this variable. A copy of the variable is passed to
12908 the child process that handles the connection, but its value is fixed, and
12909 never changes. It is only an approximation of how many incoming connections
12910 there actually are, because many other connections may come and go while a
12911 single connection is being processed. When a child process terminates, the
12912 daemon decrements its copy of the variable.
12914 .vitem "&$sn0$& &-- &$sn9$&"
12915 These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators
12916 that were current at the end of the system filter file. This allows a system
12917 filter file to set values that can be tested in users' filter files. For
12918 example, a system filter could set a value indicating how likely it is that a
12919 message is junk mail.
12921 .vitem &$spam_$&&'xxx'&
12922 A number of variables whose names start with &$spam$& are available when Exim
12923 is compiled with the content-scanning extension. For details, see section
12924 &<<SECTscanspamass>>&.
12926 .vitem &$spf_header_comment$& &&&
12927 &$spf_received$& &&&
12929 &$spf_result_guessed$& &&&
12930 &$spf_smtp_comment$&
12931 These variables are only available if Exim is built with SPF support.
12932 For details see section &<<SECSPF>>&.
12934 .vitem &$spool_directory$&
12935 .vindex "&$spool_directory$&"
12936 The name of Exim's spool directory.
12938 .vitem &$spool_inodes$&
12939 .vindex "&$spool_inodes$&"
12940 The number of free inodes in the disk partition where Exim's spool files are
12941 being written. The value is recalculated whenever the variable is referenced.
12942 If the relevant file system does not have the concept of inodes, the value of
12943 is -1. See also the &%check_spool_inodes%& option.
12945 .vitem &$spool_space$&
12946 .vindex "&$spool_space$&"
12947 The amount of free space (as a number of kilobytes) in the disk partition where
12948 Exim's spool files are being written. The value is recalculated whenever the
12949 variable is referenced. If the operating system does not have the ability to
12950 find the amount of free space (only true for experimental systems), the space
12951 value is -1. For example, to check in an ACL that there is at least 50
12952 megabytes free on the spool, you could write:
12954 condition = ${if > {$spool_space}{50000}}
12956 See also the &%check_spool_space%& option.
12959 .vitem &$thisaddress$&
12960 .vindex "&$thisaddress$&"
12961 This variable is set only during the processing of the &%foranyaddress%&
12962 command in a filter file. Its use is explained in the description of that
12963 command, which can be found in the separate document entitled &'Exim's
12964 interfaces to mail filtering'&.
12966 .vitem &$tls_in_bits$&
12967 .vindex "&$tls_in_bits$&"
12968 Contains an approximation of the TLS cipher's bit-strength
12969 on the inbound connection; the meaning of
12970 this depends upon the TLS implementation used.
12971 If TLS has not been negotiated, the value will be 0.
12972 The value of this is automatically fed into the Cyrus SASL authenticator
12973 when acting as a server, to specify the "external SSF" (a SASL term).
12975 The deprecated &$tls_bits$& variable refers to the inbound side
12976 except when used in the context of an outbound SMTP delivery, when it refers to
12979 .vitem &$tls_out_bits$&
12980 .vindex "&$tls_out_bits$&"
12981 Contains an approximation of the TLS cipher's bit-strength
12982 on an outbound SMTP connection; the meaning of
12983 this depends upon the TLS implementation used.
12984 If TLS has not been negotiated, the value will be 0.
12986 .vitem &$tls_in_ourcert$&
12987 .vindex "&$tls_in_ourcert$&"
12988 .cindex certificate variables
12989 This variable refers to the certificate presented to the peer of an
12990 inbound connection when the message was received.
12991 It is only useful as the argument of a
12992 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
12993 or a &%def%& condition.
12995 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
12996 when a list of more than one
12997 file is used for &%tls_certificate%&, this variable is not reliable.
12999 .vitem &$tls_in_peercert$&
13000 .vindex "&$tls_in_peercert$&"
13001 This variable refers to the certificate presented by the peer of an
13002 inbound connection when the message was received.
13003 It is only useful as the argument of a
13004 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13005 or a &%def%& condition.
13006 If certificate verification fails it may refer to a failing chain element
13007 which is not the leaf.
13009 .vitem &$tls_out_ourcert$&
13010 .vindex "&$tls_out_ourcert$&"
13011 This variable refers to the certificate presented to the peer of an
13012 outbound connection. It is only useful as the argument of a
13013 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13014 or a &%def%& condition.
13016 .vitem &$tls_out_peercert$&
13017 .vindex "&$tls_out_peercert$&"
13018 This variable refers to the certificate presented by the peer of an
13019 outbound connection. It is only useful as the argument of a
13020 &%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
13021 or a &%def%& condition.
13022 If certificate verification fails it may refer to a failing chain element
13023 which is not the leaf.
13025 .vitem &$tls_in_certificate_verified$&
13026 .vindex "&$tls_in_certificate_verified$&"
13027 This variable is set to &"1"& if a TLS certificate was verified when the
13028 message was received, and &"0"& otherwise.
13030 The deprecated &$tls_certificate_verified$& variable refers to the inbound side
13031 except when used in the context of an outbound SMTP delivery, when it refers to
13034 .vitem &$tls_out_certificate_verified$&
13035 .vindex "&$tls_out_certificate_verified$&"
13036 This variable is set to &"1"& if a TLS certificate was verified when an
13037 outbound SMTP connection was made,
13038 and &"0"& otherwise.
13040 .vitem &$tls_in_cipher$&
13041 .vindex "&$tls_in_cipher$&"
13042 .vindex "&$tls_cipher$&"
13043 When a message is received from a remote host over an encrypted SMTP
13044 connection, this variable is set to the cipher suite that was negotiated, for
13045 example DES-CBC3-SHA. In other circumstances, in particular, for message
13046 received over unencrypted connections, the variable is empty. Testing
13047 &$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and
13048 non-encrypted connections during ACL processing.
13050 The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception,
13051 but in the context of an outward SMTP delivery taking place via the &(smtp)& transport
13052 becomes the same as &$tls_out_cipher$&.
13054 .vitem &$tls_out_cipher$&
13055 .vindex "&$tls_out_cipher$&"
13057 cleared before any outgoing SMTP connection is made,
13058 and then set to the outgoing cipher suite if one is negotiated. See chapter
13059 &<<CHAPTLS>>& for details of TLS support and chapter &<<CHAPsmtptrans>>& for
13060 details of the &(smtp)& transport.
13062 .vitem &$tls_out_dane$&
13063 .vindex &$tls_out_dane$&
13064 DANE active status. See section &<<SECDANE>>&.
13066 .vitem &$tls_in_ocsp$&
13067 .vindex "&$tls_in_ocsp$&"
13068 When a message is received from a remote client connection
13069 the result of any OCSP request from the client is encoded in this variable:
13071 0 OCSP proof was not requested (default value)
13072 1 No response to request
13073 2 Response not verified
13074 3 Verification failed
13075 4 Verification succeeded
13078 .vitem &$tls_out_ocsp$&
13079 .vindex "&$tls_out_ocsp$&"
13080 When a message is sent to a remote host connection
13081 the result of any OCSP request made is encoded in this variable.
13082 See &$tls_in_ocsp$& for values.
13084 .vitem &$tls_in_peerdn$&
13085 .vindex "&$tls_in_peerdn$&"
13086 .vindex "&$tls_peerdn$&"
13087 .cindex certificate "extracting fields"
13088 When a message is received from a remote host over an encrypted SMTP
13089 connection, and Exim is configured to request a certificate from the client,
13090 the value of the Distinguished Name of the certificate is made available in the
13091 &$tls_in_peerdn$& during subsequent processing.
13092 If certificate verification fails it may refer to a failing chain element
13093 which is not the leaf.
13095 The deprecated &$tls_peerdn$& variable refers to the inbound side
13096 except when used in the context of an outbound SMTP delivery, when it refers to
13099 .vitem &$tls_out_peerdn$&
13100 .vindex "&$tls_out_peerdn$&"
13101 When a message is being delivered to a remote host over an encrypted SMTP
13102 connection, and Exim is configured to request a certificate from the server,
13103 the value of the Distinguished Name of the certificate is made available in the
13104 &$tls_out_peerdn$& during subsequent processing.
13105 If certificate verification fails it may refer to a failing chain element
13106 which is not the leaf.
13108 .vitem &$tls_in_sni$&
13109 .vindex "&$tls_in_sni$&"
13110 .vindex "&$tls_sni$&"
13111 .cindex "TLS" "Server Name Indication"
13112 When a TLS session is being established, if the client sends the Server
13113 Name Indication extension, the value will be placed in this variable.
13114 If the variable appears in &%tls_certificate%& then this option and
13115 some others, described in &<<SECTtlssni>>&,
13116 will be re-expanded early in the TLS session, to permit
13117 a different certificate to be presented (and optionally a different key to be
13118 used) to the client, based upon the value of the SNI extension.
13120 The deprecated &$tls_sni$& variable refers to the inbound side
13121 except when used in the context of an outbound SMTP delivery, when it refers to
13124 .vitem &$tls_out_sni$&
13125 .vindex "&$tls_out_sni$&"
13126 .cindex "TLS" "Server Name Indication"
13128 SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
13131 .vitem &$tls_out_tlsa_usage$&
13132 .vindex &$tls_out_tlsa_usage$&
13133 Bitfield of TLSA record types found. See section &<<SECDANE>>&.
13135 .vitem &$tod_bsdinbox$&
13136 .vindex "&$tod_bsdinbox$&"
13137 The time of day and the date, in the format required for BSD-style mailbox
13138 files, for example: Thu Oct 17 17:14:09 1995.
13140 .vitem &$tod_epoch$&
13141 .vindex "&$tod_epoch$&"
13142 The time and date as a number of seconds since the start of the Unix epoch.
13144 .vitem &$tod_epoch_l$&
13145 .vindex "&$tod_epoch_l$&"
13146 The time and date as a number of microseconds since the start of the Unix epoch.
13148 .vitem &$tod_full$&
13149 .vindex "&$tod_full$&"
13150 A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40
13151 +0100. The timezone is always given as a numerical offset from UTC, with
13152 positive values used for timezones that are ahead (east) of UTC, and negative
13153 values for those that are behind (west).
13156 .vindex "&$tod_log$&"
13157 The time and date in the format used for writing Exim's log files, for example:
13158 1995-10-12 15:32:29, but without a timezone.
13160 .vitem &$tod_logfile$&
13161 .vindex "&$tod_logfile$&"
13162 This variable contains the date in the format yyyymmdd. This is the format that
13163 is used for datestamping log files when &%log_file_path%& contains the &`%D`&
13166 .vitem &$tod_zone$&
13167 .vindex "&$tod_zone$&"
13168 This variable contains the numerical value of the local timezone, for example:
13171 .vitem &$tod_zulu$&
13172 .vindex "&$tod_zulu$&"
13173 This variable contains the UTC date and time in &"Zulu"& format, as specified
13174 by ISO 8601, for example: 20030221154023Z.
13176 .vitem &$transport_name$&
13177 .cindex "transport" "name"
13178 .cindex "name" "of transport"
13179 .vindex "&$transport_name$&"
13180 During the running of a transport, this variable contains its name.
13183 .vindex "&$value$&"
13184 This variable contains the result of an expansion lookup, extraction operation,
13185 or external command, as described above. It is also used during a
13186 &*reduce*& expansion.
13188 .vitem &$verify_mode$&
13189 .vindex "&$verify_mode$&"
13190 While a router or transport is being run in verify mode or for cutthrough delivery,
13191 contains "S" for sender-verification or "R" for recipient-verification.
13194 .vitem &$version_number$&
13195 .vindex "&$version_number$&"
13196 The version number of Exim.
13198 .vitem &$warn_message_delay$&
13199 .vindex "&$warn_message_delay$&"
13200 This variable is set only during the creation of a message warning about a
13201 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13203 .vitem &$warn_message_recipients$&
13204 .vindex "&$warn_message_recipients$&"
13205 This variable is set only during the creation of a message warning about a
13206 delivery delay. Details of its use are explained in section &<<SECTcustwarn>>&.
13212 . ////////////////////////////////////////////////////////////////////////////
13213 . ////////////////////////////////////////////////////////////////////////////
13215 .chapter "Embedded Perl" "CHAPperl"
13216 .scindex IIDperl "Perl" "calling from Exim"
13217 Exim can be built to include an embedded Perl interpreter. When this is done,
13218 Perl subroutines can be called as part of the string expansion process. To make
13219 use of the Perl support, you need version 5.004 or later of Perl installed on
13220 your system. To include the embedded interpreter in the Exim binary, include
13225 in your &_Local/Makefile_& and then build Exim in the normal way.
13228 .section "Setting up so Perl can be used" "SECID85"
13229 .oindex "&%perl_startup%&"
13230 Access to Perl subroutines is via a global configuration option called
13231 &%perl_startup%& and an expansion string operator &%${perl ...}%&. If there is
13232 no &%perl_startup%& option in the Exim configuration file then no Perl
13233 interpreter is started and there is almost no overhead for Exim (since none of
13234 the Perl library will be paged in unless used). If there is a &%perl_startup%&
13235 option then the associated value is taken to be Perl code which is executed in
13236 a newly created Perl interpreter.
13238 The value of &%perl_startup%& is not expanded in the Exim sense, so you do not
13239 need backslashes before any characters to escape special meanings. The option
13240 should usually be something like
13242 perl_startup = do '/etc/exim.pl'
13244 where &_/etc/exim.pl_& is Perl code which defines any subroutines you want to
13245 use from Exim. Exim can be configured either to start up a Perl interpreter as
13246 soon as it is entered, or to wait until the first time it is needed. Starting
13247 the interpreter at the beginning ensures that it is done while Exim still has
13248 its setuid privilege, but can impose an unnecessary overhead if Perl is not in
13249 fact used in a particular run. Also, note that this does not mean that Exim is
13250 necessarily running as root when Perl is called at a later time. By default,
13251 the interpreter is started only when it is needed, but this can be changed in
13255 .oindex "&%perl_at_start%&"
13256 Setting &%perl_at_start%& (a boolean option) in the configuration requests
13257 a startup when Exim is entered.
13259 The command line option &%-ps%& also requests a startup when Exim is entered,
13260 overriding the setting of &%perl_at_start%&.
13263 There is also a command line option &%-pd%& (for delay) which suppresses the
13264 initial startup, even if &%perl_at_start%& is set.
13267 .oindex "&%perl_taintmode%&"
13268 .cindex "Perl" "taintmode"
13269 To provide more security executing Perl code via the embedded Perl
13270 interpreter, the &%perl_taintmode%& option can be set. This enables the
13271 taint mode of the Perl interpreter. You are encouraged to set this
13272 option to a true value. To avoid breaking existing installations, it
13276 .section "Calling Perl subroutines" "SECID86"
13277 When the configuration file includes a &%perl_startup%& option you can make use
13278 of the string expansion item to call the Perl subroutines that are defined
13279 by the &%perl_startup%& code. The operator is used in any of the following
13283 ${perl{foo}{argument}}
13284 ${perl{foo}{argument1}{argument2} ... }
13286 which calls the subroutine &%foo%& with the given arguments. A maximum of eight
13287 arguments may be passed. Passing more than this results in an expansion failure
13288 with an error message of the form
13290 Too many arguments passed to Perl subroutine "foo" (max is 8)
13292 The return value of the Perl subroutine is evaluated in a scalar context before
13293 it is passed back to Exim to be inserted into the expanded string. If the
13294 return value is &'undef'&, the expansion is forced to fail in the same way as
13295 an explicit &"fail"& on an &%if%& or &%lookup%& item. If the subroutine aborts
13296 by obeying Perl's &%die%& function, the expansion fails with the error message
13297 that was passed to &%die%&.
13300 .section "Calling Exim functions from Perl" "SECID87"
13301 Within any Perl code called from Exim, the function &'Exim::expand_string()'&
13302 is available to call back into Exim's string expansion function. For example,
13305 my $lp = Exim::expand_string('$local_part');
13307 makes the current Exim &$local_part$& available in the Perl variable &$lp$&.
13308 Note those are single quotes and not double quotes to protect against
13309 &$local_part$& being interpolated as a Perl variable.
13311 If the string expansion is forced to fail by a &"fail"& item, the result of
13312 &'Exim::expand_string()'& is &%undef%&. If there is a syntax error in the
13313 expansion string, the Perl call from the original expansion string fails with
13314 an appropriate error message, in the same way as if &%die%& were used.
13316 .cindex "debugging" "from embedded Perl"
13317 .cindex "log" "writing from embedded Perl"
13318 Two other Exim functions are available for use from within Perl code.
13319 &'Exim::debug_write()'& writes a string to the standard error stream if Exim's
13320 debugging is enabled. If you want a newline at the end, you must supply it.
13321 &'Exim::log_write()'& writes a string to Exim's main log, adding a leading
13322 timestamp. In this case, you should not supply a terminating newline.
13325 .section "Use of standard output and error by Perl" "SECID88"
13326 .cindex "Perl" "standard output and error"
13327 You should not write to the standard error or output streams from within your
13328 Perl code, as it is not defined how these are set up. In versions of Exim
13329 before 4.50, it is possible for the standard output or error to refer to the
13330 SMTP connection during message reception via the daemon. Writing to this stream
13331 is certain to cause chaos. From Exim 4.50 onwards, the standard output and
13332 error streams are connected to &_/dev/null_& in the daemon. The chaos is
13333 avoided, but the output is lost.
13335 .cindex "Perl" "use of &%warn%&"
13336 The Perl &%warn%& statement writes to the standard error stream by default.
13337 Calls to &%warn%& may be embedded in Perl modules that you use, but over which
13338 you have no control. When Exim starts up the Perl interpreter, it arranges for
13339 output from the &%warn%& statement to be written to the Exim main log. You can
13340 change this by including appropriate Perl magic somewhere in your Perl code.
13341 For example, to discard &%warn%& output completely, you need this:
13343 $SIG{__WARN__} = sub { };
13345 Whenever a &%warn%& is obeyed, the anonymous subroutine is called. In this
13346 example, the code for the subroutine is empty, so it does nothing, but you can
13347 include any Perl code that you like. The text of the &%warn%& message is passed
13348 as the first subroutine argument.
13352 . ////////////////////////////////////////////////////////////////////////////
13353 . ////////////////////////////////////////////////////////////////////////////
13355 .chapter "Starting the daemon and the use of network interfaces" &&&
13356 "CHAPinterfaces" &&&
13357 "Starting the daemon"
13358 .cindex "daemon" "starting"
13359 .cindex "interface" "listening"
13360 .cindex "network interface"
13361 .cindex "interface" "network"
13362 .cindex "IP address" "for listening"
13363 .cindex "daemon" "listening IP addresses"
13364 .cindex "TCP/IP" "setting listening interfaces"
13365 .cindex "TCP/IP" "setting listening ports"
13366 A host that is connected to a TCP/IP network may have one or more physical
13367 hardware network interfaces. Each of these interfaces may be configured as one
13368 or more &"logical"& interfaces, which are the entities that a program actually
13369 works with. Each of these logical interfaces is associated with an IP address.
13370 In addition, TCP/IP software supports &"loopback"& interfaces (127.0.0.1 in
13371 IPv4 and ::1 in IPv6), which do not use any physical hardware. Exim requires
13372 knowledge about the host's interfaces for use in three different circumstances:
13375 When a listening daemon is started, Exim needs to know which interfaces
13376 and ports to listen on.
13378 When Exim is routing an address, it needs to know which IP addresses
13379 are associated with local interfaces. This is required for the correct
13380 processing of MX lists by removing the local host and others with the
13381 same or higher priority values. Also, Exim needs to detect cases
13382 when an address is routed to an IP address that in fact belongs to the
13383 local host. Unless the &%self%& router option or the &%allow_localhost%&
13384 option of the smtp transport is set (as appropriate), this is treated
13385 as an error situation.
13387 When Exim connects to a remote host, it may need to know which interface to use
13388 for the outgoing connection.
13392 Exim's default behaviour is likely to be appropriate in the vast majority
13393 of cases. If your host has only one interface, and you want all its IP
13394 addresses to be treated in the same way, and you are using only the
13395 standard SMTP port, you should not need to take any special action. The
13396 rest of this chapter does not apply to you.
13398 In a more complicated situation you may want to listen only on certain
13399 interfaces, or on different ports, and for this reason there are a number of
13400 options that can be used to influence Exim's behaviour. The rest of this
13401 chapter describes how they operate.
13403 When a message is received over TCP/IP, the interface and port that were
13404 actually used are set in &$received_ip_address$& and &$received_port$&.
13408 .section "Starting a listening daemon" "SECID89"
13409 When a listening daemon is started (by means of the &%-bd%& command line
13410 option), the interfaces and ports on which it listens are controlled by the
13414 &%daemon_smtp_ports%& contains a list of default ports
13416 (For backward compatibility, this option can also be specified in the singular.)
13418 &%local_interfaces%& contains list of interface IP addresses on which to
13419 listen. Each item may optionally also specify a port.
13422 The default list separator in both cases is a colon, but this can be changed as
13423 described in section &<<SECTlistconstruct>>&. When IPv6 addresses are involved,
13424 it is usually best to change the separator to avoid having to double all the
13425 colons. For example:
13427 local_interfaces = <; 127.0.0.1 ; \
13430 3ffe:ffff:836f::fe86:a061
13432 There are two different formats for specifying a port along with an IP address
13433 in &%local_interfaces%&:
13436 The port is added onto the address with a dot separator. For example, to listen
13437 on port 1234 on two different IP addresses:
13439 local_interfaces = <; 192.168.23.65.1234 ; \
13440 3ffe:ffff:836f::fe86:a061.1234
13443 The IP address is enclosed in square brackets, and the port is added
13444 with a colon separator, for example:
13446 local_interfaces = <; [192.168.23.65]:1234 ; \
13447 [3ffe:ffff:836f::fe86:a061]:1234
13451 When a port is not specified, the value of &%daemon_smtp_ports%& is used. The
13452 default setting contains just one port:
13454 daemon_smtp_ports = smtp
13456 If more than one port is listed, each interface that does not have its own port
13457 specified listens on all of them. Ports that are listed in
13458 &%daemon_smtp_ports%& can be identified either by name (defined in
13459 &_/etc/services_&) or by number. However, when ports are given with individual
13460 IP addresses in &%local_interfaces%&, only numbers (not names) can be used.
13464 .section "Special IP listening addresses" "SECID90"
13465 The addresses 0.0.0.0 and ::0 are treated specially. They are interpreted
13466 as &"all IPv4 interfaces"& and &"all IPv6 interfaces"&, respectively. In each
13467 case, Exim tells the TCP/IP stack to &"listen on all IPv&'x'& interfaces"&
13468 instead of setting up separate listening sockets for each interface. The
13469 default value of &%local_interfaces%& is
13471 local_interfaces = 0.0.0.0
13473 when Exim is built without IPv6 support; otherwise it is:
13475 local_interfaces = <; ::0 ; 0.0.0.0
13477 Thus, by default, Exim listens on all available interfaces, on the SMTP port.
13481 .section "Overriding local_interfaces and daemon_smtp_ports" "SECID91"
13482 The &%-oX%& command line option can be used to override the values of
13483 &%daemon_smtp_ports%& and/or &%local_interfaces%& for a particular daemon
13484 instance. Another way of doing this would be to use macros and the &%-D%&
13485 option. However, &%-oX%& can be used by any admin user, whereas modification of
13486 the runtime configuration by &%-D%& is allowed only when the caller is root or
13489 The value of &%-oX%& is a list of items. The default colon separator can be
13490 changed in the usual way if required. If there are any items that do not
13491 contain dots or colons (that is, are not IP addresses), the value of
13492 &%daemon_smtp_ports%& is replaced by the list of those items. If there are any
13493 items that do contain dots or colons, the value of &%local_interfaces%& is
13494 replaced by those items. Thus, for example,
13498 overrides &%daemon_smtp_ports%&, but leaves &%local_interfaces%& unchanged,
13501 -oX 192.168.34.5.1125
13503 overrides &%local_interfaces%&, leaving &%daemon_smtp_ports%& unchanged.
13504 (However, since &%local_interfaces%& now contains no items without ports, the
13505 value of &%daemon_smtp_ports%& is no longer relevant in this example.)
13509 .section "Support for the submissions (aka SSMTP or SMTPS) protocol" "SECTsupobssmt"
13510 .cindex "submissions protocol"
13511 .cindex "ssmtp protocol"
13512 .cindex "smtps protocol"
13513 .cindex "SMTP" "ssmtp protocol"
13514 .cindex "SMTP" "smtps protocol"
13515 Exim supports the use of TLS-on-connect, used by mail clients in the
13516 &"submissions"& protocol, historically also known as SMTPS or SSMTP.
13517 For some years, IETF Standards Track documents only blessed the
13518 STARTTLS-based Submission service (port 587) while common practice was to support
13519 the same feature set on port 465, but using TLS-on-connect.
13520 If your installation needs to provide service to mail clients
13521 (Mail User Agents, MUAs) then you should provide service on both the 587 and
13524 If the &%tls_on_connect_ports%& option is set to a list of port numbers or
13525 service names, connections to those ports must first establish TLS, before
13526 proceeding to the application layer use of the SMTP protocol.
13528 The common use of this option is expected to be
13530 tls_on_connect_ports = 465
13533 There is also a command line option &%-tls-on-connect%&, which forces all ports
13534 to behave in this way when a daemon is started.
13536 &*Warning*&: Setting &%tls_on_connect_ports%& does not of itself cause the
13537 daemon to listen on those ports. You must still specify them in
13538 &%daemon_smtp_ports%&, &%local_interfaces%&, or the &%-oX%& option. (This is
13539 because &%tls_on_connect_ports%& applies to &%inetd%& connections as well as to
13540 connections via the daemon.)
13545 .section "IPv6 address scopes" "SECID92"
13546 .cindex "IPv6" "address scopes"
13547 IPv6 addresses have &"scopes"&, and a host with multiple hardware interfaces
13548 can, in principle, have the same link-local IPv6 address on different
13549 interfaces. Thus, additional information is needed, over and above the IP
13550 address, to distinguish individual interfaces. A convention of using a
13551 percent sign followed by something (often the interface name) has been
13552 adopted in some cases, leading to addresses like this:
13554 fe80::202:b3ff:fe03:45c1%eth0
13556 To accommodate this usage, a percent sign followed by an arbitrary string is
13557 allowed at the end of an IPv6 address. By default, Exim calls &[getaddrinfo()]&
13558 to convert a textual IPv6 address for actual use. This function recognizes the
13559 percent convention in operating systems that support it, and it processes the
13560 address appropriately. Unfortunately, some older libraries have problems with
13561 &[getaddrinfo()]&. If
13563 IPV6_USE_INET_PTON=yes
13565 is set in &_Local/Makefile_& (or an OS-dependent Makefile) when Exim is built,
13566 Exim uses &'inet_pton()'& to convert a textual IPv6 address for actual use,
13567 instead of &[getaddrinfo()]&. (Before version 4.14, it always used this
13568 function.) Of course, this means that the additional functionality of
13569 &[getaddrinfo()]& &-- recognizing scoped addresses &-- is lost.
13571 .section "Disabling IPv6" "SECID93"
13572 .cindex "IPv6" "disabling"
13573 Sometimes it happens that an Exim binary that was compiled with IPv6 support is
13574 run on a host whose kernel does not support IPv6. The binary will fall back to
13575 using IPv4, but it may waste resources looking up AAAA records, and trying to
13576 connect to IPv6 addresses, causing delays to mail delivery. If you set the
13577 .oindex "&%disable_ipv6%&"
13578 &%disable_ipv6%& option true, even if the Exim binary has IPv6 support, no IPv6
13579 activities take place. AAAA records are never looked up, and any IPv6 addresses
13580 that are listed in &%local_interfaces%&, data for the &(manualroute)& router,
13581 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
13582 to handle IPv6 literal addresses.
13584 On the other hand, when IPv6 is in use, there may be times when you want to
13585 disable it for certain hosts or domains. You can use the &%dns_ipv4_lookup%&
13586 option to globally suppress the lookup of AAAA records for specified domains,
13587 and you can use the &%ignore_target_hosts%& generic router option to ignore
13588 IPv6 addresses in an individual router.
13592 .section "Examples of starting a listening daemon" "SECID94"
13593 The default case in an IPv6 environment is
13595 daemon_smtp_ports = smtp
13596 local_interfaces = <; ::0 ; 0.0.0.0
13598 This specifies listening on the smtp port on all IPv6 and IPv4 interfaces.
13599 Either one or two sockets may be used, depending on the characteristics of
13600 the TCP/IP stack. (This is complicated and messy; for more information,
13601 read the comments in the &_daemon.c_& source file.)
13603 To specify listening on ports 25 and 26 on all interfaces:
13605 daemon_smtp_ports = 25 : 26
13607 (leaving &%local_interfaces%& at the default setting) or, more explicitly:
13609 local_interfaces = <; ::0.25 ; ::0.26 \
13610 0.0.0.0.25 ; 0.0.0.0.26
13612 To listen on the default port on all IPv4 interfaces, and on port 26 on the
13613 IPv4 loopback address only:
13615 local_interfaces = 0.0.0.0 : 127.0.0.1.26
13617 To specify listening on the default port on specific interfaces only:
13619 local_interfaces = 10.0.0.67 : 192.168.34.67
13621 &*Warning*&: Such a setting excludes listening on the loopback interfaces.
13625 .section "Recognizing the local host" "SECTreclocipadd"
13626 The &%local_interfaces%& option is also used when Exim needs to determine
13627 whether or not an IP address refers to the local host. That is, the IP
13628 addresses of all the interfaces on which a daemon is listening are always
13631 For this usage, port numbers in &%local_interfaces%& are ignored. If either of
13632 the items 0.0.0.0 or ::0 are encountered, Exim gets a complete list of
13633 available interfaces from the operating system, and extracts the relevant
13634 (that is, IPv4 or IPv6) addresses to use for checking.
13636 Some systems set up large numbers of virtual interfaces in order to provide
13637 many virtual web servers. In this situation, you may want to listen for
13638 email on only a few of the available interfaces, but nevertheless treat all
13639 interfaces as local when routing. You can do this by setting
13640 &%extra_local_interfaces%& to a list of IP addresses, possibly including the
13641 &"all"& wildcard values. These addresses are recognized as local, but are not
13642 used for listening. Consider this example:
13644 local_interfaces = <; 127.0.0.1 ; ::1 ; \
13646 3ffe:2101:12:1:a00:20ff:fe86:a061
13648 extra_local_interfaces = <; ::0 ; 0.0.0.0
13650 The daemon listens on the loopback interfaces and just one IPv4 and one IPv6
13651 address, but all available interface addresses are treated as local when
13654 In some environments the local host name may be in an MX list, but with an IP
13655 address that is not assigned to any local interface. In other cases it may be
13656 desirable to treat other host names as if they referred to the local host. Both
13657 these cases can be handled by setting the &%hosts_treat_as_local%& option.
13658 This contains host names rather than IP addresses. When a host is referenced
13659 during routing, either via an MX record or directly, it is treated as the local
13660 host if its name matches &%hosts_treat_as_local%&, or if any of its IP
13661 addresses match &%local_interfaces%& or &%extra_local_interfaces%&.
13665 .section "Delivering to a remote host" "SECID95"
13666 Delivery to a remote host is handled by the smtp transport. By default, it
13667 allows the system's TCP/IP functions to choose which interface to use (if
13668 there is more than one) when connecting to a remote host. However, the
13669 &%interface%& option can be set to specify which interface is used. See the
13670 description of the smtp transport in chapter &<<CHAPsmtptrans>>& for more
13676 . ////////////////////////////////////////////////////////////////////////////
13677 . ////////////////////////////////////////////////////////////////////////////
13679 .chapter "Main configuration" "CHAPmainconfig"
13680 .scindex IIDconfima "configuration file" "main section"
13681 .scindex IIDmaiconf "main configuration"
13682 The first part of the run time configuration file contains three types of item:
13685 Macro definitions: These lines start with an upper case letter. See section
13686 &<<SECTmacrodefs>>& for details of macro processing.
13688 Named list definitions: These lines start with one of the words &"domainlist"&,
13689 &"hostlist"&, &"addresslist"&, or &"localpartlist"&. Their use is described in
13690 section &<<SECTnamedlists>>&.
13692 Main configuration settings: Each setting occupies one line of the file
13693 (with possible continuations). If any setting is preceded by the word
13694 &"hide"&, the &%-bP%& command line option displays its value to admin users
13695 only. See section &<<SECTcos>>& for a description of the syntax of these option
13699 This chapter specifies all the main configuration options, along with their
13700 types and default values. For ease of finding a particular option, they appear
13701 in alphabetical order in section &<<SECTalomo>>& below. However, because there
13702 are now so many options, they are first listed briefly in functional groups, as
13703 an aid to finding the name of the option you are looking for. Some options are
13704 listed in more than one group.
13706 .section "Miscellaneous" "SECID96"
13708 .row &%bi_command%& "to run for &%-bi%& command line option"
13709 .row &%debug_store%& "do extra internal checks"
13710 .row &%disable_ipv6%& "do no IPv6 processing"
13711 .row &%keep_malformed%& "for broken files &-- should not happen"
13712 .row &%localhost_number%& "for unique message ids in clusters"
13713 .row &%message_body_newlines%& "retain newlines in &$message_body$&"
13714 .row &%message_body_visible%& "how much to show in &$message_body$&"
13715 .row &%mua_wrapper%& "run in &""MUA wrapper""& mode"
13716 .row &%print_topbitchars%& "top-bit characters are printing"
13717 .row &%spool_wireformat%& "use wire-format spool data files when possible"
13718 .row &%timezone%& "force time zone"
13722 .section "Exim parameters" "SECID97"
13724 .row &%exim_group%& "override compiled-in value"
13725 .row &%exim_path%& "override compiled-in value"
13726 .row &%exim_user%& "override compiled-in value"
13727 .row &%primary_hostname%& "default from &[uname()]&"
13728 .row &%split_spool_directory%& "use multiple directories"
13729 .row &%spool_directory%& "override compiled-in value"
13734 .section "Privilege controls" "SECID98"
13736 .row &%admin_groups%& "groups that are Exim admin users"
13737 .row &%commandline_checks_require_admin%& "require admin for various checks"
13738 .row &%deliver_drop_privilege%& "drop root for delivery processes"
13739 .row &%local_from_check%& "insert &'Sender:'& if necessary"
13740 .row &%local_from_prefix%& "for testing &'From:'& for local sender"
13741 .row &%local_from_suffix%& "for testing &'From:'& for local sender"
13742 .row &%local_sender_retain%& "keep &'Sender:'& from untrusted user"
13743 .row &%never_users%& "do not run deliveries as these"
13744 .row &%prod_requires_admin%& "forced delivery requires admin user"
13745 .row &%queue_list_requires_admin%& "queue listing requires admin user"
13746 .row &%trusted_groups%& "groups that are trusted"
13747 .row &%trusted_users%& "users that are trusted"
13752 .section "Logging" "SECID99"
13754 .row &%event_action%& "custom logging"
13755 .row &%hosts_connection_nolog%& "exemption from connect logging"
13756 .row &%log_file_path%& "override compiled-in value"
13757 .row &%log_selector%& "set/unset optional logging"
13758 .row &%log_timezone%& "add timezone to log lines"
13759 .row &%message_logs%& "create per-message logs"
13760 .row &%preserve_message_logs%& "after message completion"
13761 .row &%process_log_path%& "for SIGUSR1 and &'exiwhat'&"
13762 .row &%slow_lookup_log%& "control logging of slow DNS lookups"
13763 .row &%syslog_duplication%& "controls duplicate log lines on syslog"
13764 .row &%syslog_facility%& "set syslog &""facility""& field"
13765 .row &%syslog_pid%& "pid in syslog lines"
13766 .row &%syslog_processname%& "set syslog &""ident""& field"
13767 .row &%syslog_timestamp%& "timestamp syslog lines"
13768 .row &%write_rejectlog%& "control use of message log"
13773 .section "Frozen messages" "SECID100"
13775 .row &%auto_thaw%& "sets time for retrying frozen messages"
13776 .row &%freeze_tell%& "send message when freezing"
13777 .row &%move_frozen_messages%& "to another directory"
13778 .row &%timeout_frozen_after%& "keep frozen messages only so long"
13783 .section "Data lookups" "SECID101"
13785 .row &%ibase_servers%& "InterBase servers"
13786 .row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's"
13787 .row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's"
13788 .row &%ldap_cert_file%& "client cert file for LDAP"
13789 .row &%ldap_cert_key%& "client key file for LDAP"
13790 .row &%ldap_cipher_suite%& "TLS negotiation preference control"
13791 .row &%ldap_default_servers%& "used if no server in query"
13792 .row &%ldap_require_cert%& "action to take without LDAP server cert"
13793 .row &%ldap_start_tls%& "require TLS within LDAP"
13794 .row &%ldap_version%& "set protocol version"
13795 .row &%lookup_open_max%& "lookup files held open"
13796 .row &%mysql_servers%& "default MySQL servers"
13797 .row &%oracle_servers%& "Oracle servers"
13798 .row &%pgsql_servers%& "default PostgreSQL servers"
13799 .row &%sqlite_lock_timeout%& "as it says"
13804 .section "Message ids" "SECID102"
13806 .row &%message_id_header_domain%& "used to build &'Message-ID:'& header"
13807 .row &%message_id_header_text%& "ditto"
13812 .section "Embedded Perl Startup" "SECID103"
13814 .row &%perl_at_start%& "always start the interpreter"
13815 .row &%perl_startup%& "code to obey when starting Perl"
13816 .row &%perl_taintmode%& "enable taint mode in Perl"
13821 .section "Daemon" "SECID104"
13823 .row &%daemon_smtp_ports%& "default ports"
13824 .row &%daemon_startup_retries%& "number of times to retry"
13825 .row &%daemon_startup_sleep%& "time to sleep between tries"
13826 .row &%extra_local_interfaces%& "not necessarily listened on"
13827 .row &%local_interfaces%& "on which to listen, with optional ports"
13828 .row &%pid_file_path%& "override compiled-in value"
13829 .row &%queue_run_max%& "maximum simultaneous queue runners"
13834 .section "Resource control" "SECID105"
13836 .row &%check_log_inodes%& "before accepting a message"
13837 .row &%check_log_space%& "before accepting a message"
13838 .row &%check_spool_inodes%& "before accepting a message"
13839 .row &%check_spool_space%& "before accepting a message"
13840 .row &%deliver_queue_load_max%& "no queue deliveries if load high"
13841 .row &%queue_only_load%& "queue incoming if load high"
13842 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
13843 .row &%queue_run_max%& "maximum simultaneous queue runners"
13844 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
13845 .row &%smtp_accept_max%& "simultaneous incoming connections"
13846 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13847 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
13848 .row &%smtp_accept_max_per_connection%& "messages per connection"
13849 .row &%smtp_accept_max_per_host%& "connections from one host"
13850 .row &%smtp_accept_queue%& "queue mail if more connections"
13851 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
13853 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
13854 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
13855 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
13856 .row &%smtp_load_reserve%& "SMTP from reserved hosts if load high"
13857 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
13862 .section "Policy controls" "SECID106"
13864 .row &%acl_not_smtp%& "ACL for non-SMTP messages"
13865 .row &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
13866 .row &%acl_not_smtp_start%& "ACL for start of non-SMTP message"
13867 .row &%acl_smtp_auth%& "ACL for AUTH"
13868 .row &%acl_smtp_connect%& "ACL for connection"
13869 .row &%acl_smtp_data%& "ACL for DATA"
13870 .row &%acl_smtp_data_prdr%& "ACL for DATA, per-recipient"
13871 .row &%acl_smtp_dkim%& "ACL for DKIM verification"
13872 .row &%acl_smtp_etrn%& "ACL for ETRN"
13873 .row &%acl_smtp_expn%& "ACL for EXPN"
13874 .row &%acl_smtp_helo%& "ACL for EHLO or HELO"
13875 .row &%acl_smtp_mail%& "ACL for MAIL"
13876 .row &%acl_smtp_mailauth%& "ACL for AUTH on MAIL command"
13877 .row &%acl_smtp_mime%& "ACL for MIME parts"
13878 .row &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
13879 .row &%acl_smtp_predata%& "ACL for start of data"
13880 .row &%acl_smtp_quit%& "ACL for QUIT"
13881 .row &%acl_smtp_rcpt%& "ACL for RCPT"
13882 .row &%acl_smtp_starttls%& "ACL for STARTTLS"
13883 .row &%acl_smtp_vrfy%& "ACL for VRFY"
13884 .row &%av_scanner%& "specify virus scanner"
13885 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
13887 .row &%dns_cname_loops%& "follow CNAMEs returned by resolver"
13888 .row &%dns_csa_search_limit%& "control CSA parent search depth"
13889 .row &%dns_csa_use_reverse%& "en/disable CSA IP reverse search"
13890 .row &%header_maxsize%& "total size of message header"
13891 .row &%header_line_maxsize%& "individual header line limit"
13892 .row &%helo_accept_junk_hosts%& "allow syntactic junk from these hosts"
13893 .row &%helo_allow_chars%& "allow illegal chars in HELO names"
13894 .row &%helo_lookup_domains%& "lookup hostname for these HELO names"
13895 .row &%helo_try_verify_hosts%& "HELO soft-checked for these hosts"
13896 .row &%helo_verify_hosts%& "HELO hard-checked for these hosts"
13897 .row &%host_lookup%& "host name looked up for these hosts"
13898 .row &%host_lookup_order%& "order of DNS and local name lookups"
13899 .row &%hosts_proxy%& "use proxy protocol for these hosts"
13900 .row &%host_reject_connection%& "reject connection from these hosts"
13901 .row &%hosts_treat_as_local%& "useful in some cluster configurations"
13902 .row &%local_scan_timeout%& "timeout for &[local_scan()]&"
13903 .row &%message_size_limit%& "for all messages"
13904 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13905 .row &%spamd_address%& "set interface to SpamAssassin"
13906 .row &%strict_acl_vars%& "object to unset ACL variables"
13911 .section "Callout cache" "SECID107"
13913 .row &%callout_domain_negative_expire%& "timeout for negative domain cache &&&
13915 .row &%callout_domain_positive_expire%& "timeout for positive domain cache &&&
13917 .row &%callout_negative_expire%& "timeout for negative address cache item"
13918 .row &%callout_positive_expire%& "timeout for positive address cache item"
13919 .row &%callout_random_local_part%& "string to use for &""random""& testing"
13924 .section "TLS" "SECID108"
13926 .row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
13927 .row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
13928 .row &%openssl_options%& "adjust OpenSSL compatibility options"
13929 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
13930 .row &%tls_certificate%& "location of server certificate"
13931 .row &%tls_crl%& "certificate revocation list"
13932 .row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
13933 .row &%tls_dhparam%& "DH parameters for server"
13934 .row &%tls_eccurve%& "EC curve selection for server"
13935 .row &%tls_ocsp_file%& "location of server certificate status proof"
13936 .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports"
13937 .row &%tls_privatekey%& "location of server private key"
13938 .row &%tls_remember_esmtp%& "don't reset after starting TLS"
13939 .row &%tls_require_ciphers%& "specify acceptable ciphers"
13940 .row &%tls_try_verify_hosts%& "try to verify client certificate"
13941 .row &%tls_verify_certificates%& "expected client certificates"
13942 .row &%tls_verify_hosts%& "insist on client certificate verify"
13947 .section "Local user handling" "SECID109"
13949 .row &%finduser_retries%& "useful in NIS environments"
13950 .row &%gecos_name%& "used when creating &'Sender:'&"
13951 .row &%gecos_pattern%& "ditto"
13952 .row &%max_username_length%& "for systems that truncate"
13953 .row &%unknown_login%& "used when no login name found"
13954 .row &%unknown_username%& "ditto"
13955 .row &%uucp_from_pattern%& "for recognizing &""From ""& lines"
13956 .row &%uucp_from_sender%& "ditto"
13961 .section "All incoming messages (SMTP and non-SMTP)" "SECID110"
13963 .row &%header_maxsize%& "total size of message header"
13964 .row &%header_line_maxsize%& "individual header line limit"
13965 .row &%message_size_limit%& "applies to all messages"
13966 .row &%percent_hack_domains%& "recognize %-hack for these domains"
13967 .row &%received_header_text%& "expanded to make &'Received:'&"
13968 .row &%received_headers_max%& "for mail loop detection"
13969 .row &%recipients_max%& "limit per message"
13970 .row &%recipients_max_reject%& "permanently reject excess recipients"
13976 .section "Non-SMTP incoming messages" "SECID111"
13978 .row &%receive_timeout%& "for non-SMTP messages"
13985 .section "Incoming SMTP messages" "SECID112"
13986 See also the &'Policy controls'& section above.
13989 .row &%dkim_verify_signers%& "DKIM domain for which DKIM ACL is run"
13990 .row &%host_lookup%& "host name looked up for these hosts"
13991 .row &%host_lookup_order%& "order of DNS and local name lookups"
13992 .row &%recipient_unqualified_hosts%& "may send unqualified recipients"
13993 .row &%rfc1413_hosts%& "make ident calls to these hosts"
13994 .row &%rfc1413_query_timeout%& "zero disables ident calls"
13995 .row &%sender_unqualified_hosts%& "may send unqualified senders"
13996 .row &%smtp_accept_keepalive%& "some TCP/IP magic"
13997 .row &%smtp_accept_max%& "simultaneous incoming connections"
13998 .row &%smtp_accept_max_nonmail%& "non-mail commands"
13999 .row &%smtp_accept_max_nonmail_hosts%& "hosts to which the limit applies"
14000 .row &%smtp_accept_max_per_connection%& "messages per connection"
14001 .row &%smtp_accept_max_per_host%& "connections from one host"
14002 .row &%smtp_accept_queue%& "queue mail if more connections"
14003 .row &%smtp_accept_queue_per_connection%& "queue if more messages per &&&
14005 .row &%smtp_accept_reserve%& "only reserve hosts if more connections"
14006 .row &%smtp_active_hostname%& "host name to use in messages"
14007 .row &%smtp_banner%& "text for welcome banner"
14008 .row &%smtp_check_spool_space%& "from SIZE on MAIL command"
14009 .row &%smtp_connect_backlog%& "passed to TCP/IP stack"
14010 .row &%smtp_enforce_sync%& "of SMTP command/responses"
14011 .row &%smtp_etrn_command%& "what to run for ETRN"
14012 .row &%smtp_etrn_serialize%& "only one at once"
14013 .row &%smtp_load_reserve%& "only reserve hosts if this load"
14014 .row &%smtp_max_unknown_commands%& "before dropping connection"
14015 .row &%smtp_ratelimit_hosts%& "apply ratelimiting to these hosts"
14016 .row &%smtp_ratelimit_mail%& "ratelimit for MAIL commands"
14017 .row &%smtp_ratelimit_rcpt%& "ratelimit for RCPT commands"
14018 .row &%smtp_receive_timeout%& "per command or data line"
14019 .row &%smtp_reserve_hosts%& "these are the reserve hosts"
14020 .row &%smtp_return_error_details%& "give detail on rejections"
14025 .section "SMTP extensions" "SECID113"
14027 .row &%accept_8bitmime%& "advertise 8BITMIME"
14028 .row &%auth_advertise_hosts%& "advertise AUTH to these hosts"
14029 .row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts"
14030 .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts"
14031 .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts"
14032 .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP"
14033 .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts"
14034 .row &%prdr_enable%& "advertise PRDR to all hosts"
14035 .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts"
14036 .row &%tls_advertise_hosts%& "advertise TLS to these hosts"
14041 .section "Processing messages" "SECID114"
14043 .row &%allow_domain_literals%& "recognize domain literal syntax"
14044 .row &%allow_mx_to_ip%& "allow MX to point to IP address"
14045 .row &%allow_utf8_domains%& "in addresses"
14046 .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&&
14048 .row &%delivery_date_remove%& "from incoming messages"
14049 .row &%envelope_to_remove%& "from incoming messages"
14050 .row &%extract_addresses_remove_arguments%& "affects &%-t%& processing"
14051 .row &%headers_charset%& "default for translations"
14052 .row &%qualify_domain%& "default for senders"
14053 .row &%qualify_recipient%& "default for recipients"
14054 .row &%return_path_remove%& "from incoming messages"
14055 .row &%strip_excess_angle_brackets%& "in addresses"
14056 .row &%strip_trailing_dot%& "at end of addresses"
14057 .row &%untrusted_set_sender%& "untrusted can set envelope sender"
14062 .section "System filter" "SECID115"
14064 .row &%system_filter%& "locate system filter"
14065 .row &%system_filter_directory_transport%& "transport for delivery to a &&&
14067 .row &%system_filter_file_transport%& "transport for delivery to a file"
14068 .row &%system_filter_group%& "group for filter running"
14069 .row &%system_filter_pipe_transport%& "transport for delivery to a pipe"
14070 .row &%system_filter_reply_transport%& "transport for autoreply delivery"
14071 .row &%system_filter_user%& "user for filter running"
14076 .section "Routing and delivery" "SECID116"
14078 .row &%disable_ipv6%& "do no IPv6 processing"
14079 .row &%dns_again_means_nonexist%& "for broken domains"
14080 .row &%dns_check_names_pattern%& "pre-DNS syntax check"
14081 .row &%dns_dnssec_ok%& "parameter for resolver"
14082 .row &%dns_ipv4_lookup%& "only v4 lookup for these domains"
14083 .row &%dns_retrans%& "parameter for resolver"
14084 .row &%dns_retry%& "parameter for resolver"
14085 .row &%dns_trust_aa%& "DNS zones trusted as authentic"
14086 .row &%dns_use_edns0%& "parameter for resolver"
14087 .row &%hold_domains%& "hold delivery for these domains"
14088 .row &%local_interfaces%& "for routing checks"
14089 .row &%queue_domains%& "no immediate delivery for these"
14090 .row &%queue_only%& "no immediate delivery at all"
14091 .row &%queue_only_file%& "no immediate delivery if file exists"
14092 .row &%queue_only_load%& "no immediate delivery if load is high"
14093 .row &%queue_only_load_latch%& "don't re-evaluate load for each message"
14094 .row &%queue_only_override%& "allow command line to override"
14095 .row &%queue_run_in_order%& "order of arrival"
14096 .row &%queue_run_max%& "of simultaneous queue runners"
14097 .row &%queue_smtp_domains%& "no immediate SMTP delivery for these"
14098 .row &%remote_max_parallel%& "parallel SMTP delivery per message"
14099 .row &%remote_sort_domains%& "order of remote deliveries"
14100 .row &%retry_data_expire%& "timeout for retry data"
14101 .row &%retry_interval_max%& "safety net for retry rules"
14106 .section "Bounce and warning messages" "SECID117"
14108 .row &%bounce_message_file%& "content of bounce"
14109 .row &%bounce_message_text%& "content of bounce"
14110 .row &%bounce_return_body%& "include body if returning message"
14111 .row &%bounce_return_linesize_limit%& "limit on returned message line length"
14112 .row &%bounce_return_message%& "include original message in bounce"
14113 .row &%bounce_return_size_limit%& "limit on returned message"
14114 .row &%bounce_sender_authentication%& "send authenticated sender with bounce"
14115 .row &%dsn_from%& "set &'From:'& contents in bounces"
14116 .row &%errors_copy%& "copy bounce messages"
14117 .row &%errors_reply_to%& "&'Reply-to:'& in bounces"
14118 .row &%delay_warning%& "time schedule"
14119 .row &%delay_warning_condition%& "condition for warning messages"
14120 .row &%ignore_bounce_errors_after%& "discard undeliverable bounces"
14121 .row &%smtp_return_error_details%& "give detail on rejections"
14122 .row &%warn_message_file%& "content of warning message"
14127 .section "Alphabetical list of main options" "SECTalomo"
14128 Those options that undergo string expansion before use are marked with
14131 .option accept_8bitmime main boolean true
14133 .cindex "8-bit characters"
14134 .cindex "log" "selectors"
14135 .cindex "log" "8BITMIME"
14136 This option causes Exim to send 8BITMIME in its response to an SMTP
14137 EHLO command, and to accept the BODY= parameter on MAIL commands.
14138 However, though Exim is 8-bit clean, it is not a protocol converter, and it
14139 takes no steps to do anything special with messages received by this route.
14141 Historically Exim kept this option off by default, but the maintainers
14142 feel that in today's Internet, this causes more problems than it solves.
14143 It now defaults to true.
14144 A more detailed analysis of the issues is provided by Dan Bernstein:
14146 &url(http://cr.yp.to/smtp/8bitmime.html)
14149 To log received 8BITMIME status use
14151 log_selector = +8bitmime
14154 .option acl_not_smtp main string&!! unset
14155 .cindex "&ACL;" "for non-SMTP messages"
14156 .cindex "non-SMTP messages" "ACLs for"
14157 This option defines the ACL that is run when a non-SMTP message has been
14158 read and is on the point of being accepted. See chapter &<<CHAPACL>>& for
14161 .option acl_not_smtp_mime main string&!! unset
14162 This option defines the ACL that is run for individual MIME parts of non-SMTP
14163 messages. It operates in exactly the same way as &%acl_smtp_mime%& operates for
14166 .option acl_not_smtp_start main string&!! unset
14167 .cindex "&ACL;" "at start of non-SMTP message"
14168 .cindex "non-SMTP messages" "ACLs for"
14169 This option defines the ACL that is run before Exim starts reading a
14170 non-SMTP message. See chapter &<<CHAPACL>>& for further details.
14172 .option acl_smtp_auth main string&!! unset
14173 .cindex "&ACL;" "setting up for SMTP commands"
14174 .cindex "AUTH" "ACL for"
14175 This option defines the ACL that is run when an SMTP AUTH command is
14176 received. See chapter &<<CHAPACL>>& for further details.
14178 .option acl_smtp_connect main string&!! unset
14179 .cindex "&ACL;" "on SMTP connection"
14180 This option defines the ACL that is run when an SMTP connection is received.
14181 See chapter &<<CHAPACL>>& for further details.
14183 .option acl_smtp_data main string&!! unset
14184 .cindex "DATA" "ACL for"
14185 This option defines the ACL that is run after an SMTP DATA command has been
14186 processed and the message itself has been received, but before the final
14187 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14189 .option acl_smtp_data_prdr main string&!! accept
14190 .cindex "PRDR" "ACL for"
14191 .cindex "DATA" "PRDR ACL for"
14192 .cindex "&ACL;" "PRDR-related"
14193 .cindex "&ACL;" "per-user data processing"
14194 This option defines the ACL that,
14195 if the PRDR feature has been negotiated,
14196 is run for each recipient after an SMTP DATA command has been
14197 processed and the message itself has been received, but before the
14198 acknowledgment is sent. See chapter &<<CHAPACL>>& for further details.
14200 .option acl_smtp_dkim main string&!! unset
14201 .cindex DKIM "ACL for"
14202 This option defines the ACL that is run for each DKIM signature
14203 (by default, or as specified in the dkim_verify_signers option)
14204 of a received message.
14205 See section &<<SECDKIMVFY>>& for further details.
14207 .option acl_smtp_etrn main string&!! unset
14208 .cindex "ETRN" "ACL for"
14209 This option defines the ACL that is run when an SMTP ETRN command is
14210 received. See chapter &<<CHAPACL>>& for further details.
14212 .option acl_smtp_expn main string&!! unset
14213 .cindex "EXPN" "ACL for"
14214 This option defines the ACL that is run when an SMTP EXPN command is
14215 received. See chapter &<<CHAPACL>>& for further details.
14217 .option acl_smtp_helo main string&!! unset
14218 .cindex "EHLO" "ACL for"
14219 .cindex "HELO" "ACL for"
14220 This option defines the ACL that is run when an SMTP EHLO or HELO
14221 command is received. See chapter &<<CHAPACL>>& for further details.
14224 .option acl_smtp_mail main string&!! unset
14225 .cindex "MAIL" "ACL for"
14226 This option defines the ACL that is run when an SMTP MAIL command is
14227 received. See chapter &<<CHAPACL>>& for further details.
14229 .option acl_smtp_mailauth main string&!! unset
14230 .cindex "AUTH" "on MAIL command"
14231 This option defines the ACL that is run when there is an AUTH parameter on
14232 a MAIL command. See chapter &<<CHAPACL>>& for details of ACLs, and chapter
14233 &<<CHAPSMTPAUTH>>& for details of authentication.
14235 .option acl_smtp_mime main string&!! unset
14236 .cindex "MIME content scanning" "ACL for"
14237 This option is available when Exim is built with the content-scanning
14238 extension. It defines the ACL that is run for each MIME part in a message. See
14239 section &<<SECTscanmimepart>>& for details.
14241 .option acl_smtp_notquit main string&!! unset
14242 .cindex "not-QUIT, ACL for"
14243 This option defines the ACL that is run when an SMTP session
14244 ends without a QUIT command being received.
14245 See chapter &<<CHAPACL>>& for further details.
14247 .option acl_smtp_predata main string&!! unset
14248 This option defines the ACL that is run when an SMTP DATA command is
14249 received, before the message itself is received. See chapter &<<CHAPACL>>& for
14252 .option acl_smtp_quit main string&!! unset
14253 .cindex "QUIT, ACL for"
14254 This option defines the ACL that is run when an SMTP QUIT command is
14255 received. See chapter &<<CHAPACL>>& for further details.
14257 .option acl_smtp_rcpt main string&!! unset
14258 .cindex "RCPT" "ACL for"
14259 This option defines the ACL that is run when an SMTP RCPT command is
14260 received. See chapter &<<CHAPACL>>& for further details.
14262 .option acl_smtp_starttls main string&!! unset
14263 .cindex "STARTTLS, ACL for"
14264 This option defines the ACL that is run when an SMTP STARTTLS command is
14265 received. See chapter &<<CHAPACL>>& for further details.
14267 .option acl_smtp_vrfy main string&!! unset
14268 .cindex "VRFY" "ACL for"
14269 This option defines the ACL that is run when an SMTP VRFY command is
14270 received. See chapter &<<CHAPACL>>& for further details.
14272 .option add_environment main "string list" empty
14273 .cindex "environment" "set values"
14274 This option allows to set individual environment variables that the
14275 currently linked libraries and programs in child processes use.
14276 See &<<SECTpipeenv>>& for the environment of &(pipe)& transports.
14278 .option admin_groups main "string list&!!" unset
14279 .cindex "admin user"
14280 This option is expanded just once, at the start of Exim's processing. If the
14281 current group or any of the supplementary groups of an Exim caller is in this
14282 colon-separated list, the caller has admin privileges. If all your system
14283 programmers are in a specific group, for example, you can give them all Exim
14284 admin privileges by putting that group in &%admin_groups%&. However, this does
14285 not permit them to read Exim's spool files (whose group owner is the Exim gid).
14286 To permit this, you have to add individuals to the Exim group.
14288 .option allow_domain_literals main boolean false
14289 .cindex "domain literal"
14290 If this option is set, the RFC 2822 domain literal format is permitted in
14291 email addresses. The option is not set by default, because the domain literal
14292 format is not normally required these days, and few people know about it. It
14293 has, however, been exploited by mail abusers.
14295 Unfortunately, it seems that some DNS black list maintainers are using this
14296 format to report black listing to postmasters. If you want to accept messages
14297 addressed to your hosts by IP address, you need to set
14298 &%allow_domain_literals%& true, and also to add &`@[]`& to the list of local
14299 domains (defined in the named domain list &%local_domains%& in the default
14300 configuration). This &"magic string"& matches the domain literal form of all
14301 the local host's IP addresses.
14304 .option allow_mx_to_ip main boolean false
14305 .cindex "MX record" "pointing to IP address"
14306 It appears that more and more DNS zone administrators are breaking the rules
14307 and putting domain names that look like IP addresses on the right hand side of
14308 MX records. Exim follows the rules and rejects this, giving an error message
14309 that explains the misconfiguration. However, some other MTAs support this
14310 practice, so to avoid &"Why can't Exim do this?"& complaints,
14311 &%allow_mx_to_ip%& exists, in order to enable this heinous activity. It is not
14312 recommended, except when you have no other choice.
14314 .option allow_utf8_domains main boolean false
14315 .cindex "domain" "UTF-8 characters in"
14316 .cindex "UTF-8" "in domain name"
14317 Lots of discussion is going on about internationalized domain names. One
14318 camp is strongly in favour of just using UTF-8 characters, and it seems
14319 that at least two other MTAs permit this. This option allows Exim users to
14320 experiment if they wish.
14322 If it is set true, Exim's domain parsing function allows valid
14323 UTF-8 multicharacters to appear in domain name components, in addition to
14324 letters, digits, and hyphens. However, just setting this option is not
14325 enough; if you want to look up these domain names in the DNS, you must also
14326 adjust the value of &%dns_check_names_pattern%& to match the extended form. A
14327 suitable setting is:
14329 dns_check_names_pattern = (?i)^(?>(?(1)\.|())[a-z0-9\xc0-\xff]\
14330 (?>[-a-z0-9\x80-\xff]*[a-z0-9\x80-\xbf])?)+$
14332 Alternatively, you can just disable this feature by setting
14334 dns_check_names_pattern =
14336 That is, set the option to an empty string so that no check is done.
14339 .option auth_advertise_hosts main "host list&!!" *
14340 .cindex "authentication" "advertising"
14341 .cindex "AUTH" "advertising"
14342 If any server authentication mechanisms are configured, Exim advertises them in
14343 response to an EHLO command only if the calling host matches this list.
14344 Otherwise, Exim does not advertise AUTH.
14345 Exim does not accept AUTH commands from clients to which it has not
14346 advertised the availability of AUTH. The advertising of individual
14347 authentication mechanisms can be controlled by the use of the
14348 &%server_advertise_condition%& generic authenticator option on the individual
14349 authenticators. See chapter &<<CHAPSMTPAUTH>>& for further details.
14351 Certain mail clients (for example, Netscape) require the user to provide a name
14352 and password for authentication if AUTH is advertised, even though it may
14353 not be needed (the host may accept messages from hosts on its local LAN without
14354 authentication, for example). The &%auth_advertise_hosts%& option can be used
14355 to make these clients more friendly by excluding them from the set of hosts to
14356 which Exim advertises AUTH.
14358 .cindex "AUTH" "advertising when encrypted"
14359 If you want to advertise the availability of AUTH only when the connection
14360 is encrypted using TLS, you can make use of the fact that the value of this
14361 option is expanded, with a setting like this:
14363 auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}}
14365 .vindex "&$tls_in_cipher$&"
14366 If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of
14367 the expansion is empty, thus matching no hosts. Otherwise, the result of the
14368 expansion is *, which matches all hosts.
14371 .option auto_thaw main time 0s
14372 .cindex "thawing messages"
14373 .cindex "unfreezing messages"
14374 If this option is set to a time greater than zero, a queue runner will try a
14375 new delivery attempt on any frozen message, other than a bounce message, if
14376 this much time has passed since it was frozen. This may result in the message
14377 being re-frozen if nothing has changed since the last attempt. It is a way of
14378 saying &"keep on trying, even though there are big problems"&.
14380 &*Note*&: This is an old option, which predates &%timeout_frozen_after%& and
14381 &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not
14382 thought to be very useful any more, and its use should probably be avoided.
14385 .option av_scanner main string "see below"
14386 This option is available if Exim is built with the content-scanning extension.
14387 It specifies which anti-virus scanner to use. The default value is:
14389 sophie:/var/run/sophie
14391 If the value of &%av_scanner%& starts with a dollar character, it is expanded
14392 before use. See section &<<SECTscanvirus>>& for further details.
14395 .option bi_command main string unset
14397 This option supplies the name of a command that is run when Exim is called with
14398 the &%-bi%& option (see chapter &<<CHAPcommandline>>&). The string value is
14399 just the command name, it is not a complete command line. If an argument is
14400 required, it must come from the &%-oA%& command line option.
14403 .option bounce_message_file main string unset
14404 .cindex "bounce message" "customizing"
14405 .cindex "customizing" "bounce message"
14406 This option defines a template file containing paragraphs of text to be used
14407 for constructing bounce messages. Details of the file's contents are given in
14408 chapter &<<CHAPemsgcust>>&. See also &%warn_message_file%&.
14411 .option bounce_message_text main string unset
14412 When this option is set, its contents are included in the default bounce
14413 message immediately after &"This message was created automatically by mail
14414 delivery software."& It is not used if &%bounce_message_file%& is set.
14416 .option bounce_return_body main boolean true
14417 .cindex "bounce message" "including body"
14418 This option controls whether the body of an incoming message is included in a
14419 bounce message when &%bounce_return_message%& is true. The default setting
14420 causes the entire message, both header and body, to be returned (subject to the
14421 value of &%bounce_return_size_limit%&). If this option is false, only the
14422 message header is included. In the case of a non-SMTP message containing an
14423 error that is detected during reception, only those header lines preceding the
14424 point at which the error was detected are returned.
14425 .cindex "bounce message" "including original"
14427 .option bounce_return_linesize_limit main integer 998
14428 .cindex "size" "of bounce lines, limit"
14429 .cindex "bounce message" "line length limit"
14430 .cindex "limit" "bounce message line length"
14431 This option sets a limit in bytes on the line length of messages
14432 that are returned to senders due to delivery problems,
14433 when &%bounce_return_message%& is true.
14434 The default value corresponds to RFC limits.
14435 If the message being returned has lines longer than this value it is
14436 treated as if the &%bounce_return_size_limit%& (below) restriction was exceeded.
14438 The option also applies to bounces returned when an error is detected
14439 during reception of a message.
14440 In this case lines from the original are truncated.
14442 The option does not apply to messages generated by an &(autoreply)& transport.
14445 .option bounce_return_message main boolean true
14446 If this option is set false, none of the original message is included in
14447 bounce messages generated by Exim. See also &%bounce_return_size_limit%& and
14448 &%bounce_return_body%&.
14451 .option bounce_return_size_limit main integer 100K
14452 .cindex "size" "of bounce, limit"
14453 .cindex "bounce message" "size limit"
14454 .cindex "limit" "bounce message size"
14455 This option sets a limit in bytes on the size of messages that are returned to
14456 senders as part of bounce messages when &%bounce_return_message%& is true. The
14457 limit should be less than the value of the global &%message_size_limit%& and of
14458 any &%message_size_limit%& settings on transports, to allow for the bounce text
14459 that Exim generates. If this option is set to zero there is no limit.
14461 When the body of any message that is to be included in a bounce message is
14462 greater than the limit, it is truncated, and a comment pointing this out is
14463 added at the top. The actual cutoff may be greater than the value given, owing
14464 to the use of buffering for transferring the message in chunks (typically 8K in
14465 size). The idea is to save bandwidth on those undeliverable 15-megabyte
14468 .option bounce_sender_authentication main string unset
14469 .cindex "bounce message" "sender authentication"
14470 .cindex "authentication" "bounce message"
14471 .cindex "AUTH" "on bounce message"
14472 This option provides an authenticated sender address that is sent with any
14473 bounce messages generated by Exim that are sent over an authenticated SMTP
14474 connection. A typical setting might be:
14476 bounce_sender_authentication = mailer-daemon@my.domain.example
14478 which would cause bounce messages to be sent using the SMTP command:
14480 MAIL FROM:<> AUTH=mailer-daemon@my.domain.example
14482 The value of &%bounce_sender_authentication%& must always be a complete email
14485 .option callout_domain_negative_expire main time 3h
14486 .cindex "caching" "callout timeouts"
14487 .cindex "callout" "caching timeouts"
14488 This option specifies the expiry time for negative callout cache data for a
14489 domain. See section &<<SECTcallver>>& for details of callout verification, and
14490 section &<<SECTcallvercache>>& for details of the caching.
14493 .option callout_domain_positive_expire main time 7d
14494 This option specifies the expiry time for positive callout cache data for a
14495 domain. See section &<<SECTcallver>>& for details of callout verification, and
14496 section &<<SECTcallvercache>>& for details of the caching.
14499 .option callout_negative_expire main time 2h
14500 This option specifies the expiry time for negative callout cache data for an
14501 address. See section &<<SECTcallver>>& for details of callout verification, and
14502 section &<<SECTcallvercache>>& for details of the caching.
14505 .option callout_positive_expire main time 24h
14506 This option specifies the expiry time for positive callout cache data for an
14507 address. See section &<<SECTcallver>>& for details of callout verification, and
14508 section &<<SECTcallvercache>>& for details of the caching.
14511 .option callout_random_local_part main string&!! "see below"
14512 This option defines the &"random"& local part that can be used as part of
14513 callout verification. The default value is
14515 $primary_hostname-$tod_epoch-testing
14517 See section &<<CALLaddparcall>>& for details of how this value is used.
14520 .option check_log_inodes main integer 100
14521 See &%check_spool_space%& below.
14524 .option check_log_space main integer 10M
14525 See &%check_spool_space%& below.
14527 .oindex "&%check_rfc2047_length%&"
14528 .cindex "RFC 2047" "disabling length check"
14529 .option check_rfc2047_length main boolean true
14530 RFC 2047 defines a way of encoding non-ASCII characters in headers using a
14531 system of &"encoded words"&. The RFC specifies a maximum length for an encoded
14532 word; strings to be encoded that exceed this length are supposed to use
14533 multiple encoded words. By default, Exim does not recognize encoded words that
14534 exceed the maximum length. However, it seems that some software, in violation
14535 of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is
14536 set false, Exim recognizes encoded words of any length.
14539 .option check_spool_inodes main integer 100
14540 See &%check_spool_space%& below.
14543 .option check_spool_space main integer 10M
14544 .cindex "checking disk space"
14545 .cindex "disk space, checking"
14546 .cindex "spool directory" "checking space"
14547 The four &%check_...%& options allow for checking of disk resources before a
14548 message is accepted.
14550 .vindex "&$log_inodes$&"
14551 .vindex "&$log_space$&"
14552 .vindex "&$spool_inodes$&"
14553 .vindex "&$spool_space$&"
14554 When any of these options are nonzero, they apply to all incoming messages. If you
14555 want to apply different checks to different kinds of message, you can do so by
14556 testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and
14557 &$spool_space$& in an ACL with appropriate additional conditions.
14560 &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if
14561 either value is greater than zero, for example:
14563 check_spool_space = 100M
14564 check_spool_inodes = 100
14566 The spool partition is the one that contains the directory defined by
14567 SPOOL_DIRECTORY in &_Local/Makefile_&. It is used for holding messages in
14570 &%check_log_space%& and &%check_log_inodes%& check the partition in which log
14571 files are written if either is greater than zero. These should be set only if
14572 &%log_file_path%& and &%spool_directory%& refer to different partitions.
14574 If there is less space or fewer inodes than requested, Exim refuses to accept
14575 incoming mail. In the case of SMTP input this is done by giving a 452 temporary
14576 error response to the MAIL command. If ESMTP is in use and there was a
14577 SIZE parameter on the MAIL command, its value is added to the
14578 &%check_spool_space%& value, and the check is performed even if
14579 &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set.
14581 The values for &%check_spool_space%& and &%check_log_space%& are held as a
14582 number of kilobytes (though specified in bytes).
14583 If a non-multiple of 1024 is specified, it is rounded up.
14585 For non-SMTP input and for batched SMTP input, the test is done at start-up; on
14586 failure a message is written to stderr and Exim exits with a non-zero code, as
14587 it obviously cannot send an error message of any kind.
14589 There is a slight performance penalty for these checks.
14590 Versions of Exim preceding 4.88 had these disabled by default;
14591 high-rate installations confident they will never run out of resources
14592 may wish to deliberately disable them.
14594 .option chunking_advertise_hosts main "host list&!!" *
14595 .cindex CHUNKING advertisement
14596 .cindex "RFC 3030" "CHUNKING"
14597 The CHUNKING extension (RFC3030) will be advertised in the EHLO message to
14599 Hosts may use the BDAT command as an alternate to DATA.
14601 .option commandline_checks_require_admin main boolean &`false`&
14602 .cindex "restricting access to features"
14603 This option restricts various basic checking features to require an
14604 administrative user.
14605 This affects most of the &%-b*%& options, such as &%-be%&.
14607 .option debug_store main boolean &`false`&
14608 .cindex debugging "memory corruption"
14609 .cindex memory debugging
14610 This option, when true, enables extra checking in Exim's internal memory
14611 management. For use when a memory corruption issue is being investigated,
14612 it should normally be left as default.
14614 .option daemon_smtp_ports main string &`smtp`&
14615 .cindex "port" "for daemon"
14616 .cindex "TCP/IP" "setting listening ports"
14617 This option specifies one or more default SMTP ports on which the Exim daemon
14618 listens. See chapter &<<CHAPinterfaces>>& for details of how it is used. For
14619 backward compatibility, &%daemon_smtp_port%& (singular) is a synonym.
14621 .option daemon_startup_retries main integer 9
14622 .cindex "daemon startup, retrying"
14623 This option, along with &%daemon_startup_sleep%&, controls the retrying done by
14624 the daemon at startup when it cannot immediately bind a listening socket
14625 (typically because the socket is already in use): &%daemon_startup_retries%&
14626 defines the number of retries after the first failure, and
14627 &%daemon_startup_sleep%& defines the length of time to wait between retries.
14629 .option daemon_startup_sleep main time 30s
14630 See &%daemon_startup_retries%&.
14632 .option delay_warning main "time list" 24h
14633 .cindex "warning of delay"
14634 .cindex "delay warning, specifying"
14635 .cindex "queue" "delay warning"
14636 When a message is delayed, Exim sends a warning message to the sender at
14637 intervals specified by this option. The data is a colon-separated list of times
14638 after which to send warning messages. If the value of the option is an empty
14639 string or a zero time, no warnings are sent. Up to 10 times may be given. If a
14640 message has been on the queue for longer than the last time, the last interval
14641 between the times is used to compute subsequent warning times. For example,
14644 delay_warning = 4h:8h:24h
14646 the first message is sent after 4 hours, the second after 8 hours, and
14647 the third one after 24 hours. After that, messages are sent every 16 hours,
14648 because that is the interval between the last two times on the list. If you set
14649 just one time, it specifies the repeat interval. For example, with:
14653 messages are repeated every six hours. To stop warnings after a given time, set
14654 a very large time at the end of the list. For example:
14656 delay_warning = 2h:12h:99d
14658 Note that the option is only evaluated at the time a delivery attempt fails,
14659 which depends on retry and queue-runner configuration.
14660 Typically retries will be configured more frequently than warning messages.
14662 .option delay_warning_condition main string&!! "see below"
14663 .vindex "&$domain$&"
14664 The string is expanded at the time a warning message might be sent. If all the
14665 deferred addresses have the same domain, it is set in &$domain$& during the
14666 expansion. Otherwise &$domain$& is empty. If the result of the expansion is a
14667 forced failure, an empty string, or a string matching any of &"0"&, &"no"& or
14668 &"false"& (the comparison being done caselessly) then the warning message is
14669 not sent. The default is:
14671 delay_warning_condition = ${if or {\
14672 { !eq{$h_list-id:$h_list-post:$h_list-subscribe:}{} }\
14673 { match{$h_precedence:}{(?i)bulk|list|junk} }\
14674 { match{$h_auto-submitted:}{(?i)auto-generated|auto-replied} }\
14677 This suppresses the sending of warnings for messages that contain &'List-ID:'&,
14678 &'List-Post:'&, or &'List-Subscribe:'& headers, or have &"bulk"&, &"list"& or
14679 &"junk"& in a &'Precedence:'& header, or have &"auto-generated"& or
14680 &"auto-replied"& in an &'Auto-Submitted:'& header.
14682 .option deliver_drop_privilege main boolean false
14683 .cindex "unprivileged delivery"
14684 .cindex "delivery" "unprivileged"
14685 If this option is set true, Exim drops its root privilege at the start of a
14686 delivery process, and runs as the Exim user throughout. This severely restricts
14687 the kinds of local delivery that are possible, but is viable in certain types
14688 of configuration. There is a discussion about the use of root privilege in
14689 chapter &<<CHAPsecurity>>&.
14691 .option deliver_queue_load_max main fixed-point unset
14692 .cindex "load average"
14693 .cindex "queue runner" "abandoning"
14694 When this option is set, a queue run is abandoned if the system load average
14695 becomes greater than the value of the option. The option has no effect on
14696 ancient operating systems on which Exim cannot determine the load average.
14697 See also &%queue_only_load%& and &%smtp_load_reserve%&.
14700 .option delivery_date_remove main boolean true
14701 .cindex "&'Delivery-date:'& header line"
14702 Exim's transports have an option for adding a &'Delivery-date:'& header to a
14703 message when it is delivered, in exactly the same way as &'Return-path:'& is
14704 handled. &'Delivery-date:'& records the actual time of delivery. Such headers
14705 should not be present in incoming messages, and this option causes them to be
14706 removed at the time the message is received, to avoid any problems that might
14707 occur when a delivered message is subsequently sent on to some other recipient.
14709 .option disable_fsync main boolean false
14710 .cindex "&[fsync()]&, disabling"
14711 This option is available only if Exim was built with the compile-time option
14712 ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in
14713 a runtime configuration generates an &"unknown option"& error. You should not
14714 build Exim with ENABLE_DISABLE_FSYNC or set &%disable_fsync%& unless you
14715 really, really, really understand what you are doing. &'No pre-compiled
14716 distributions of Exim should ever make this option available.'&
14718 When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force
14719 updated files' data to be written to disc before continuing. Unexpected events
14720 such as crashes and power outages may cause data to be lost or scrambled.
14721 Here be Dragons. &*Beware.*&
14724 .option disable_ipv6 main boolean false
14725 .cindex "IPv6" "disabling"
14726 If this option is set true, even if the Exim binary has IPv6 support, no IPv6
14727 activities take place. AAAA records are never looked up, and any IPv6 addresses
14728 that are listed in &%local_interfaces%&, data for the &%manualroute%& router,
14729 etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines
14730 to handle IPv6 literal addresses.
14733 .option dkim_verify_signers main "domain list&!!" $dkim_signers
14734 .cindex DKIM "controlling calls to the ACL"
14735 This option gives a list of DKIM domains for which the DKIM ACL is run.
14736 It is expanded after the message is received; by default it runs
14737 the ACL once for each signature in the message.
14738 See section &<<SECDKIMVFY>>&.
14741 .option dns_again_means_nonexist main "domain list&!!" unset
14742 .cindex "DNS" "&""try again""& response; overriding"
14743 DNS lookups give a &"try again"& response for the DNS errors
14744 &"non-authoritative host not found"& and &"SERVERFAIL"&. This can cause Exim to
14745 keep trying to deliver a message, or to give repeated temporary errors to
14746 incoming mail. Sometimes the effect is caused by a badly set up name server and
14747 may persist for a long time. If a domain which exhibits this problem matches
14748 anything in &%dns_again_means_nonexist%&, it is treated as if it did not exist.
14749 This option should be used with care. You can make it apply to reverse lookups
14750 by a setting such as this:
14752 dns_again_means_nonexist = *.in-addr.arpa
14754 This option applies to all DNS lookups that Exim does. It also applies when the
14755 &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors,
14756 since these are most likely to be caused by DNS lookup problems. The
14757 &(dnslookup)& router has some options of its own for controlling what happens
14758 when lookups for MX or SRV records give temporary errors. These more specific
14759 options are applied after this global option.
14761 .option dns_check_names_pattern main string "see below"
14762 .cindex "DNS" "pre-check of name syntax"
14763 When this option is set to a non-empty string, it causes Exim to check domain
14764 names for characters that are not allowed in host names before handing them to
14765 the DNS resolver, because some resolvers give temporary errors for names that
14766 contain unusual characters. If a domain name contains any unwanted characters,
14767 a &"not found"& result is forced, and the resolver is not called. The check is
14768 done by matching the domain name against a regular expression, which is the
14769 value of this option. The default pattern is
14771 dns_check_names_pattern = \
14772 (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$
14774 which permits only letters, digits, slashes, and hyphens in components, but
14775 they must start and end with a letter or digit. Slashes are not, in fact,
14776 permitted in host names, but they are found in certain NS records (which can be
14777 accessed in Exim by using a &%dnsdb%& lookup). If you set
14778 &%allow_utf8_domains%&, you must modify this pattern, or set the option to an
14781 .option dns_csa_search_limit main integer 5
14782 This option controls the depth of parental searching for CSA SRV records in the
14783 DNS, as described in more detail in section &<<SECTverifyCSA>>&.
14785 .option dns_csa_use_reverse main boolean true
14786 This option controls whether or not an IP address, given as a CSA domain, is
14787 reversed and looked up in the reverse DNS, as described in more detail in
14788 section &<<SECTverifyCSA>>&.
14791 .option dns_cname_loops main integer 1
14792 .cindex DNS "CNAME following"
14793 This option controls the following of CNAME chains, needed if the resolver does
14794 not do it internally.
14795 As of 2018 most should, and the default can be left.
14796 If you have an ancient one, a value of 10 is likely needed.
14798 The default value of one CNAME-follow is needed
14799 thanks to the observed return for an MX request,
14800 given no MX presence but a CNAME to an A, of the CNAME.
14804 .option dns_dnssec_ok main integer -1
14805 .cindex "DNS" "resolver options"
14806 .cindex "DNS" "DNSSEC"
14807 If this option is set to a non-negative number then Exim will initialise the
14808 DNS resolver library to either use or not use DNSSEC, overriding the system
14809 default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on.
14811 If the resolver library does not support DNSSEC then this option has no effect.
14814 .option dns_ipv4_lookup main "domain list&!!" unset
14815 .cindex "IPv6" "DNS lookup for AAAA records"
14816 .cindex "DNS" "IPv6 lookup for AAAA records"
14817 .cindex DNS "IPv6 disabling"
14818 When Exim is compiled with IPv6 support and &%disable_ipv6%& is not set, it
14819 looks for IPv6 address records (AAAA records) as well as IPv4 address records
14820 (A records) when trying to find IP addresses for hosts, unless the host's
14821 domain matches this list.
14823 This is a fudge to help with name servers that give big delays or otherwise do
14824 not work for the AAAA record type. In due course, when the world's name
14825 servers have all been upgraded, there should be no need for this option.
14828 .option dns_retrans main time 0s
14829 .cindex "DNS" "resolver options"
14830 .cindex timeout "dns lookup"
14831 .cindex "DNS" timeout
14832 The options &%dns_retrans%& and &%dns_retry%& can be used to set the
14833 retransmission and retry parameters for DNS lookups. Values of zero (the
14834 defaults) leave the system default settings unchanged. The first value is the
14835 time between retries, and the second is the number of retries. It isn't
14836 totally clear exactly how these settings affect the total time a DNS lookup may
14837 take. I haven't found any documentation about timeouts on DNS lookups; these
14838 parameter values are available in the external resolver interface structure,
14839 but nowhere does it seem to describe how they are used or what you might want
14841 See also the &%slow_lookup_log%& option.
14844 .option dns_retry main integer 0
14845 See &%dns_retrans%& above.
14848 .option dns_trust_aa main "domain list&!!" unset
14849 .cindex "DNS" "resolver options"
14850 .cindex "DNS" "DNSSEC"
14851 If this option is set then lookup results marked with the AA bit
14852 (Authoritative Answer) are trusted the same way as if they were
14853 DNSSEC-verified. The authority section's name of the answer must
14854 match with this expanded domain list.
14856 Use this option only if you talk directly to a resolver that is
14857 authoritative for some zones and does not set the AD (Authentic Data)
14858 bit in the answer. Some DNS servers may have an configuration option to
14859 mark the answers from their own zones as verified (they set the AD bit).
14860 Others do not have this option. It is considered as poor practice using
14861 a resolver that is an authoritative server for some zones.
14863 Use this option only if you really have to (e.g. if you want
14864 to use DANE for remote delivery to a server that is listed in the DNS
14865 zones that your resolver is authoritative for).
14867 If the DNS answer packet has the AA bit set and contains resource record
14868 in the answer section, the name of the first NS record appearing in the
14869 authority section is compared against the list. If the answer packet is
14870 authoritative but the answer section is empty, the name of the first SOA
14871 record in the authoritative section is used instead.
14873 .cindex "DNS" "resolver options"
14874 .option dns_use_edns0 main integer -1
14875 .cindex "DNS" "resolver options"
14876 .cindex "DNS" "EDNS0"
14877 .cindex "DNS" "OpenBSD
14878 If this option is set to a non-negative number then Exim will initialise the
14879 DNS resolver library to either use or not use EDNS0 extensions, overriding
14880 the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0
14883 If the resolver library does not support EDNS0 then this option has no effect.
14885 OpenBSD's asr resolver routines are known to ignore the EDNS0 option; this
14886 means that DNSSEC will not work with Exim on that platform either, unless Exim
14887 is linked against an alternative DNS client library.
14890 .option drop_cr main boolean false
14891 This is an obsolete option that is now a no-op. It used to affect the way Exim
14892 handled CR and LF characters in incoming messages. What happens now is
14893 described in section &<<SECTlineendings>>&.
14895 .option dsn_advertise_hosts main "host list&!!" unset
14896 .cindex "bounce messages" "success"
14897 .cindex "DSN" "success"
14898 .cindex "Delivery Status Notification" "success"
14899 DSN extensions (RFC3461) will be advertised in the EHLO message to,
14900 and accepted from, these hosts.
14901 Hosts may use the NOTIFY and ENVID options on RCPT TO commands,
14902 and RET and ORCPT options on MAIL FROM commands.
14903 A NOTIFY=SUCCESS option requests success-DSN messages.
14904 A NOTIFY= option with no argument requests that no delay or failure DSNs
14907 .option dsn_from main "string&!!" "see below"
14908 .cindex "&'From:'& header line" "in bounces"
14909 .cindex "bounce messages" "&'From:'& line, specifying"
14910 This option can be used to vary the contents of &'From:'& header lines in
14911 bounces and other automatically generated messages (&"Delivery Status
14912 Notifications"& &-- hence the name of the option). The default setting is:
14914 dsn_from = Mail Delivery System <Mailer-Daemon@$qualify_domain>
14916 The value is expanded every time it is needed. If the expansion fails, a
14917 panic is logged, and the default value is used.
14919 .option envelope_to_remove main boolean true
14920 .cindex "&'Envelope-to:'& header line"
14921 Exim's transports have an option for adding an &'Envelope-to:'& header to a
14922 message when it is delivered, in exactly the same way as &'Return-path:'& is
14923 handled. &'Envelope-to:'& records the original recipient address from the
14924 message's envelope that caused the delivery to happen. Such headers should not
14925 be present in incoming messages, and this option causes them to be removed at
14926 the time the message is received, to avoid any problems that might occur when a
14927 delivered message is subsequently sent on to some other recipient.
14930 .option errors_copy main "string list&!!" unset
14931 .cindex "bounce message" "copy to other address"
14932 .cindex "copy of bounce message"
14933 Setting this option causes Exim to send bcc copies of bounce messages that it
14934 generates to other addresses. &*Note*&: This does not apply to bounce messages
14935 coming from elsewhere. The value of the option is a colon-separated list of
14936 items. Each item consists of a pattern, terminated by white space, followed by
14937 a comma-separated list of email addresses. If a pattern contains spaces, it
14938 must be enclosed in double quotes.
14940 Each pattern is processed in the same way as a single item in an address list
14941 (see section &<<SECTaddresslist>>&). When a pattern matches the recipient of
14942 the bounce message, the message is copied to the addresses on the list. The
14943 items are scanned in order, and once a matching one is found, no further items
14944 are examined. For example:
14946 errors_copy = spqr@mydomain postmaster@mydomain.example :\
14947 rqps@mydomain hostmaster@mydomain.example,\
14948 postmaster@mydomain.example
14950 .vindex "&$domain$&"
14951 .vindex "&$local_part$&"
14952 The address list is expanded before use. The expansion variables &$local_part$&
14953 and &$domain$& are set from the original recipient of the error message, and if
14954 there was any wildcard matching in the pattern, the expansion
14955 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%errors_copy%&"
14956 variables &$0$&, &$1$&, etc. are set in the normal way.
14959 .option errors_reply_to main string unset
14960 .cindex "bounce message" "&'Reply-to:'& in"
14961 By default, Exim's bounce and delivery warning messages contain the header line
14963 &`From: Mail Delivery System <Mailer-Daemon@`&&'qualify-domain'&&`>`&
14965 .oindex &%quota_warn_message%&
14966 where &'qualify-domain'& is the value of the &%qualify_domain%& option.
14967 A warning message that is generated by the &%quota_warn_message%& option in an
14968 &(appendfile)& transport may contain its own &'From:'& header line that
14969 overrides the default.
14971 Experience shows that people reply to bounce messages. If the
14972 &%errors_reply_to%& option is set, a &'Reply-To:'& header is added to bounce
14973 and warning messages. For example:
14975 errors_reply_to = postmaster@my.domain.example
14977 The value of the option is not expanded. It must specify a valid RFC 2822
14978 address. However, if a warning message that is generated by the
14979 &%quota_warn_message%& option in an &(appendfile)& transport contain its
14980 own &'Reply-To:'& header line, the value of the &%errors_reply_to%& option is
14984 .option event_action main string&!! unset
14986 This option declares a string to be expanded for Exim's events mechanism.
14987 For details see chapter &<<CHAPevents>>&.
14990 .option exim_group main string "compile-time configured"
14991 .cindex "gid (group id)" "Exim's own"
14992 .cindex "Exim group"
14993 This option changes the gid under which Exim runs when it gives up root
14994 privilege. The default value is compiled into the binary. The value of this
14995 option is used only when &%exim_user%& is also set. Unless it consists entirely
14996 of digits, the string is looked up using &[getgrnam()]&, and failure causes a
14997 configuration error. See chapter &<<CHAPsecurity>>& for a discussion of
15001 .option exim_path main string "see below"
15002 .cindex "Exim binary, path name"
15003 This option specifies the path name of the Exim binary, which is used when Exim
15004 needs to re-exec itself. The default is set up to point to the file &'exim'& in
15005 the directory configured at compile time by the BIN_DIRECTORY setting. It
15006 is necessary to change &%exim_path%& if, exceptionally, Exim is run from some
15008 &*Warning*&: Do not use a macro to define the value of this option, because
15009 you will break those Exim utilities that scan the configuration file to find
15010 where the binary is. (They then use the &%-bP%& option to extract option
15011 settings such as the value of &%spool_directory%&.)
15014 .option exim_user main string "compile-time configured"
15015 .cindex "uid (user id)" "Exim's own"
15016 .cindex "Exim user"
15017 This option changes the uid under which Exim runs when it gives up root
15018 privilege. The default value is compiled into the binary. Ownership of the run
15019 time configuration file and the use of the &%-C%& and &%-D%& command line
15020 options is checked against the values in the binary, not what is set here.
15022 Unless it consists entirely of digits, the string is looked up using
15023 &[getpwnam()]&, and failure causes a configuration error. If &%exim_group%& is
15024 not also supplied, the gid is taken from the result of &[getpwnam()]& if it is
15025 used. See chapter &<<CHAPsecurity>>& for a discussion of security issues.
15028 .option extra_local_interfaces main "string list" unset
15029 This option defines network interfaces that are to be considered local when
15030 routing, but which are not used for listening by the daemon. See section
15031 &<<SECTreclocipadd>>& for details.
15034 . Allow this long option name to split; give it unsplit as a fifth argument
15035 . for the automatic .oindex that is generated by .option.
15037 .option "extract_addresses_remove_arguments" main boolean true &&&
15038 extract_addresses_remove_arguments
15040 .cindex "command line" "addresses with &%-t%&"
15041 .cindex "Sendmail compatibility" "&%-t%& option"
15042 According to some Sendmail documentation (Sun, IRIX, HP-UX), if any addresses
15043 are present on the command line when the &%-t%& option is used to build an
15044 envelope from a message's &'To:'&, &'Cc:'& and &'Bcc:'& headers, the command
15045 line addresses are removed from the recipients list. This is also how Smail
15046 behaves. However, other Sendmail documentation (the O'Reilly book) states that
15047 command line addresses are added to those obtained from the header lines. When
15048 &%extract_addresses_remove_arguments%& is true (the default), Exim subtracts
15049 argument headers. If it is set false, Exim adds rather than removes argument
15053 .option finduser_retries main integer 0
15054 .cindex "NIS, retrying user lookups"
15055 On systems running NIS or other schemes in which user and group information is
15056 distributed from a remote system, there can be times when &[getpwnam()]& and
15057 related functions fail, even when given valid data, because things time out.
15058 Unfortunately these failures cannot be distinguished from genuine &"not found"&
15059 errors. If &%finduser_retries%& is set greater than zero, Exim will try that
15060 many extra times to find a user or a group, waiting for one second between
15063 .cindex "&_/etc/passwd_&" "multiple reading of"
15064 You should not set this option greater than zero if your user information is in
15065 a traditional &_/etc/passwd_& file, because it will cause Exim needlessly to
15066 search the file multiple times for non-existent users, and also cause delay.
15070 .option freeze_tell main "string list, comma separated" unset
15071 .cindex "freezing messages" "sending a message when freezing"
15072 On encountering certain errors, or when configured to do so in a system filter,
15073 ACL, or special router, Exim freezes a message. This means that no further
15074 delivery attempts take place until an administrator thaws the message, or the
15075 &%auto_thaw%&, &%ignore_bounce_errors_after%&, or &%timeout_frozen_after%&
15076 feature cause it to be processed. If &%freeze_tell%& is set, Exim generates a
15077 warning message whenever it freezes something, unless the message it is
15078 freezing is a locally-generated bounce message. (Without this exception there
15079 is the possibility of looping.) The warning message is sent to the addresses
15080 supplied as the comma-separated value of this option. If several of the
15081 message's addresses cause freezing, only a single message is sent. If the
15082 freezing was automatic, the reason(s) for freezing can be found in the message
15083 log. If you configure freezing in a filter or ACL, you must arrange for any
15084 logging that you require.
15087 .option gecos_name main string&!! unset
15089 .cindex "&""gecos""& field, parsing"
15090 Some operating systems, notably HP-UX, use the &"gecos"& field in the system
15091 password file to hold other information in addition to users' real names. Exim
15092 looks up this field for use when it is creating &'Sender:'& or &'From:'&
15093 headers. If either &%gecos_pattern%& or &%gecos_name%& are unset, the contents
15094 of the field are used unchanged, except that, if an ampersand is encountered,
15095 it is replaced by the user's login name with the first character forced to
15096 upper case, since this is a convention that is observed on many systems.
15098 When these options are set, &%gecos_pattern%& is treated as a regular
15099 expression that is to be applied to the field (again with && replaced by the
15100 login name), and if it matches, &%gecos_name%& is expanded and used as the
15103 .cindex "numerical variables (&$1$& &$2$& etc)" "in &%gecos_name%&"
15104 Numeric variables such as &$1$&, &$2$&, etc. can be used in the expansion to
15105 pick up sub-fields that were matched by the pattern. In HP-UX, where the user's
15106 name terminates at the first comma, the following can be used:
15108 gecos_pattern = ([^,]*)
15112 .option gecos_pattern main string unset
15113 See &%gecos_name%& above.
15116 .option gnutls_compat_mode main boolean unset
15117 This option controls whether GnuTLS is used in compatibility mode in an Exim
15118 server. This reduces security slightly, but improves interworking with older
15119 implementations of TLS.
15122 .option gnutls_allow_auto_pkcs11 main boolean unset
15123 This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with
15124 the p11-kit configuration files in &_/etc/pkcs11/modules/_&.
15127 &url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs)
15132 .option headers_charset main string "see below"
15133 This option sets a default character set for translating from encoded MIME
15134 &"words"& in header lines, when referenced by an &$h_xxx$& expansion item. The
15135 default is the value of HEADERS_CHARSET in &_Local/Makefile_&. The
15136 ultimate default is ISO-8859-1. For more details see the description of header
15137 insertions in section &<<SECTexpansionitems>>&.
15141 .option header_maxsize main integer "see below"
15142 .cindex "header section" "maximum size of"
15143 .cindex "limit" "size of message header section"
15144 This option controls the overall maximum size of a message's header
15145 section. The default is the value of HEADER_MAXSIZE in
15146 &_Local/Makefile_&; the default for that is 1M. Messages with larger header
15147 sections are rejected.
15150 .option header_line_maxsize main integer 0
15151 .cindex "header lines" "maximum size of"
15152 .cindex "limit" "size of one header line"
15153 This option limits the length of any individual header line in a message, after
15154 all the continuations have been joined together. Messages with individual
15155 header lines that are longer than the limit are rejected. The default value of
15156 zero means &"no limit"&.
15161 .option helo_accept_junk_hosts main "host list&!!" unset
15162 .cindex "HELO" "accepting junk data"
15163 .cindex "EHLO" "accepting junk data"
15164 Exim checks the syntax of HELO and EHLO commands for incoming SMTP
15165 mail, and gives an error response for invalid data. Unfortunately, there are
15166 some SMTP clients that send syntactic junk. They can be accommodated by setting
15167 this option. Note that this is a syntax check only. See &%helo_verify_hosts%&
15168 if you want to do semantic checking.
15169 See also &%helo_allow_chars%& for a way of extending the permitted character
15173 .option helo_allow_chars main string unset
15174 .cindex "HELO" "underscores in"
15175 .cindex "EHLO" "underscores in"
15176 .cindex "underscore in EHLO/HELO"
15177 This option can be set to a string of rogue characters that are permitted in
15178 all EHLO and HELO names in addition to the standard letters, digits,
15179 hyphens, and dots. If you really must allow underscores, you can set
15181 helo_allow_chars = _
15183 Note that the value is one string, not a list.
15186 .option helo_lookup_domains main "domain list&!!" &`@:@[]`&
15187 .cindex "HELO" "forcing reverse lookup"
15188 .cindex "EHLO" "forcing reverse lookup"
15189 If the domain given by a client in a HELO or EHLO command matches this
15190 list, a reverse lookup is done in order to establish the host's true name. The
15191 default forces a lookup if the client host gives the server's name or any of
15192 its IP addresses (in brackets), something that broken clients have been seen to
15196 .option helo_try_verify_hosts main "host list&!!" unset
15197 .cindex "HELO verifying" "optional"
15198 .cindex "EHLO" "verifying, optional"
15199 By default, Exim just checks the syntax of HELO and EHLO commands (see
15200 &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like
15201 to do more extensive checking of the data supplied by these commands. The ACL
15202 condition &`verify = helo`& is provided to make this possible.
15203 Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&)
15204 to force the check to occur. From release 4.53 onwards, this is no longer
15205 necessary. If the check has not been done before &`verify = helo`& is
15206 encountered, it is done at that time. Consequently, this option is obsolete.
15207 Its specification is retained here for backwards compatibility.
15209 When an EHLO or HELO command is received, if the calling host matches
15210 &%helo_try_verify_hosts%&, Exim checks that the host name given in the HELO or
15211 EHLO command either:
15214 is an IP literal matching the calling address of the host, or
15216 .cindex "DNS" "reverse lookup"
15217 .cindex "reverse DNS lookup"
15218 matches the host name that Exim obtains by doing a reverse lookup of the
15219 calling host address, or
15221 when looked up in DNS yields the calling host address.
15224 However, the EHLO or HELO command is not rejected if any of the checks
15225 fail. Processing continues, but the result of the check is remembered, and can
15226 be detected later in an ACL by the &`verify = helo`& condition.
15228 If DNS was used for successful verification, the variable
15229 .cindex "DNS" "DNSSEC"
15230 &$helo_verify_dnssec$& records the DNSSEC status of the lookups.
15232 .option helo_verify_hosts main "host list&!!" unset
15233 .cindex "HELO verifying" "mandatory"
15234 .cindex "EHLO" "verifying, mandatory"
15235 Like &%helo_try_verify_hosts%&, this option is obsolete, and retained only for
15236 backwards compatibility. For hosts that match this option, Exim checks the host
15237 name given in the HELO or EHLO in the same way as for
15238 &%helo_try_verify_hosts%&. If the check fails, the HELO or EHLO command is
15239 rejected with a 550 error, and entries are written to the main and reject logs.
15240 If a MAIL command is received before EHLO or HELO, it is rejected with a 503
15243 .option hold_domains main "domain list&!!" unset
15244 .cindex "domain" "delaying delivery"
15245 .cindex "delivery" "delaying certain domains"
15246 This option allows mail for particular domains to be held on the queue
15247 manually. The option is overridden if a message delivery is forced with the
15248 &%-M%&, &%-qf%&, &%-Rf%& or &%-Sf%& options, and also while testing or
15249 verifying addresses using &%-bt%& or &%-bv%&. Otherwise, if a domain matches an
15250 item in &%hold_domains%&, no routing or delivery for that address is done, and
15251 it is deferred every time the message is looked at.
15253 This option is intended as a temporary operational measure for delaying the
15254 delivery of mail while some problem is being sorted out, or some new
15255 configuration tested. If you just want to delay the processing of some
15256 domains until a queue run occurs, you should use &%queue_domains%& or
15257 &%queue_smtp_domains%&, not &%hold_domains%&.
15259 A setting of &%hold_domains%& does not override Exim's code for removing
15260 messages from the queue if they have been there longer than the longest retry
15261 time in any retry rule. If you want to hold messages for longer than the normal
15262 retry times, insert a dummy retry rule with a long retry time.
15265 .option host_lookup main "host list&!!" unset
15266 .cindex "host name" "lookup, forcing"
15267 Exim does not look up the name of a calling host from its IP address unless it
15268 is required to compare against some host list, or the host matches
15269 &%helo_try_verify_hosts%& or &%helo_verify_hosts%&, or the host matches this
15270 option (which normally contains IP addresses rather than host names). The
15271 default configuration file contains
15275 which causes a lookup to happen for all hosts. If the expense of these lookups
15276 is felt to be too great, the setting can be changed or removed.
15278 After a successful reverse lookup, Exim does a forward lookup on the name it
15279 has obtained, to verify that it yields the IP address that it started with. If
15280 this check fails, Exim behaves as if the name lookup failed.
15282 .vindex "&$host_lookup_failed$&"
15283 .vindex "&$sender_host_name$&"
15284 After any kind of failure, the host name (in &$sender_host_name$&) remains
15285 unset, and &$host_lookup_failed$& is set to the string &"1"&. See also
15286 &%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and
15287 &`verify = reverse_host_lookup`& in ACLs.
15290 .option host_lookup_order main "string list" &`bydns:byaddr`&
15291 This option specifies the order of different lookup methods when Exim is trying
15292 to find a host name from an IP address. The default is to do a DNS lookup
15293 first, and then to try a local lookup (using &[gethostbyaddr()]& or equivalent)
15294 if that fails. You can change the order of these lookups, or omit one entirely,
15297 &*Warning*&: The &"byaddr"& method does not always yield aliases when there are
15298 multiple PTR records in the DNS and the IP address is not listed in
15299 &_/etc/hosts_&. Different operating systems give different results in this
15300 case. That is why the default tries a DNS lookup first.
15304 .option host_reject_connection main "host list&!!" unset
15305 .cindex "host" "rejecting connections from"
15306 If this option is set, incoming SMTP calls from the hosts listed are rejected
15307 as soon as the connection is made.
15308 This option is obsolete, and retained only for backward compatibility, because
15309 nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming
15310 connections immediately.
15312 The ability to give an immediate rejection (either by this option or using an
15313 ACL) is provided for use in unusual cases. Many hosts will just try again,
15314 sometimes without much delay. Normally, it is better to use an ACL to reject
15315 incoming messages at a later stage, such as after RCPT commands. See
15316 chapter &<<CHAPACL>>&.
15319 .option hosts_connection_nolog main "host list&!!" unset
15320 .cindex "host" "not logging connections from"
15321 This option defines a list of hosts for which connection logging does not
15322 happen, even though the &%smtp_connection%& log selector is set. For example,
15323 you might want not to log SMTP connections from local processes, or from
15324 127.0.0.1, or from your local LAN. This option is consulted in the main loop of
15325 the daemon; you should therefore strive to restrict its value to a short inline
15326 list of IP addresses and networks. To disable logging SMTP connections from
15327 local processes, you must create a host list with an empty item. For example:
15329 hosts_connection_nolog = :
15331 If the &%smtp_connection%& log selector is not set, this option has no effect.
15335 .option hosts_proxy main "host list&!!" unset
15336 .cindex proxy "proxy protocol"
15337 This option enables use of Proxy Protocol proxies for incoming
15338 connections. For details see section &<<SECTproxyInbound>>&.
15341 .option hosts_treat_as_local main "domain list&!!" unset
15342 .cindex "local host" "domains treated as"
15343 .cindex "host" "treated as local"
15344 If this option is set, any host names that match the domain list are treated as
15345 if they were the local host when Exim is scanning host lists obtained from MX
15347 or other sources. Note that the value of this option is a domain list, not a
15348 host list, because it is always used to check host names, not IP addresses.
15350 This option also applies when Exim is matching the special items
15351 &`@mx_any`&, &`@mx_primary`&, and &`@mx_secondary`& in a domain list (see
15352 section &<<SECTdomainlist>>&), and when checking the &%hosts%& option in the
15353 &(smtp)& transport for the local host (see the &%allow_localhost%& option in
15354 that transport). See also &%local_interfaces%&, &%extra_local_interfaces%&, and
15355 chapter &<<CHAPinterfaces>>&, which contains a discussion about local network
15356 interfaces and recognizing the local host.
15359 .option ibase_servers main "string list" unset
15360 .cindex "InterBase" "server list"
15361 This option provides a list of InterBase servers and associated connection data,
15362 to be used in conjunction with &(ibase)& lookups (see section &<<SECID72>>&).
15363 The option is available only if Exim has been built with InterBase support.
15367 .option ignore_bounce_errors_after main time 10w
15368 .cindex "bounce message" "discarding"
15369 .cindex "discarding bounce message"
15370 This option affects the processing of bounce messages that cannot be delivered,
15371 that is, those that suffer a permanent delivery failure. (Bounce messages that
15372 suffer temporary delivery failures are of course retried in the usual way.)
15374 After a permanent delivery failure, bounce messages are frozen,
15375 because there is no sender to whom they can be returned. When a frozen bounce
15376 message has been on the queue for more than the given time, it is unfrozen at
15377 the next queue run, and a further delivery is attempted. If delivery fails
15378 again, the bounce message is discarded. This makes it possible to keep failed
15379 bounce messages around for a shorter time than the normal maximum retry time
15380 for frozen messages. For example,
15382 ignore_bounce_errors_after = 12h
15384 retries failed bounce message deliveries after 12 hours, discarding any further
15385 failures. If the value of this option is set to a zero time period, bounce
15386 failures are discarded immediately. Setting a very long time (as in the default
15387 value) has the effect of disabling this option. For ways of automatically
15388 dealing with other kinds of frozen message, see &%auto_thaw%& and
15389 &%timeout_frozen_after%&.
15392 .option ignore_fromline_hosts main "host list&!!" unset
15393 .cindex "&""From""& line"
15394 .cindex "UUCP" "&""From""& line"
15395 Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before
15396 the headers of a message. By default this is treated as the start of the
15397 message's body, which means that any following headers are not recognized as
15398 such. Exim can be made to ignore it by setting &%ignore_fromline_hosts%& to
15399 match those hosts that insist on sending it. If the sender is actually a local
15400 process rather than a remote host, and is using &%-bs%& to inject the messages,
15401 &%ignore_fromline_local%& must be set to achieve this effect.
15404 .option ignore_fromline_local main boolean false
15405 See &%ignore_fromline_hosts%& above.
15407 .option keep_environment main "string list" unset
15408 .cindex "environment" "values from"
15409 This option contains a string list of environment variables to keep.
15410 You have to trust these variables or you have to be sure that
15411 these variables do not impose any security risk. Keep in mind that
15412 during the startup phase Exim is running with an effective UID 0 in most
15413 installations. As the default value is an empty list, the default
15414 environment for using libraries, running embedded Perl code, or running
15415 external binaries is empty, and does not not even contain PATH or HOME.
15417 Actually the list is interpreted as a list of patterns
15418 (&<<SECTlistexpand>>&), except that it is not expanded first.
15420 WARNING: Macro substitution is still done first, so having a macro
15421 FOO and having FOO_HOME in your &%keep_environment%& option may have
15422 unexpected results. You may work around this using a regular expression
15423 that does not match the macro name: ^[F]OO_HOME$.
15425 Current versions of Exim issue a warning during startup if you do not mention
15426 &%keep_environment%& in your runtime configuration file and if your
15427 current environment is not empty. Future versions may not issue that warning
15430 See the &%add_environment%& main config option for a way to set
15431 environment variables to a fixed value. The environment for &(pipe)&
15432 transports is handled separately, see section &<<SECTpipeenv>>& for
15436 .option keep_malformed main time 4d
15437 This option specifies the length of time to keep messages whose spool files
15438 have been corrupted in some way. This should, of course, never happen. At the
15439 next attempt to deliver such a message, it gets removed. The incident is
15443 .option ldap_ca_cert_dir main string unset
15444 .cindex "LDAP", "TLS CA certificate directory"
15445 .cindex certificate "directory for LDAP"
15446 This option indicates which directory contains CA certificates for verifying
15447 a TLS certificate presented by an LDAP server.
15448 While Exim does not provide a default value, your SSL library may.
15449 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
15450 and constrained to be a directory.
15453 .option ldap_ca_cert_file main string unset
15454 .cindex "LDAP", "TLS CA certificate file"
15455 .cindex certificate "file for LDAP"
15456 This option indicates which file contains CA certificates for verifying
15457 a TLS certificate presented by an LDAP server.
15458 While Exim does not provide a default value, your SSL library may.
15459 Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP
15460 and constrained to be a file.
15463 .option ldap_cert_file main string unset
15464 .cindex "LDAP" "TLS client certificate file"
15465 .cindex certificate "file for LDAP"
15466 This option indicates which file contains an TLS client certificate which
15467 Exim should present to the LDAP server during TLS negotiation.
15468 Should be used together with &%ldap_cert_key%&.
15471 .option ldap_cert_key main string unset
15472 .cindex "LDAP" "TLS client key file"
15473 .cindex certificate "key for LDAP"
15474 This option indicates which file contains the secret/private key to use
15475 to prove identity to the LDAP server during TLS negotiation.
15476 Should be used together with &%ldap_cert_file%&, which contains the
15477 identity to be proven.
15480 .option ldap_cipher_suite main string unset
15481 .cindex "LDAP" "TLS cipher suite"
15482 This controls the TLS cipher-suite negotiation during TLS negotiation with
15483 the LDAP server. See &<<SECTreqciphssl>>& for more details of the format of
15484 cipher-suite options with OpenSSL (as used by LDAP client libraries).
15487 .option ldap_default_servers main "string list" unset
15488 .cindex "LDAP" "default servers"
15489 This option provides a list of LDAP servers which are tried in turn when an
15490 LDAP query does not contain a server. See section &<<SECTforldaque>>& for
15491 details of LDAP queries. This option is available only when Exim has been built
15495 .option ldap_require_cert main string unset.
15496 .cindex "LDAP" "policy for LDAP server TLS cert presentation"
15497 This should be one of the values "hard", "demand", "allow", "try" or "never".
15498 A value other than one of these is interpreted as "never".
15499 See the entry "TLS_REQCERT" in your system man page for ldap.conf(5).
15500 Although Exim does not set a default, the LDAP library probably defaults
15504 .option ldap_start_tls main boolean false
15505 .cindex "LDAP" "whether or not to negotiate TLS"
15506 If set, Exim will attempt to negotiate TLS with the LDAP server when
15507 connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's
15508 "STARTTLS". This is distinct from using "ldaps", which is the LDAP form
15510 In the event of failure to negotiate TLS, the action taken is controlled
15511 by &%ldap_require_cert%&.
15512 This option is ignored for &`ldapi`& connections.
15515 .option ldap_version main integer unset
15516 .cindex "LDAP" "protocol version, forcing"
15517 This option can be used to force Exim to set a specific protocol version for
15518 LDAP. If it option is unset, it is shown by the &%-bP%& command line option as
15519 -1. When this is the case, the default is 3 if LDAP_VERSION3 is defined in
15520 the LDAP headers; otherwise it is 2. This option is available only when Exim
15521 has been built with LDAP support.
15525 .option local_from_check main boolean true
15526 .cindex "&'Sender:'& header line" "disabling addition of"
15527 .cindex "&'From:'& header line" "disabling checking of"
15528 When a message is submitted locally (that is, not over a TCP/IP connection) by
15529 an untrusted user, Exim removes any existing &'Sender:'& header line, and
15530 checks that the &'From:'& header line matches the login of the calling user and
15531 the domain specified by &%qualify_domain%&.
15533 &*Note*&: An unqualified address (no domain) in the &'From:'& header in a
15534 locally submitted message is automatically qualified by Exim, unless the
15535 &%-bnq%& command line option is used.
15537 You can use &%local_from_prefix%& and &%local_from_suffix%& to permit affixes
15538 on the local part. If the &'From:'& header line does not match, Exim adds a
15539 &'Sender:'& header with an address constructed from the calling user's login
15540 and the default qualify domain.
15542 If &%local_from_check%& is set false, the &'From:'& header check is disabled,
15543 and no &'Sender:'& header is ever added. If, in addition, you want to retain
15544 &'Sender:'& header lines supplied by untrusted users, you must also set
15545 &%local_sender_retain%& to be true.
15547 .cindex "envelope sender"
15548 These options affect only the header lines in the message. The envelope sender
15549 is still forced to be the login id at the qualify domain unless
15550 &%untrusted_set_sender%& permits the user to supply an envelope sender.
15552 For messages received over TCP/IP, an ACL can specify &"submission mode"& to
15553 request similar header line checking. See section &<<SECTthesenhea>>&, which
15554 has more details about &'Sender:'& processing.
15559 .option local_from_prefix main string unset
15560 When Exim checks the &'From:'& header line of locally submitted messages for
15561 matching the login id (see &%local_from_check%& above), it can be configured to
15562 ignore certain prefixes and suffixes in the local part of the address. This is
15563 done by setting &%local_from_prefix%& and/or &%local_from_suffix%& to
15564 appropriate lists, in the same form as the &%local_part_prefix%& and
15565 &%local_part_suffix%& router options (see chapter &<<CHAProutergeneric>>&). For
15568 local_from_prefix = *-
15570 is set, a &'From:'& line containing
15572 From: anything-user@your.domain.example
15574 will not cause a &'Sender:'& header to be added if &'user@your.domain.example'&
15575 matches the actual sender address that is constructed from the login name and
15579 .option local_from_suffix main string unset
15580 See &%local_from_prefix%& above.
15583 .option local_interfaces main "string list" "see below"
15584 This option controls which network interfaces are used by the daemon for
15585 listening; they are also used to identify the local host when routing. Chapter
15586 &<<CHAPinterfaces>>& contains a full description of this option and the related
15587 options &%daemon_smtp_ports%&, &%extra_local_interfaces%&,
15588 &%hosts_treat_as_local%&, and &%tls_on_connect_ports%&. The default value for
15589 &%local_interfaces%& is
15591 local_interfaces = 0.0.0.0
15593 when Exim is built without IPv6 support; otherwise it is
15595 local_interfaces = <; ::0 ; 0.0.0.0
15598 .option local_scan_timeout main time 5m
15599 .cindex "timeout" "for &[local_scan()]& function"
15600 .cindex "&[local_scan()]& function" "timeout"
15601 This timeout applies to the &[local_scan()]& function (see chapter
15602 &<<CHAPlocalscan>>&). Zero means &"no timeout"&. If the timeout is exceeded,
15603 the incoming message is rejected with a temporary error if it is an SMTP
15604 message. For a non-SMTP message, the message is dropped and Exim ends with a
15605 non-zero code. The incident is logged on the main and reject logs.
15609 .option local_sender_retain main boolean false
15610 .cindex "&'Sender:'& header line" "retaining from local submission"
15611 When a message is submitted locally (that is, not over a TCP/IP connection) by
15612 an untrusted user, Exim removes any existing &'Sender:'& header line. If you
15613 do not want this to happen, you must set &%local_sender_retain%&, and you must
15614 also set &%local_from_check%& to be false (Exim will complain if you do not).
15615 See also the ACL modifier &`control = suppress_local_fixups`&. Section
15616 &<<SECTthesenhea>>& has more details about &'Sender:'& processing.
15621 .option localhost_number main string&!! unset
15622 .cindex "host" "locally unique number for"
15623 .cindex "message ids" "with multiple hosts"
15624 .vindex "&$localhost_number$&"
15625 Exim's message ids are normally unique only within the local host. If
15626 uniqueness among a set of hosts is required, each host must set a different
15627 value for the &%localhost_number%& option. The string is expanded immediately
15628 after reading the configuration file (so that a number can be computed from the
15629 host name, for example) and the result of the expansion must be a number in the
15630 range 0&--16 (or 0&--10 on operating systems with case-insensitive file
15631 systems). This is available in subsequent string expansions via the variable
15632 &$localhost_number$&. When &%localhost_number is set%&, the final two
15633 characters of the message id, instead of just being a fractional part of the
15634 time, are computed from the time and the local host number as described in
15635 section &<<SECTmessiden>>&.
15639 .option log_file_path main "string list&!!" "set at compile time"
15640 .cindex "log" "file path for"
15641 This option sets the path which is used to determine the names of Exim's log
15642 files, or indicates that logging is to be to syslog, or both. It is expanded
15643 when Exim is entered, so it can, for example, contain a reference to the host
15644 name. If no specific path is set for the log files at compile or run time,
15645 or if the option is unset at run time (i.e. &`log_file_path = `&)
15646 they are written in a sub-directory called &_log_& in Exim's spool directory.
15647 Chapter &<<CHAPlog>>& contains further details about Exim's logging, and
15648 section &<<SECTwhelogwri>>& describes how the contents of &%log_file_path%& are
15649 used. If this string is fixed at your installation (contains no expansion
15650 variables) it is recommended that you do not set this option in the
15651 configuration file, but instead supply the path using LOG_FILE_PATH in
15652 &_Local/Makefile_& so that it is available to Exim for logging errors detected
15653 early on &-- in particular, failure to read the configuration file.
15656 .option log_selector main string unset
15657 .cindex "log" "selectors"
15658 This option can be used to reduce or increase the number of things that Exim
15659 writes to its log files. Its argument is made up of names preceded by plus or
15660 minus characters. For example:
15662 log_selector = +arguments -retry_defer
15664 A list of possible names and what they control is given in the chapter on
15665 logging, in section &<<SECTlogselector>>&.
15668 .option log_timezone main boolean false
15669 .cindex "log" "timezone for entries"
15670 .vindex "&$tod_log$&"
15671 .vindex "&$tod_zone$&"
15672 By default, the timestamps on log lines are in local time without the
15673 timezone. This means that if your timezone changes twice a year, the timestamps
15674 in log lines are ambiguous for an hour when the clocks go back. One way of
15675 avoiding this problem is to set the timezone to UTC. An alternative is to set
15676 &%log_timezone%& true. This turns on the addition of the timezone offset to
15677 timestamps in log lines. Turning on this option can add quite a lot to the size
15678 of log files because each line is extended by 6 characters. Note that the
15679 &$tod_log$& variable contains the log timestamp without the zone, but there is
15680 another variable called &$tod_zone$& that contains just the timezone offset.
15683 .option lookup_open_max main integer 25
15684 .cindex "too many open files"
15685 .cindex "open files, too many"
15686 .cindex "file" "too many open"
15687 .cindex "lookup" "maximum open files"
15688 .cindex "limit" "open files for lookups"
15689 This option limits the number of simultaneously open files for single-key
15690 lookups that use regular files (that is, &(lsearch)&, &(dbm)&, and &(cdb)&).
15691 Exim normally keeps these files open during routing, because often the same
15692 file is required several times. If the limit is reached, Exim closes the least
15693 recently used file. Note that if you are using the &'ndbm'& library, it
15694 actually opens two files for each logical DBM database, though it still counts
15695 as one for the purposes of &%lookup_open_max%&. If you are getting &"too many
15696 open files"& errors with NDBM, you need to reduce the value of
15697 &%lookup_open_max%&.
15700 .option max_username_length main integer 0
15701 .cindex "length of login name"
15702 .cindex "user name" "maximum length"
15703 .cindex "limit" "user name length"
15704 Some operating systems are broken in that they truncate long arguments to
15705 &[getpwnam()]& to eight characters, instead of returning &"no such user"&. If
15706 this option is set greater than zero, any attempt to call &[getpwnam()]& with
15707 an argument that is longer behaves as if &[getpwnam()]& failed.
15710 .option message_body_newlines main bool false
15711 .cindex "message body" "newlines in variables"
15712 .cindex "newline" "in message body variables"
15713 .vindex "&$message_body$&"
15714 .vindex "&$message_body_end$&"
15715 By default, newlines in the message body are replaced by spaces when setting
15716 the &$message_body$& and &$message_body_end$& expansion variables. If this
15717 option is set true, this no longer happens.
15720 .option message_body_visible main integer 500
15721 .cindex "body of message" "visible size"
15722 .cindex "message body" "visible size"
15723 .vindex "&$message_body$&"
15724 .vindex "&$message_body_end$&"
15725 This option specifies how much of a message's body is to be included in the
15726 &$message_body$& and &$message_body_end$& expansion variables.
15729 .option message_id_header_domain main string&!! unset
15730 .cindex "&'Message-ID:'& header line"
15731 If this option is set, the string is expanded and used as the right hand side
15732 (domain) of the &'Message-ID:'& header that Exim creates if a
15733 locally-originated incoming message does not have one. &"Locally-originated"&
15734 means &"not received over TCP/IP."&
15735 Otherwise, the primary host name is used.
15736 Only letters, digits, dot and hyphen are accepted; any other characters are
15737 replaced by hyphens. If the expansion is forced to fail, or if the result is an
15738 empty string, the option is ignored.
15741 .option message_id_header_text main string&!! unset
15742 If this variable is set, the string is expanded and used to augment the text of
15743 the &'Message-id:'& header that Exim creates if a locally-originated incoming
15744 message does not have one. The text of this header is required by RFC 2822 to
15745 take the form of an address. By default, Exim uses its internal message id as
15746 the local part, and the primary host name as the domain. If this option is set,
15747 it is expanded, and provided the expansion is not forced to fail, and does not
15748 yield an empty string, the result is inserted into the header immediately
15749 before the @, separated from the internal message id by a dot. Any characters
15750 that are illegal in an address are automatically converted into hyphens. This
15751 means that variables such as &$tod_log$& can be used, because the spaces and
15752 colons will become hyphens.
15755 .option message_logs main boolean true
15756 .cindex "message logs" "disabling"
15757 .cindex "log" "message log; disabling"
15758 If this option is turned off, per-message log files are not created in the
15759 &_msglog_& spool sub-directory. This reduces the amount of disk I/O required by
15760 Exim, by reducing the number of files involved in handling a message from a
15761 minimum of four (header spool file, body spool file, delivery journal, and
15762 per-message log) to three. The other major I/O activity is Exim's main log,
15763 which is not affected by this option.
15766 .option message_size_limit main string&!! 50M
15767 .cindex "message" "size limit"
15768 .cindex "limit" "message size"
15769 .cindex "size" "of message, limit"
15770 This option limits the maximum size of message that Exim will process. The
15771 value is expanded for each incoming connection so, for example, it can be made
15772 to depend on the IP address of the remote host for messages arriving via
15773 TCP/IP. After expansion, the value must be a sequence of decimal digits,
15774 optionally followed by K or M.
15776 &*Note*&: This limit cannot be made to depend on a message's sender or any
15777 other properties of an individual message, because it has to be advertised in
15778 the server's response to EHLO. String expansion failure causes a temporary
15779 error. A value of zero means no limit, but its use is not recommended. See also
15780 &%bounce_return_size_limit%&.
15782 Incoming SMTP messages are failed with a 552 error if the limit is
15783 exceeded; locally-generated messages either get a stderr message or a delivery
15784 failure message to the sender, depending on the &%-oe%& setting. Rejection of
15785 an oversized message is logged in both the main and the reject logs. See also
15786 the generic transport option &%message_size_limit%&, which limits the size of
15787 message that an individual transport can process.
15789 If you use a virus-scanner and set this option to to a value larger than the
15790 maximum size that your virus-scanner is configured to support, you may get
15791 failures triggered by large mails. The right size to configure for the
15792 virus-scanner depends upon what data is passed and the options in use but it's
15793 probably safest to just set it to a little larger than this value. E.g., with a
15794 default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M,
15795 some problems may result.
15797 A value of 0 will disable size limit checking; Exim will still advertise the
15798 SIZE extension in an EHLO response, but without a limit, so as to permit
15799 SMTP clients to still indicate the message size along with the MAIL verb.
15802 .option move_frozen_messages main boolean false
15803 .cindex "frozen messages" "moving"
15804 This option, which is available only if Exim has been built with the setting
15806 SUPPORT_MOVE_FROZEN_MESSAGES=yes
15808 in &_Local/Makefile_&, causes frozen messages and their message logs to be
15809 moved from the &_input_& and &_msglog_& directories on the spool to &_Finput_&
15810 and &_Fmsglog_&, respectively. There is currently no support in Exim or the
15811 standard utilities for handling such moved messages, and they do not show up in
15812 lists generated by &%-bp%& or by the Exim monitor.
15815 .option mua_wrapper main boolean false
15816 Setting this option true causes Exim to run in a very restrictive mode in which
15817 it passes messages synchronously to a smart host. Chapter &<<CHAPnonqueueing>>&
15818 contains a full description of this facility.
15822 .option mysql_servers main "string list" unset
15823 .cindex "MySQL" "server list"
15824 This option provides a list of MySQL servers and associated connection data, to
15825 be used in conjunction with &(mysql)& lookups (see section &<<SECID72>>&). The
15826 option is available only if Exim has been built with MySQL support.
15829 .option never_users main "string list&!!" unset
15830 This option is expanded just once, at the start of Exim's processing. Local
15831 message deliveries are normally run in processes that are setuid to the
15832 recipient, and remote deliveries are normally run under Exim's own uid and gid.
15833 It is usually desirable to prevent any deliveries from running as root, as a
15836 When Exim is built, an option called FIXED_NEVER_USERS can be set to a
15837 list of users that must not be used for local deliveries. This list is fixed in
15838 the binary and cannot be overridden by the configuration file. By default, it
15839 contains just the single user name &"root"&. The &%never_users%& runtime option
15840 can be used to add more users to the fixed list.
15842 If a message is to be delivered as one of the users on the fixed list or the
15843 &%never_users%& list, an error occurs, and delivery is deferred. A common
15846 never_users = root:daemon:bin
15848 Including root is redundant if it is also on the fixed list, but it does no
15849 harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)&
15853 .option openssl_options main "string list" "+no_sslv2 +single_dh_use +no_ticket"
15854 .cindex "OpenSSL "compatibility options"
15855 This option allows an administrator to adjust the SSL options applied
15856 by OpenSSL to connections. It is given as a space-separated list of items,
15857 each one to be +added or -subtracted from the current value.
15859 This option is only available if Exim is built against OpenSSL. The values
15860 available for this option vary according to the age of your OpenSSL install.
15861 The &"all"& value controls a subset of flags which are available, typically
15862 the bug workaround options. The &'SSL_CTX_set_options'& man page will
15863 list the values known on your system and Exim should support all the
15864 &"bug workaround"& options and many of the &"modifying"& options. The Exim
15865 names lose the leading &"SSL_OP_"& and are lower-cased.
15867 Note that adjusting the options can have severe impact upon the security of
15868 SSL as used by Exim. It is possible to disable safety checks and shoot
15869 yourself in the foot in various unpleasant ways. This option should not be
15870 adjusted lightly. An unrecognised item will be detected at startup, by
15871 invoking Exim with the &%-bV%& flag.
15873 The option affects Exim operating both as a server and as a client.
15875 Historical note: prior to release 4.80, Exim defaulted this value to
15876 "+dont_insert_empty_fragments", which may still be needed for compatibility
15877 with some clients, but which lowers security by increasing exposure to
15878 some now infamous attacks.
15882 # Make both old MS and old Eudora happy:
15883 openssl_options = -all +microsoft_big_sslv3_buffer \
15884 +dont_insert_empty_fragments
15886 # Disable older protocol versions:
15887 openssl_options = +no_sslv2 +no_sslv3
15890 Possible options may include:
15894 &`allow_unsafe_legacy_renegotiation`&
15896 &`cipher_server_preference`&
15898 &`dont_insert_empty_fragments`&
15902 &`legacy_server_connect`&
15904 &`microsoft_big_sslv3_buffer`&
15906 &`microsoft_sess_id_bug`&
15908 &`msie_sslv2_rsa_padding`&
15910 &`netscape_challenge_bug`&
15912 &`netscape_reuse_cipher_change_bug`&
15916 &`no_session_resumption_on_renegotiation`&
15930 &`safari_ecdhe_ecdsa_bug`&
15934 &`single_ecdh_use`&
15936 &`ssleay_080_client_dh_bug`&
15938 &`sslref2_reuse_cert_type_bug`&
15940 &`tls_block_padding_bug`&
15944 &`tls_rollback_bug`&
15947 As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects
15948 all clients connecting using the MacOS SecureTransport TLS facility prior
15949 to MacOS 10.8.4, including email clients. If you see old MacOS clients failing
15950 to negotiate TLS then this option value might help, provided that your OpenSSL
15951 release is new enough to contain this work-around. This may be a situation
15952 where you have to upgrade OpenSSL to get buggy clients working.
15955 .option oracle_servers main "string list" unset
15956 .cindex "Oracle" "server list"
15957 This option provides a list of Oracle servers and associated connection data,
15958 to be used in conjunction with &(oracle)& lookups (see section &<<SECID72>>&).
15959 The option is available only if Exim has been built with Oracle support.
15962 .option percent_hack_domains main "domain list&!!" unset
15963 .cindex "&""percent hack""&"
15964 .cindex "source routing" "in email address"
15965 .cindex "address" "source-routed"
15966 The &"percent hack"& is the convention whereby a local part containing a
15967 percent sign is re-interpreted as a new email address, with the percent
15968 replaced by @. This is sometimes called &"source routing"&, though that term is
15969 also applied to RFC 2822 addresses that begin with an @ character. If this
15970 option is set, Exim implements the percent facility for those domains listed,
15971 but no others. This happens before an incoming SMTP address is tested against
15974 &*Warning*&: The &"percent hack"& has often been abused by people who are
15975 trying to get round relaying restrictions. For this reason, it is best avoided
15976 if at all possible. Unfortunately, a number of less security-conscious MTAs
15977 implement it unconditionally. If you are running Exim on a gateway host, and
15978 routing mail through to internal MTAs without processing the local parts, it is
15979 a good idea to reject recipient addresses with percent characters in their
15980 local parts. Exim's default configuration does this.
15983 .option perl_at_start main boolean false
15985 This option is available only when Exim is built with an embedded Perl
15986 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15989 .option perl_startup main string unset
15991 This option is available only when Exim is built with an embedded Perl
15992 interpreter. See chapter &<<CHAPperl>>& for details of its use.
15994 .option perl_startup main boolean false
15996 This Option enables the taint mode of the embedded Perl interpreter.
15999 .option pgsql_servers main "string list" unset
16000 .cindex "PostgreSQL lookup type" "server list"
16001 This option provides a list of PostgreSQL servers and associated connection
16002 data, to be used in conjunction with &(pgsql)& lookups (see section
16003 &<<SECID72>>&). The option is available only if Exim has been built with
16004 PostgreSQL support.
16007 .option pid_file_path main string&!! "set at compile time"
16008 .cindex "daemon" "pid file path"
16009 .cindex "pid file, path for"
16010 This option sets the name of the file to which the Exim daemon writes its
16011 process id. The string is expanded, so it can contain, for example, references
16014 pid_file_path = /var/log/$primary_hostname/exim.pid
16016 If no path is set, the pid is written to the file &_exim-daemon.pid_& in Exim's
16018 The value set by the option can be overridden by the &%-oP%& command line
16019 option. A pid file is not written if a &"non-standard"& daemon is run by means
16020 of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&.
16023 .option pipelining_advertise_hosts main "host list&!!" *
16024 .cindex "PIPELINING" "suppressing advertising"
16025 This option can be used to suppress the advertisement of the SMTP
16026 PIPELINING extension to specific hosts. See also the &*no_pipelining*&
16027 control in section &<<SECTcontrols>>&. When PIPELINING is not advertised and
16028 &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization
16029 for each SMTP command and response. When PIPELINING is advertised, Exim assumes
16030 that clients will use it; &"out of order"& commands that are &"expected"& do
16031 not count as protocol errors (see &%smtp_max_synprot_errors%&).
16034 .option prdr_enable main boolean false
16035 .cindex "PRDR" "enabling on server"
16036 This option can be used to enable the Per-Recipient Data Response extension
16037 to SMTP, defined by Eric Hall.
16038 If the option is set, PRDR is advertised by Exim when operating as a server.
16039 If the client requests PRDR, and more than one recipient, for a message
16040 an additional ACL is called for each recipient after the message content
16041 is received. See section &<<SECTPRDRACL>>&.
16043 .option preserve_message_logs main boolean false
16044 .cindex "message logs" "preserving"
16045 If this option is set, message log files are not deleted when messages are
16046 completed. Instead, they are moved to a sub-directory of the spool directory
16047 called &_msglog.OLD_&, where they remain available for statistical or debugging
16048 purposes. This is a dangerous option to set on systems with any appreciable
16049 volume of mail. Use with care!
16052 .option primary_hostname main string "see below"
16053 .cindex "name" "of local host"
16054 .cindex "host" "name of local"
16055 .cindex "local host" "name of"
16056 .vindex "&$primary_hostname$&"
16057 This specifies the name of the current host. It is used in the default EHLO or
16058 HELO command for outgoing SMTP messages (changeable via the &%helo_data%&
16059 option in the &(smtp)& transport), and as the default for &%qualify_domain%&.
16060 The value is also used by default in some SMTP response messages from an Exim
16061 server. This can be changed dynamically by setting &%smtp_active_hostname%&.
16063 If &%primary_hostname%& is not set, Exim calls &[uname()]& to find the host
16064 name. If this fails, Exim panics and dies. If the name returned by &[uname()]&
16065 contains only one component, Exim passes it to &[gethostbyname()]& (or
16066 &[getipnodebyname()]& when available) in order to obtain the fully qualified
16067 version. The variable &$primary_hostname$& contains the host name, whether set
16068 explicitly by this option, or defaulted.
16071 .option print_topbitchars main boolean false
16072 .cindex "printing characters"
16073 .cindex "8-bit characters"
16074 By default, Exim considers only those characters whose codes lie in the range
16075 32&--126 to be printing characters. In a number of circumstances (for example,
16076 when writing log entries) non-printing characters are converted into escape
16077 sequences, primarily to avoid messing up the layout. If &%print_topbitchars%&
16078 is set, code values of 128 and above are also considered to be printing
16081 This option also affects the header syntax checks performed by the
16082 &(autoreply)& transport, and whether Exim uses RFC 2047 encoding of
16083 the user's full name when constructing From: and Sender: addresses (as
16084 described in section &<<SECTconstr>>&). Setting this option can cause
16085 Exim to generate eight bit message headers that do not conform to the
16089 .option process_log_path main string unset
16090 .cindex "process log path"
16091 .cindex "log" "process log"
16092 .cindex "&'exiwhat'&"
16093 This option sets the name of the file to which an Exim process writes its
16094 &"process log"& when sent a USR1 signal. This is used by the &'exiwhat'&
16095 utility script. If this option is unset, the file called &_exim-process.info_&
16096 in Exim's spool directory is used. The ability to specify the name explicitly
16097 can be useful in environments where two different Exims are running, using
16098 different spool directories.
16101 .option prod_requires_admin main boolean true
16102 .cindex "restricting access to features"
16106 The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
16107 admin user unless &%prod_requires_admin%& is set false. See also
16108 &%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
16111 .option qualify_domain main string "see below"
16112 .cindex "domain" "for qualifying addresses"
16113 .cindex "address" "qualification"
16114 This option specifies the domain name that is added to any envelope sender
16115 addresses that do not have a domain qualification. It also applies to
16116 recipient addresses if &%qualify_recipient%& is not set. Unqualified addresses
16117 are accepted by default only for locally-generated messages. Qualification is
16118 also applied to addresses in header lines such as &'From:'& and &'To:'& for
16119 locally-generated messages, unless the &%-bnq%& command line option is used.
16121 Messages from external sources must always contain fully qualified addresses,
16122 unless the sending host matches &%sender_unqualified_hosts%& or
16123 &%recipient_unqualified_hosts%& (as appropriate), in which case incoming
16124 addresses are qualified with &%qualify_domain%& or &%qualify_recipient%& as
16125 necessary. Internally, Exim always works with fully qualified envelope
16126 addresses. If &%qualify_domain%& is not set, it defaults to the
16127 &%primary_hostname%& value.
16130 .option qualify_recipient main string "see below"
16131 This option allows you to specify a different domain for qualifying recipient
16132 addresses to the one that is used for senders. See &%qualify_domain%& above.
16136 .option queue_domains main "domain list&!!" unset
16137 .cindex "domain" "specifying non-immediate delivery"
16138 .cindex "queueing incoming messages"
16139 .cindex "message" "queueing certain domains"
16140 This option lists domains for which immediate delivery is not required.
16141 A delivery process is started whenever a message is received, but only those
16142 domains that do not match are processed. All other deliveries wait until the
16143 next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
16146 .option queue_list_requires_admin main boolean true
16147 .cindex "restricting access to features"
16149 The &%-bp%& command-line option, which lists the messages that are on the
16150 queue, requires the caller to be an admin user unless
16151 &%queue_list_requires_admin%& is set false.
16152 See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
16155 .option queue_only main boolean false
16156 .cindex "queueing incoming messages"
16157 .cindex "message" "queueing unconditionally"
16158 If &%queue_only%& is set, a delivery process is not automatically started
16159 whenever a message is received. Instead, the message waits on the queue for the
16160 next queue run. Even if &%queue_only%& is false, incoming messages may not get
16161 delivered immediately when certain conditions (such as heavy load) occur.
16163 The &%-odq%& command line has the same effect as &%queue_only%&. The &%-odb%&
16164 and &%-odi%& command line options override &%queue_only%& unless
16165 &%queue_only_override%& is set false. See also &%queue_only_file%&,
16166 &%queue_only_load%&, and &%smtp_accept_queue%&.
16169 .option queue_only_file main string unset
16170 .cindex "queueing incoming messages"
16171 .cindex "message" "queueing by file existence"
16172 This option can be set to a colon-separated list of absolute path names, each
16173 one optionally preceded by &"smtp"&. When Exim is receiving a message,
16174 it tests for the existence of each listed path using a call to &[stat()]&. For
16175 each path that exists, the corresponding queueing option is set.
16176 For paths with no prefix, &%queue_only%& is set; for paths prefixed by
16177 &"smtp"&, &%queue_smtp_domains%& is set to match all domains. So, for example,
16179 queue_only_file = smtp/some/file
16181 causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever
16182 &_/some/file_& exists.
16185 .option queue_only_load main fixed-point unset
16186 .cindex "load average"
16187 .cindex "queueing incoming messages"
16188 .cindex "message" "queueing by load"
16189 If the system load average is higher than this value, incoming messages from
16190 all sources are queued, and no automatic deliveries are started. If this
16191 happens during local or remote SMTP input, all subsequent messages received on
16192 the same SMTP connection are queued by default, whatever happens to the load in
16193 the meantime, but this can be changed by setting &%queue_only_load_latch%&
16196 Deliveries will subsequently be performed by queue runner processes. This
16197 option has no effect on ancient operating systems on which Exim cannot
16198 determine the load average. See also &%deliver_queue_load_max%& and
16199 &%smtp_load_reserve%&.
16202 .option queue_only_load_latch main boolean true
16203 .cindex "load average" "re-evaluating per message"
16204 When this option is true (the default), once one message has been queued
16205 because the load average is higher than the value set by &%queue_only_load%&,
16206 all subsequent messages received on the same SMTP connection are also queued.
16207 This is a deliberate choice; even though the load average may fall below the
16208 threshold, it doesn't seem right to deliver later messages on the same
16209 connection when not delivering earlier ones. However, there are special
16210 circumstances such as very long-lived connections from scanning appliances
16211 where this is not the best strategy. In such cases, &%queue_only_load_latch%&
16212 should be set false. This causes the value of the load average to be
16213 re-evaluated for each message.
16216 .option queue_only_override main boolean true
16217 .cindex "queueing incoming messages"
16218 When this option is true, the &%-od%&&'x'& command line options override the
16219 setting of &%queue_only%& or &%queue_only_file%& in the configuration file. If
16220 &%queue_only_override%& is set false, the &%-od%&&'x'& options cannot be used
16221 to override; they are accepted, but ignored.
16224 .option queue_run_in_order main boolean false
16225 .cindex "queue runner" "processing messages in order"
16226 If this option is set, queue runs happen in order of message arrival instead of
16227 in an arbitrary order. For this to happen, a complete list of the entire queue
16228 must be set up before the deliveries start. When the queue is all held in a
16229 single directory (the default), a single list is created for both the ordered
16230 and the non-ordered cases. However, if &%split_spool_directory%& is set, a
16231 single list is not created when &%queue_run_in_order%& is false. In this case,
16232 the sub-directories are processed one at a time (in a random order), and this
16233 avoids setting up one huge list for the whole queue. Thus, setting
16234 &%queue_run_in_order%& with &%split_spool_directory%& may degrade performance
16235 when the queue is large, because of the extra work in setting up the single,
16236 large list. In most situations, &%queue_run_in_order%& should not be set.
16240 .option queue_run_max main integer&!! 5
16241 .cindex "queue runner" "maximum number of"
16242 This controls the maximum number of queue runner processes that an Exim daemon
16243 can run simultaneously. This does not mean that it starts them all at once,
16244 but rather that if the maximum number are still running when the time comes to
16245 start another one, it refrains from starting another one. This can happen with
16246 very large queues and/or very sluggish deliveries. This option does not,
16247 however, interlock with other processes, so additional queue runners can be
16248 started by other means, or by killing and restarting the daemon.
16250 Setting this option to zero does not suppress queue runs; rather, it disables
16251 the limit, allowing any number of simultaneous queue runner processes to be
16252 run. If you do not want queue runs to occur, omit the &%-q%&&'xx'& setting on
16253 the daemon's command line.
16255 .cindex queues named
16256 .cindex "named queues"
16257 To set limits for different named queues use
16258 an expansion depending on the &$queue_name$& variable.
16260 .option queue_smtp_domains main "domain list&!!" unset
16261 .cindex "queueing incoming messages"
16262 .cindex "message" "queueing remote deliveries"
16263 When this option is set, a delivery process is started whenever a message is
16264 received, routing is performed, and local deliveries take place.
16265 However, if any SMTP deliveries are required for domains that match
16266 &%queue_smtp_domains%&, they are not immediately delivered, but instead the
16267 message waits on the queue for the next queue run. Since routing of the message
16268 has taken place, Exim knows to which remote hosts it must be delivered, and so
16269 when the queue run happens, multiple messages for the same host are delivered
16270 over a single SMTP connection. The &%-odqs%& command line option causes all
16271 SMTP deliveries to be queued in this way, and is equivalent to setting
16272 &%queue_smtp_domains%& to &"*"&. See also &%hold_domains%& and
16276 .option receive_timeout main time 0s
16277 .cindex "timeout" "for non-SMTP input"
16278 This option sets the timeout for accepting a non-SMTP message, that is, the
16279 maximum time that Exim waits when reading a message on the standard input. If
16280 the value is zero, it will wait for ever. This setting is overridden by the
16281 &%-or%& command line option. The timeout for incoming SMTP messages is
16282 controlled by &%smtp_receive_timeout%&.
16284 .option received_header_text main string&!! "see below"
16285 .cindex "customizing" "&'Received:'& header"
16286 .cindex "&'Received:'& header line" "customizing"
16287 This string defines the contents of the &'Received:'& message header that is
16288 added to each message, except for the timestamp, which is automatically added
16289 on at the end (preceded by a semicolon). The string is expanded each time it is
16290 used. If the expansion yields an empty string, no &'Received:'& header line is
16291 added to the message. Otherwise, the string should start with the text
16292 &"Received:"& and conform to the RFC 2822 specification for &'Received:'&
16293 header lines. The default setting is:
16296 received_header_text = Received: \
16297 ${if def:sender_rcvhost {from $sender_rcvhost\n\t}\
16298 {${if def:sender_ident \
16299 {from ${quote_local_part:$sender_ident} }}\
16300 ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\
16301 by $primary_hostname \
16302 ${if def:received_protocol {with $received_protocol}} \
16303 ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\
16304 (Exim $version_number)\n\t\
16305 ${if def:sender_address \
16306 {(envelope-from <$sender_address>)\n\t}}\
16307 id $message_exim_id\
16308 ${if def:received_for {\n\tfor $received_for}}
16311 The reference to the TLS cipher is omitted when Exim is built without TLS
16312 support. The use of conditional expansions ensures that this works for both
16313 locally generated messages and messages received from remote hosts, giving
16314 header lines such as the following:
16316 Received: from scrooge.carol.example ([192.168.12.25] ident=root)
16317 by marley.carol.example with esmtp (Exim 4.00)
16318 (envelope-from <bob@carol.example>)
16319 id 16IOWa-00019l-00
16320 for chas@dickens.example; Tue, 25 Dec 2001 14:43:44 +0000
16321 Received: by scrooge.carol.example with local (Exim 4.00)
16322 id 16IOWW-000083-00; Tue, 25 Dec 2001 14:43:41 +0000
16324 Until the body of the message has been received, the timestamp is the time when
16325 the message started to be received. Once the body has arrived, and all policy
16326 checks have taken place, the timestamp is updated to the time at which the
16327 message was accepted.
16330 .option received_headers_max main integer 30
16331 .cindex "loop" "prevention"
16332 .cindex "mail loop prevention"
16333 .cindex "&'Received:'& header line" "counting"
16334 When a message is to be delivered, the number of &'Received:'& headers is
16335 counted, and if it is greater than this parameter, a mail loop is assumed to
16336 have occurred, the delivery is abandoned, and an error message is generated.
16337 This applies to both local and remote deliveries.
16340 .option recipient_unqualified_hosts main "host list&!!" unset
16341 .cindex "unqualified addresses"
16342 .cindex "host" "unqualified addresses from"
16343 This option lists those hosts from which Exim is prepared to accept unqualified
16344 recipient addresses in message envelopes. The addresses are made fully
16345 qualified by the addition of the &%qualify_recipient%& value. This option also
16346 affects message header lines. Exim does not reject unqualified recipient
16347 addresses in headers, but it qualifies them only if the message came from a
16348 host that matches &%recipient_unqualified_hosts%&,
16349 or if the message was submitted locally (not using TCP/IP), and the &%-bnq%&
16350 option was not set.
16353 .option recipients_max main integer 0
16354 .cindex "limit" "number of recipients"
16355 .cindex "recipient" "maximum number"
16356 If this option is set greater than zero, it specifies the maximum number of
16357 original recipients for any message. Additional recipients that are generated
16358 by aliasing or forwarding do not count. SMTP messages get a 452 response for
16359 all recipients over the limit; earlier recipients are delivered as normal.
16360 Non-SMTP messages with too many recipients are failed, and no deliveries are
16363 .cindex "RCPT" "maximum number of incoming"
16364 &*Note*&: The RFCs specify that an SMTP server should accept at least 100
16365 RCPT commands in a single message.
16368 .option recipients_max_reject main boolean false
16369 If this option is set true, Exim rejects SMTP messages containing too many
16370 recipients by giving 552 errors to the surplus RCPT commands, and a 554
16371 error to the eventual DATA command. Otherwise (the default) it gives a 452
16372 error to the surplus RCPT commands and accepts the message on behalf of the
16373 initial set of recipients. The remote server should then re-send the message
16374 for the remaining recipients at a later time.
16377 .option remote_max_parallel main integer 2
16378 .cindex "delivery" "parallelism for remote"
16379 This option controls parallel delivery of one message to a number of remote
16380 hosts. If the value is less than 2, parallel delivery is disabled, and Exim
16381 does all the remote deliveries for a message one by one. Otherwise, if a single
16382 message has to be delivered to more than one remote host, or if several copies
16383 have to be sent to the same remote host, up to &%remote_max_parallel%&
16384 deliveries are done simultaneously. If more than &%remote_max_parallel%&
16385 deliveries are required, the maximum number of processes are started, and as
16386 each one finishes, another is begun. The order of starting processes is the
16387 same as if sequential delivery were being done, and can be controlled by the
16388 &%remote_sort_domains%& option. If parallel delivery takes place while running
16389 with debugging turned on, the debugging output from each delivery process is
16390 tagged with its process id.
16392 This option controls only the maximum number of parallel deliveries for one
16393 message in one Exim delivery process. Because Exim has no central queue
16394 manager, there is no way of controlling the total number of simultaneous
16395 deliveries if the configuration allows a delivery attempt as soon as a message
16398 .cindex "number of deliveries"
16399 .cindex "delivery" "maximum number of"
16400 If you want to control the total number of deliveries on the system, you
16401 need to set the &%queue_only%& option. This ensures that all incoming messages
16402 are added to the queue without starting a delivery process. Then set up an Exim
16403 daemon to start queue runner processes at appropriate intervals (probably
16404 fairly often, for example, every minute), and limit the total number of queue
16405 runners by setting the &%queue_run_max%& parameter. Because each queue runner
16406 delivers only one message at a time, the maximum number of deliveries that can
16407 then take place at once is &%queue_run_max%& multiplied by
16408 &%remote_max_parallel%&.
16410 If it is purely remote deliveries you want to control, use
16411 &%queue_smtp_domains%& instead of &%queue_only%&. This has the added benefit of
16412 doing the SMTP routing before queueing, so that several messages for the same
16413 host will eventually get delivered down the same connection.
16416 .option remote_sort_domains main "domain list&!!" unset
16417 .cindex "sorting remote deliveries"
16418 .cindex "delivery" "sorting remote"
16419 When there are a number of remote deliveries for a message, they are sorted by
16420 domain into the order given by this list. For example,
16422 remote_sort_domains = *.cam.ac.uk:*.uk
16424 would attempt to deliver to all addresses in the &'cam.ac.uk'& domain first,
16425 then to those in the &%uk%& domain, then to any others.
16428 .option retry_data_expire main time 7d
16429 .cindex "hints database" "data expiry"
16430 This option sets a &"use before"& time on retry information in Exim's hints
16431 database. Any older retry data is ignored. This means that, for example, once a
16432 host has not been tried for 7 days, Exim behaves as if it has no knowledge of
16436 .option retry_interval_max main time 24h
16437 .cindex "retry" "limit on interval"
16438 .cindex "limit" "on retry interval"
16439 Chapter &<<CHAPretry>>& describes Exim's mechanisms for controlling the
16440 intervals between delivery attempts for messages that cannot be delivered
16441 straight away. This option sets an overall limit to the length of time between
16442 retries. It cannot be set greater than 24 hours; any attempt to do so forces
16446 .option return_path_remove main boolean true
16447 .cindex "&'Return-path:'& header line" "removing"
16448 RFC 2821, section 4.4, states that an SMTP server must insert a
16449 &'Return-path:'& header line into a message when it makes a &"final delivery"&.
16450 The &'Return-path:'& header preserves the sender address as received in the
16451 MAIL command. This description implies that this header should not be present
16452 in an incoming message. If &%return_path_remove%& is true, any existing
16453 &'Return-path:'& headers are removed from messages at the time they are
16454 received. Exim's transports have options for adding &'Return-path:'& headers at
16455 the time of delivery. They are normally used only for final local deliveries.
16458 .option return_size_limit main integer 100K
16459 This option is an obsolete synonym for &%bounce_return_size_limit%&.
16462 .option rfc1413_hosts main "host list&!!" @[]
16464 .cindex "host" "for RFC 1413 calls"
16465 RFC 1413 identification calls are made to any client host which matches
16466 an item in the list.
16467 The default value specifies just this host, being any local interface
16470 .option rfc1413_query_timeout main time 0s
16471 .cindex "RFC 1413" "query timeout"
16472 .cindex "timeout" "for RFC 1413 call"
16473 This sets the timeout on RFC 1413 identification calls. If it is set to zero,
16474 no RFC 1413 calls are ever made.
16477 .option sender_unqualified_hosts main "host list&!!" unset
16478 .cindex "unqualified addresses"
16479 .cindex "host" "unqualified addresses from"
16480 This option lists those hosts from which Exim is prepared to accept unqualified
16481 sender addresses. The addresses are made fully qualified by the addition of
16482 &%qualify_domain%&. This option also affects message header lines. Exim does
16483 not reject unqualified addresses in headers that contain sender addresses, but
16484 it qualifies them only if the message came from a host that matches
16485 &%sender_unqualified_hosts%&, or if the message was submitted locally (not
16486 using TCP/IP), and the &%-bnq%& option was not set.
16488 .option set_environment main "string list" empty
16489 .cindex "environment"
16490 This option allows to set individual environment variables that the
16491 currently linked libraries and programs in child processes use. The
16492 default list is empty,
16495 .option slow_lookup_log main integer 0
16496 .cindex "logging" "slow lookups"
16497 .cindex "dns" "logging slow lookups"
16498 This option controls logging of slow lookups.
16499 If the value is nonzero it is taken as a number of milliseconds
16500 and lookups taking longer than this are logged.
16501 Currently this applies only to DNS lookups.
16505 .option smtp_accept_keepalive main boolean true
16506 .cindex "keepalive" "on incoming connection"
16507 This option controls the setting of the SO_KEEPALIVE option on incoming
16508 TCP/IP socket connections. When set, it causes the kernel to probe idle
16509 connections periodically, by sending packets with &"old"& sequence numbers. The
16510 other end of the connection should send an acknowledgment if the connection is
16511 still okay or a reset if the connection has been aborted. The reason for doing
16512 this is that it has the beneficial effect of freeing up certain types of
16513 connection that can get stuck when the remote host is disconnected without
16514 tidying up the TCP/IP call properly. The keepalive mechanism takes several
16515 hours to detect unreachable hosts.
16519 .option smtp_accept_max main integer 20
16520 .cindex "limit" "incoming SMTP connections"
16521 .cindex "SMTP" "incoming connection count"
16523 This option specifies the maximum number of simultaneous incoming SMTP calls
16524 that Exim will accept. It applies only to the listening daemon; there is no
16525 control (in Exim) when incoming SMTP is being handled by &'inetd'&. If the
16526 value is set to zero, no limit is applied. However, it is required to be
16527 non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is
16528 set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&.
16530 A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit
16531 has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If
16532 that limit has not been reached for the client host, &%smtp_accept_reserve%&
16533 and &%smtp_load_reserve%& are then checked before accepting the connection.
16536 .option smtp_accept_max_nonmail main integer 10
16537 .cindex "limit" "non-mail SMTP commands"
16538 .cindex "SMTP" "limiting non-mail commands"
16539 Exim counts the number of &"non-mail"& commands in an SMTP session, and drops
16540 the connection if there are too many. This option defines &"too many"&. The
16541 check catches some denial-of-service attacks, repeated failing AUTHs, or a mad
16542 client looping sending EHLO, for example. The check is applied only if the
16543 client host matches &%smtp_accept_max_nonmail_hosts%&.
16545 When a new message is expected, one occurrence of RSET is not counted. This
16546 allows a client to send one RSET between messages (this is not necessary,
16547 but some clients do it). Exim also allows one uncounted occurrence of HELO
16548 or EHLO, and one occurrence of STARTTLS between messages. After
16549 starting up a TLS session, another EHLO is expected, and so it too is not
16550 counted. The first occurrence of AUTH in a connection, or immediately
16551 following STARTTLS is not counted. Otherwise, all commands other than
16552 MAIL, RCPT, DATA, and QUIT are counted.
16555 .option smtp_accept_max_nonmail_hosts main "host list&!!" *
16556 You can control which hosts are subject to the &%smtp_accept_max_nonmail%&
16557 check by setting this option. The default value makes it apply to all hosts. By
16558 changing the value, you can exclude any badly-behaved hosts that you have to
16562 . Allow this long option name to split; give it unsplit as a fifth argument
16563 . for the automatic .oindex that is generated by .option.
16564 . We insert " &~&~" which is both pretty nasty visually and results in
16565 . non-searchable text. HowItWorks.txt mentions an option for inserting
16566 . zero-width-space, which would be nicer visually and results in (at least)
16567 . html that Firefox will split on when it's forced to reflow (rather than
16568 . inserting a horizontal scrollbar). However, the text is still not
16569 . searchable. NM changed this occurrence for bug 1197 to no longer allow
16570 . the option name to split.
16572 .option "smtp_accept_max_per_connection" main integer 1000 &&&
16573 smtp_accept_max_per_connection
16574 .cindex "SMTP" "limiting incoming message count"
16575 .cindex "limit" "messages per SMTP connection"
16576 The value of this option limits the number of MAIL commands that Exim is
16577 prepared to accept over a single SMTP connection, whether or not each command
16578 results in the transfer of a message. After the limit is reached, a 421
16579 response is given to subsequent MAIL commands. This limit is a safety
16580 precaution against a client that goes mad (incidents of this type have been
16584 .option smtp_accept_max_per_host main string&!! unset
16585 .cindex "limit" "SMTP connections from one host"
16586 .cindex "host" "limiting SMTP connections from"
16587 This option restricts the number of simultaneous IP connections from a single
16588 host (strictly, from a single IP address) to the Exim daemon. The option is
16589 expanded, to enable different limits to be applied to different hosts by
16590 reference to &$sender_host_address$&. Once the limit is reached, additional
16591 connection attempts from the same host are rejected with error code 421. This
16592 is entirely independent of &%smtp_accept_reserve%&. The option's default value
16593 of zero imposes no limit. If this option is set greater than zero, it is
16594 required that &%smtp_accept_max%& be non-zero.
16596 &*Warning*&: When setting this option you should not use any expansion
16597 constructions that take an appreciable amount of time. The expansion and test
16598 happen in the main daemon loop, in order to reject additional connections
16599 without forking additional processes (otherwise a denial-of-service attack
16600 could cause a vast number or processes to be created). While the daemon is
16601 doing this processing, it cannot accept any other incoming connections.
16605 .option smtp_accept_queue main integer 0
16606 .cindex "SMTP" "incoming connection count"
16607 .cindex "queueing incoming messages"
16608 .cindex "message" "queueing by SMTP connection count"
16609 If the number of simultaneous incoming SMTP connections being handled via the
16610 listening daemon exceeds this value, messages received by SMTP are just placed
16611 on the queue; no delivery processes are started automatically. The count is
16612 fixed at the start of an SMTP connection. It cannot be updated in the
16613 subprocess that receives messages, and so the queueing or not queueing applies
16614 to all messages received in the same connection.
16616 A value of zero implies no limit, and clearly any non-zero value is useful only
16617 if it is less than the &%smtp_accept_max%& value (unless that is zero). See
16618 also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the
16619 various &%-od%&&'x'& command line options.
16622 . See the comment on smtp_accept_max_per_connection
16624 .option "smtp_accept_queue_per_connection" main integer 10 &&&
16625 smtp_accept_queue_per_connection
16626 .cindex "queueing incoming messages"
16627 .cindex "message" "queueing by message count"
16628 This option limits the number of delivery processes that Exim starts
16629 automatically when receiving messages via SMTP, whether via the daemon or by
16630 the use of &%-bs%& or &%-bS%&. If the value of the option is greater than zero,
16631 and the number of messages received in a single SMTP session exceeds this
16632 number, subsequent messages are placed on the queue, but no delivery processes
16633 are started. This helps to limit the number of Exim processes when a server
16634 restarts after downtime and there is a lot of mail waiting for it on other
16635 systems. On large systems, the default should probably be increased, and on
16636 dial-in client systems it should probably be set to zero (that is, disabled).
16639 .option smtp_accept_reserve main integer 0
16640 .cindex "SMTP" "incoming call count"
16641 .cindex "host" "reserved"
16642 When &%smtp_accept_max%& is set greater than zero, this option specifies a
16643 number of SMTP connections that are reserved for connections from the hosts
16644 that are specified in &%smtp_reserve_hosts%&. The value set in
16645 &%smtp_accept_max%& includes this reserve pool. The specified hosts are not
16646 restricted to this number of connections; the option specifies a minimum number
16647 of connection slots for them, not a maximum. It is a guarantee that this group
16648 of hosts can always get at least &%smtp_accept_reserve%& connections. However,
16649 the limit specified by &%smtp_accept_max_per_host%& is still applied to each
16652 For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is
16653 set to 5, once there are 45 active connections (from any hosts), new
16654 connections are accepted only from hosts listed in &%smtp_reserve_hosts%&,
16655 provided the other criteria for acceptance are met.
16658 .option smtp_active_hostname main string&!! unset
16659 .cindex "host" "name in SMTP responses"
16660 .cindex "SMTP" "host name in responses"
16661 .vindex "&$primary_hostname$&"
16662 This option is provided for multi-homed servers that want to masquerade as
16663 several different hosts. At the start of an incoming SMTP connection, its value
16664 is expanded and used instead of the value of &$primary_hostname$& in SMTP
16665 responses. For example, it is used as domain name in the response to an
16666 incoming HELO or EHLO command.
16668 .vindex "&$smtp_active_hostname$&"
16669 The active hostname is placed in the &$smtp_active_hostname$& variable, which
16670 is saved with any messages that are received. It is therefore available for use
16671 in routers and transports when the message is later delivered.
16673 If this option is unset, or if its expansion is forced to fail, or if the
16674 expansion results in an empty string, the value of &$primary_hostname$& is
16675 used. Other expansion failures cause a message to be written to the main and
16676 panic logs, and the SMTP command receives a temporary error. Typically, the
16677 value of &%smtp_active_hostname%& depends on the incoming interface address.
16680 smtp_active_hostname = ${if eq{$received_ip_address}{10.0.0.1}\
16681 {cox.mydomain}{box.mydomain}}
16684 Although &$smtp_active_hostname$& is primarily concerned with incoming
16685 messages, it is also used as the default for HELO commands in callout
16686 verification if there is no remote transport from which to obtain a
16687 &%helo_data%& value.
16689 .option smtp_banner main string&!! "see below"
16690 .cindex "SMTP" "welcome banner"
16691 .cindex "banner for SMTP"
16692 .cindex "welcome banner for SMTP"
16693 .cindex "customizing" "SMTP banner"
16694 This string, which is expanded every time it is used, is output as the initial
16695 positive response to an SMTP connection. The default setting is:
16697 smtp_banner = $smtp_active_hostname ESMTP Exim \
16698 $version_number $tod_full
16700 Failure to expand the string causes a panic error. If you want to create a
16701 multiline response to the initial SMTP connection, use &"\n"& in the string at
16702 appropriate points, but not at the end. Note that the 220 code is not included
16703 in this string. Exim adds it automatically (several times in the case of a
16704 multiline response).
16707 .option smtp_check_spool_space main boolean true
16708 .cindex "checking disk space"
16709 .cindex "disk space, checking"
16710 .cindex "spool directory" "checking space"
16711 When this option is set, if an incoming SMTP session encounters the SIZE
16712 option on a MAIL command, it checks that there is enough space in the
16713 spool directory's partition to accept a message of that size, while still
16714 leaving free the amount specified by &%check_spool_space%& (even if that value
16715 is zero). If there isn't enough space, a temporary error code is returned.
16718 .option smtp_connect_backlog main integer 20
16719 .cindex "connection backlog"
16720 .cindex "SMTP" "connection backlog"
16721 .cindex "backlog of connections"
16722 This option specifies a maximum number of waiting SMTP connections. Exim passes
16723 this value to the TCP/IP system when it sets up its listener. Once this number
16724 of connections are waiting for the daemon's attention, subsequent connection
16725 attempts are refused at the TCP/IP level. At least, that is what the manuals
16726 say; in some circumstances such connection attempts have been observed to time
16727 out instead. For large systems it is probably a good idea to increase the
16728 value (to 50, say). It also gives some protection against denial-of-service
16729 attacks by SYN flooding.
16732 .option smtp_enforce_sync main boolean true
16733 .cindex "SMTP" "synchronization checking"
16734 .cindex "synchronization checking in SMTP"
16735 The SMTP protocol specification requires the client to wait for a response from
16736 the server at certain points in the dialogue. Without PIPELINING these
16737 synchronization points are after every command; with PIPELINING they are
16738 fewer, but they still exist.
16740 Some spamming sites send out a complete set of SMTP commands without waiting
16741 for any response. Exim protects against this by rejecting a message if the
16742 client has sent further input when it should not have. The error response &"554
16743 SMTP synchronization error"& is sent, and the connection is dropped. Testing
16744 for this error cannot be perfect because of transmission delays (unexpected
16745 input may be on its way but not yet received when Exim checks). However, it
16746 does detect many instances.
16748 The check can be globally disabled by setting &%smtp_enforce_sync%& false.
16749 If you want to disable the check selectively (for example, only for certain
16750 hosts), you can do so by an appropriate use of a &%control%& modifier in an ACL
16751 (see section &<<SECTcontrols>>&). See also &%pipelining_advertise_hosts%&.
16755 .option smtp_etrn_command main string&!! unset
16756 .cindex "ETRN" "command to be run"
16757 .vindex "&$domain$&"
16758 If this option is set, the given command is run whenever an SMTP ETRN
16759 command is received from a host that is permitted to issue such commands (see
16760 chapter &<<CHAPACL>>&). The string is split up into separate arguments which
16761 are independently expanded. The expansion variable &$domain$& is set to the
16762 argument of the ETRN command, and no syntax checking is done on it. For
16765 smtp_etrn_command = /etc/etrn_command $domain \
16766 $sender_host_address
16768 A new process is created to run the command, but Exim does not wait for it to
16769 complete. Consequently, its status cannot be checked. If the command cannot be
16770 run, a line is written to the panic log, but the ETRN caller still receives
16771 a 250 success response. Exim is normally running under its own uid when
16772 receiving SMTP, so it is not possible for it to change the uid before running
16776 .option smtp_etrn_serialize main boolean true
16777 .cindex "ETRN" "serializing"
16778 When this option is set, it prevents the simultaneous execution of more than
16779 one identical command as a result of ETRN in an SMTP connection. See
16780 section &<<SECTETRN>>& for details.
16783 .option smtp_load_reserve main fixed-point unset
16784 .cindex "load average"
16785 If the system load average ever gets higher than this, incoming SMTP calls are
16786 accepted only from those hosts that match an entry in &%smtp_reserve_hosts%&.
16787 If &%smtp_reserve_hosts%& is not set, no incoming SMTP calls are accepted when
16788 the load is over the limit. The option has no effect on ancient operating
16789 systems on which Exim cannot determine the load average. See also
16790 &%deliver_queue_load_max%& and &%queue_only_load%&.
16794 .option smtp_max_synprot_errors main integer 3
16795 .cindex "SMTP" "limiting syntax and protocol errors"
16796 .cindex "limit" "SMTP syntax and protocol errors"
16797 Exim rejects SMTP commands that contain syntax or protocol errors. In
16798 particular, a syntactically invalid email address, as in this command:
16800 RCPT TO:<abc xyz@a.b.c>
16802 causes immediate rejection of the command, before any other tests are done.
16803 (The ACL cannot be run if there is no valid address to set up for it.) An
16804 example of a protocol error is receiving RCPT before MAIL. If there are
16805 too many syntax or protocol errors in one SMTP session, the connection is
16806 dropped. The limit is set by this option.
16808 .cindex "PIPELINING" "expected errors"
16809 When the PIPELINING extension to SMTP is in use, some protocol errors are
16810 &"expected"&, for instance, a RCPT command after a rejected MAIL command.
16811 Exim assumes that PIPELINING will be used if it advertises it (see
16812 &%pipelining_advertise_hosts%&), and in this situation, &"expected"& errors do
16813 not count towards the limit.
16817 .option smtp_max_unknown_commands main integer 3
16818 .cindex "SMTP" "limiting unknown commands"
16819 .cindex "limit" "unknown SMTP commands"
16820 If there are too many unrecognized commands in an incoming SMTP session, an
16821 Exim server drops the connection. This is a defence against some kinds of abuse
16824 into making connections to SMTP ports; in these circumstances, a number of
16825 non-SMTP command lines are sent first.
16829 .option smtp_ratelimit_hosts main "host list&!!" unset
16830 .cindex "SMTP" "rate limiting"
16831 .cindex "limit" "rate of message arrival"
16832 .cindex "RCPT" "rate limiting"
16833 Some sites find it helpful to be able to limit the rate at which certain hosts
16834 can send them messages, and the rate at which an individual message can specify
16837 Exim has two rate-limiting facilities. This section describes the older
16838 facility, which can limit rates within a single connection. The newer
16839 &%ratelimit%& ACL condition can limit rates across all connections. See section
16840 &<<SECTratelimiting>>& for details of the newer facility.
16842 When a host matches &%smtp_ratelimit_hosts%&, the values of
16843 &%smtp_ratelimit_mail%& and &%smtp_ratelimit_rcpt%& are used to control the
16844 rate of acceptance of MAIL and RCPT commands in a single SMTP session,
16845 respectively. Each option, if set, must contain a set of four comma-separated
16849 A threshold, before which there is no rate limiting.
16851 An initial time delay. Unlike other times in Exim, numbers with decimal
16852 fractional parts are allowed here.
16854 A factor by which to increase the delay each time.
16856 A maximum value for the delay. This should normally be less than 5 minutes,
16857 because after that time, the client is liable to timeout the SMTP command.
16860 For example, these settings have been used successfully at the site which
16861 first suggested this feature, for controlling mail from their customers:
16863 smtp_ratelimit_mail = 2,0.5s,1.05,4m
16864 smtp_ratelimit_rcpt = 4,0.25s,1.015,4m
16866 The first setting specifies delays that are applied to MAIL commands after
16867 two have been received over a single connection. The initial delay is 0.5
16868 seconds, increasing by a factor of 1.05 each time. The second setting applies
16869 delays to RCPT commands when more than four occur in a single message.
16872 .option smtp_ratelimit_mail main string unset
16873 See &%smtp_ratelimit_hosts%& above.
16876 .option smtp_ratelimit_rcpt main string unset
16877 See &%smtp_ratelimit_hosts%& above.
16880 .option smtp_receive_timeout main time&!! 5m
16881 .cindex "timeout" "for SMTP input"
16882 .cindex "SMTP" "input timeout"
16883 This sets a timeout value for SMTP reception. It applies to all forms of SMTP
16884 input, including batch SMTP. If a line of input (either an SMTP command or a
16885 data line) is not received within this time, the SMTP connection is dropped and
16886 the message is abandoned.
16887 A line is written to the log containing one of the following messages:
16889 SMTP command timeout on connection from...
16890 SMTP data timeout on connection from...
16892 The former means that Exim was expecting to read an SMTP command; the latter
16893 means that it was in the DATA phase, reading the contents of a message.
16895 If the first character of the option is a &"$"& the option is
16896 expanded before use and may depend on
16897 &$sender_host_name$&, &$sender_host_address$& and &$sender_host_port$&.
16901 The value set by this option can be overridden by the
16902 &%-os%& command-line option. A setting of zero time disables the timeout, but
16903 this should never be used for SMTP over TCP/IP. (It can be useful in some cases
16904 of local input using &%-bs%& or &%-bS%&.) For non-SMTP input, the reception
16905 timeout is controlled by &%receive_timeout%& and &%-or%&.
16908 .option smtp_reserve_hosts main "host list&!!" unset
16909 This option defines hosts for which SMTP connections are reserved; see
16910 &%smtp_accept_reserve%& and &%smtp_load_reserve%& above.
16913 .option smtp_return_error_details main boolean false
16914 .cindex "SMTP" "details policy failures"
16915 .cindex "policy control" "rejection, returning details"
16916 In the default state, Exim uses bland messages such as
16917 &"Administrative prohibition"& when it rejects SMTP commands for policy
16918 reasons. Many sysadmins like this because it gives away little information
16919 to spammers. However, some other sysadmins who are applying strict checking
16920 policies want to give out much fuller information about failures. Setting
16921 &%smtp_return_error_details%& true causes Exim to be more forthcoming. For
16922 example, instead of &"Administrative prohibition"&, it might give:
16924 550-Rejected after DATA: '>' missing at end of address:
16925 550 failing address in "From" header is: <user@dom.ain
16929 .option smtputf8_advertise_hosts main "host list&!!" *
16930 .cindex "SMTPUTF8" "advertising"
16931 When Exim is built with support for internationalised mail names,
16932 the availability thereof is advertised in
16933 response to EHLO only to those client hosts that match this option. See
16934 chapter &<<CHAPi18n>>& for details of Exim's support for internationalisation.
16937 .option spamd_address main string "127.0.0.1 783"
16938 This option is available when Exim is compiled with the content-scanning
16939 extension. It specifies how Exim connects to SpamAssassin's &%spamd%& daemon.
16940 See section &<<SECTscanspamass>>& for more details.
16944 .option spf_guess main string "v=spf1 a/24 mx/24 ptr ?all"
16945 This option is available when Exim is compiled with SPF support.
16946 See section &<<SECSPF>>& for more details.
16950 .option split_spool_directory main boolean false
16951 .cindex "multiple spool directories"
16952 .cindex "spool directory" "split"
16953 .cindex "directories, multiple"
16954 If this option is set, it causes Exim to split its input directory into 62
16955 subdirectories, each with a single alphanumeric character as its name. The
16956 sixth character of the message id is used to allocate messages to
16957 subdirectories; this is the least significant base-62 digit of the time of
16958 arrival of the message.
16960 Splitting up the spool in this way may provide better performance on systems
16961 where there are long mail queues, by reducing the number of files in any one
16962 directory. The msglog directory is also split up in a similar way to the input
16963 directory; however, if &%preserve_message_logs%& is set, all old msglog files
16964 are still placed in the single directory &_msglog.OLD_&.
16966 It is not necessary to take any special action for existing messages when
16967 changing &%split_spool_directory%&. Exim notices messages that are in the
16968 &"wrong"& place, and continues to process them. If the option is turned off
16969 after a period of being on, the subdirectories will eventually empty and be
16970 automatically deleted.
16972 When &%split_spool_directory%& is set, the behaviour of queue runner processes
16973 changes. Instead of creating a list of all messages in the queue, and then
16974 trying to deliver each one in turn, it constructs a list of those in one
16975 sub-directory and tries to deliver them, before moving on to the next
16976 sub-directory. The sub-directories are processed in a random order. This
16977 spreads out the scanning of the input directories, and uses less memory. It is
16978 particularly beneficial when there are lots of messages on the queue. However,
16979 if &%queue_run_in_order%& is set, none of this new processing happens. The
16980 entire queue has to be scanned and sorted before any deliveries can start.
16983 .option spool_directory main string&!! "set at compile time"
16984 .cindex "spool directory" "path to"
16985 This defines the directory in which Exim keeps its spool, that is, the messages
16986 it is waiting to deliver. The default value is taken from the compile-time
16987 configuration setting, if there is one. If not, this option must be set. The
16988 string is expanded, so it can contain, for example, a reference to
16989 &$primary_hostname$&.
16991 If the spool directory name is fixed on your installation, it is recommended
16992 that you set it at build time rather than from this option, particularly if the
16993 log files are being written to the spool directory (see &%log_file_path%&).
16994 Otherwise log files cannot be used for errors that are detected early on, such
16995 as failures in the configuration file.
16997 By using this option to override the compiled-in path, it is possible to run
16998 tests of Exim without using the standard spool.
17000 .option spool_wireformat main boolean false
17001 .cindex "spool directory" "file formats"
17002 If this option is set, Exim may for some messages use an alternative format
17003 for data-files in the spool which matches the wire format.
17004 Doing this permits more efficient message reception and transmission.
17005 Currently it is only done for messages received using the ESMTP CHUNKING
17008 The following variables will not have useful values:
17010 $max_received_linelength
17015 Users of the local_scan() API (see &<<CHAPlocalscan>>&),
17016 and any external programs which are passed a reference to a message data file
17017 (except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
17018 will need to be aware of the different formats potentially available.
17020 Using any of the ACL conditions noted will negate the reception benefit
17021 (as a Unix-mbox-format file is constructed for them).
17022 The transmission benefit is maintained.
17024 .option sqlite_lock_timeout main time 5s
17025 .cindex "sqlite lookup type" "lock timeout"
17026 This option controls the timeout that the &(sqlite)& lookup uses when trying to
17027 access an SQLite database. See section &<<SECTsqlite>>& for more details.
17029 .option strict_acl_vars main boolean false
17030 .cindex "&ACL;" "variables, handling unset"
17031 This option controls what happens if a syntactically valid but undefined ACL
17032 variable is referenced. If it is false (the default), an empty string
17033 is substituted; if it is true, an error is generated. See section
17034 &<<SECTaclvariables>>& for details of ACL variables.
17036 .option strip_excess_angle_brackets main boolean false
17037 .cindex "angle brackets, excess"
17038 If this option is set, redundant pairs of angle brackets round &"route-addr"&
17039 items in addresses are stripped. For example, &'<<xxx@a.b.c.d>>'& is
17040 treated as &'<xxx@a.b.c.d>'&. If this is in the envelope and the message is
17041 passed on to another MTA, the excess angle brackets are not passed on. If this
17042 option is not set, multiple pairs of angle brackets cause a syntax error.
17045 .option strip_trailing_dot main boolean false
17046 .cindex "trailing dot on domain"
17047 .cindex "dot" "trailing on domain"
17048 If this option is set, a trailing dot at the end of a domain in an address is
17049 ignored. If this is in the envelope and the message is passed on to another
17050 MTA, the dot is not passed on. If this option is not set, a dot at the end of a
17051 domain causes a syntax error.
17052 However, addresses in header lines are checked only when an ACL requests header
17056 .option syslog_duplication main boolean true
17057 .cindex "syslog" "duplicate log lines; suppressing"
17058 When Exim is logging to syslog, it writes the log lines for its three
17059 separate logs at different syslog priorities so that they can in principle
17060 be separated on the logging hosts. Some installations do not require this
17061 separation, and in those cases, the duplication of certain log lines is a
17062 nuisance. If &%syslog_duplication%& is set false, only one copy of any
17063 particular log line is written to syslog. For lines that normally go to
17064 both the main log and the reject log, the reject log version (possibly
17065 containing message header lines) is written, at LOG_NOTICE priority.
17066 Lines that normally go to both the main and the panic log are written at
17067 the LOG_ALERT priority.
17070 .option syslog_facility main string unset
17071 .cindex "syslog" "facility; setting"
17072 This option sets the syslog &"facility"& name, used when Exim is logging to
17073 syslog. The value must be one of the strings &"mail"&, &"user"&, &"news"&,
17074 &"uucp"&, &"daemon"&, or &"local&'x'&"& where &'x'& is a digit between 0 and 7.
17075 If this option is unset, &"mail"& is used. See chapter &<<CHAPlog>>& for
17076 details of Exim's logging.
17079 .option syslog_pid main boolean true
17080 .cindex "syslog" "pid"
17081 If &%syslog_pid%& is set false, the PID on Exim's log lines are
17082 omitted when these lines are sent to syslog. (Syslog normally prefixes
17083 the log lines with the PID of the logging process automatically.) You need
17084 to enable the &`+pid`& log selector item, if you want Exim to write it's PID
17085 into the logs.) See chapter &<<CHAPlog>>& for details of Exim's logging.
17089 .option syslog_processname main string &`exim`&
17090 .cindex "syslog" "process name; setting"
17091 This option sets the syslog &"ident"& name, used when Exim is logging to
17092 syslog. The value must be no longer than 32 characters. See chapter
17093 &<<CHAPlog>>& for details of Exim's logging.
17097 .option syslog_timestamp main boolean true
17098 .cindex "syslog" "timestamps"
17099 If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
17100 omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
17101 details of Exim's logging.
17104 .option system_filter main string&!! unset
17105 .cindex "filter" "system filter"
17106 .cindex "system filter" "specifying"
17107 .cindex "Sieve filter" "not available for system filter"
17108 This option specifies an Exim filter file that is applied to all messages at
17109 the start of each delivery attempt, before any routing is done. System filters
17110 must be Exim filters; they cannot be Sieve filters. If the system filter
17111 generates any deliveries to files or pipes, or any new mail messages, the
17112 appropriate &%system_filter_..._transport%& option(s) must be set, to define
17113 which transports are to be used. Details of this facility are given in chapter
17114 &<<CHAPsystemfilter>>&.
17115 A forced expansion failure results in no filter operation.
17118 .option system_filter_directory_transport main string&!! unset
17119 .vindex "&$address_file$&"
17120 This sets the name of the transport driver that is to be used when the
17121 &%save%& command in a system message filter specifies a path ending in &"/"&,
17122 implying delivery of each message into a separate file in some directory.
17123 During the delivery, the variable &$address_file$& contains the path name.
17126 .option system_filter_file_transport main string&!! unset
17127 .cindex "file" "transport for system filter"
17128 This sets the name of the transport driver that is to be used when the &%save%&
17129 command in a system message filter specifies a path not ending in &"/"&. During
17130 the delivery, the variable &$address_file$& contains the path name.
17132 .option system_filter_group main string unset
17133 .cindex "gid (group id)" "system filter"
17134 This option is used only when &%system_filter_user%& is also set. It sets the
17135 gid under which the system filter is run, overriding any gid that is associated
17136 with the user. The value may be numerical or symbolic.
17138 .option system_filter_pipe_transport main string&!! unset
17139 .cindex "&(pipe)& transport" "for system filter"
17140 .vindex "&$address_pipe$&"
17141 This specifies the transport driver that is to be used when a &%pipe%& command
17142 is used in a system filter. During the delivery, the variable &$address_pipe$&
17143 contains the pipe command.
17146 .option system_filter_reply_transport main string&!! unset
17147 .cindex "&(autoreply)& transport" "for system filter"
17148 This specifies the transport driver that is to be used when a &%mail%& command
17149 is used in a system filter.
17152 .option system_filter_user main string unset
17153 .cindex "uid (user id)" "system filter"
17154 If this option is set to root, the system filter is run in the main Exim
17155 delivery process, as root. Otherwise, the system filter runs in a separate
17156 process, as the given user, defaulting to the Exim run-time user.
17157 Unless the string consists entirely of digits, it
17158 is looked up in the password data. Failure to find the named user causes a
17159 configuration error. The gid is either taken from the password data, or
17160 specified by &%system_filter_group%&. When the uid is specified numerically,
17161 &%system_filter_group%& is required to be set.
17163 If the system filter generates any pipe, file, or reply deliveries, the uid
17164 under which the filter is run is used when transporting them, unless a
17165 transport option overrides.
17168 .option tcp_nodelay main boolean true
17169 .cindex "daemon" "TCP_NODELAY on sockets"
17170 .cindex "Nagle algorithm"
17171 .cindex "TCP_NODELAY on listening sockets"
17172 If this option is set false, it stops the Exim daemon setting the
17173 TCP_NODELAY option on its listening sockets. Setting TCP_NODELAY
17174 turns off the &"Nagle algorithm"&, which is a way of improving network
17175 performance in interactive (character-by-character) situations. Turning it off
17176 should improve Exim's performance a bit, so that is what happens by default.
17177 However, it appears that some broken clients cannot cope, and time out. Hence
17178 this option. It affects only those sockets that are set up for listening by the
17179 daemon. Sockets created by the smtp transport for delivering mail always set
17183 .option timeout_frozen_after main time 0s
17184 .cindex "frozen messages" "timing out"
17185 .cindex "timeout" "frozen messages"
17186 If &%timeout_frozen_after%& is set to a time greater than zero, a frozen
17187 message of any kind that has been on the queue for longer than the given time
17188 is automatically cancelled at the next queue run. If the frozen message is a
17189 bounce message, it is just discarded; otherwise, a bounce is sent to the
17190 sender, in a similar manner to cancellation by the &%-Mg%& command line option.
17191 If you want to timeout frozen bounce messages earlier than other kinds of
17192 frozen message, see &%ignore_bounce_errors_after%&.
17194 &*Note:*& the default value of zero means no timeouts; with this setting,
17195 frozen messages remain on the queue forever (except for any frozen bounce
17196 messages that are released by &%ignore_bounce_errors_after%&).
17199 .option timezone main string unset
17200 .cindex "timezone, setting"
17201 .cindex "environment" "values from"
17202 The value of &%timezone%& is used to set the environment variable TZ while
17203 running Exim (if it is different on entry). This ensures that all timestamps
17204 created by Exim are in the required timezone. If you want all your timestamps
17205 to be in UTC (aka GMT) you should set
17209 The default value is taken from TIMEZONE_DEFAULT in &_Local/Makefile_&,
17210 or, if that is not set, from the value of the TZ environment variable when Exim
17211 is built. If &%timezone%& is set to the empty string, either at build or run
17212 time, any existing TZ variable is removed from the environment when Exim
17213 runs. This is appropriate behaviour for obtaining wall-clock time on some, but
17214 unfortunately not all, operating systems.
17217 .option tls_advertise_hosts main "host list&!!" *
17218 .cindex "TLS" "advertising"
17219 .cindex "encryption" "on SMTP connection"
17220 .cindex "SMTP" "encrypted connection"
17221 When Exim is built with support for TLS encrypted connections, the availability
17222 of the STARTTLS command to set up an encrypted session is advertised in
17223 response to EHLO only to those client hosts that match this option. See
17224 chapter &<<CHAPTLS>>& for details of Exim's support for TLS.
17225 Note that the default value requires that a certificate be supplied
17226 using the &%tls_certificate%& option. If TLS support for incoming connections
17227 is not required the &%tls_advertise_hosts%& option should be set empty.
17230 .option tls_certificate main string list&!! unset
17231 .cindex "TLS" "server certificate; location of"
17232 .cindex "certificate" "server, location of"
17233 The value of this option is expanded, and must then be a list of absolute paths to
17234 files which contains the server's certificates. Commonly only one file is
17236 The server's private key is also
17237 assumed to be in this file if &%tls_privatekey%& is unset. See chapter
17238 &<<CHAPTLS>>& for further details.
17240 &*Note*&: The certificates defined by this option are used only when Exim is
17241 receiving incoming messages as a server. If you want to supply certificates for
17242 use when sending messages as a client, you must set the &%tls_certificate%&
17243 option in the relevant &(smtp)& transport.
17245 &*Note*&: If you use filenames based on IP addresses, change the list
17246 separator in the usual way to avoid confusion under IPv6.
17248 &*Note*&: Under versions of OpenSSL preceding 1.1.1,
17249 when a list of more than one
17250 file is used, the &$tls_in_ourcert$& variable is unreliable.
17252 &*Note*&: OCSP stapling is not usable under OpenSSL
17253 when a list of more than one file is used.
17255 If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
17256 if the OpenSSL build supports TLS extensions and the TLS client sends the
17257 Server Name Indication extension, then this option and others documented in
17258 &<<SECTtlssni>>& will be re-expanded.
17260 If this option is unset or empty a fresh self-signed certificate will be
17261 generated for every connection.
17263 .option tls_crl main string&!! unset
17264 .cindex "TLS" "server certificate revocation list"
17265 .cindex "certificate" "revocation list for server"
17266 This option specifies a certificate revocation list. The expanded value must
17267 be the name of a file that contains CRLs in PEM format.
17269 Under OpenSSL the option can specify a directory with CRL files.
17271 &*Note:*& Under OpenSSL the option must, if given, supply a CRL
17272 for each signing element of the certificate chain (i.e. all but the leaf).
17273 For the file variant this can be multiple PEM blocks in the one file.
17275 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17278 .option tls_dh_max_bits main integer 2236
17279 .cindex "TLS" "D-H bit count"
17280 The number of bits used for Diffie-Hellman key-exchange may be suggested by
17281 the chosen TLS library. That value might prove to be too high for
17282 interoperability. This option provides a maximum clamp on the value
17283 suggested, trading off security for interoperability.
17285 The value must be at least 1024.
17287 The value 2236 was chosen because, at time of adding the option, it was the
17288 hard-coded maximum value supported by the NSS cryptographic library, as used
17289 by Thunderbird, while GnuTLS was suggesting 2432 bits as normal.
17291 If you prefer more security and are willing to break some clients, raise this
17294 Note that the value passed to GnuTLS for *generating* a new prime may be a
17295 little less than this figure, because GnuTLS is inexact and may produce a
17296 larger prime than requested.
17299 .option tls_dhparam main string&!! unset
17300 .cindex "TLS" "D-H parameters for server"
17301 The value of this option is expanded and indicates the source of DH parameters
17302 to be used by Exim.
17304 &*Note: The Exim Maintainers strongly recommend using a filename with site-generated
17305 local DH parameters*&, which has been supported across all versions of Exim. The
17306 other specific constants available are a fallback so that even when
17307 "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS.
17309 If &%tls_dhparam%& is a filename starting with a &`/`&,
17310 then it names a file from which DH
17311 parameters should be loaded. If the file exists, it should hold a PEM-encoded
17312 PKCS#3 representation of the DH prime. If the file does not exist, for
17313 OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and
17314 fill it with a generated DH prime. For OpenSSL, if the DH bit-count from
17315 loading the file is greater than &%tls_dh_max_bits%& then it will be ignored,
17316 and treated as though the &%tls_dhparam%& were set to "none".
17318 If this option expands to the string "none", then no DH parameters will be
17321 If this option expands to the string "historic" and Exim is using GnuTLS, then
17322 Exim will attempt to load a file from inside the spool directory. If the file
17323 does not exist, Exim will attempt to create it.
17324 See section &<<SECTgnutlsparam>>& for further details.
17326 If Exim is using OpenSSL and this option is empty or unset, then Exim will load
17327 a default DH prime; the default is Exim-specific but lacks verifiable provenance.
17329 In older versions of Exim the default was the 2048 bit prime described in section
17330 2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which
17331 in IKE is assigned number 23.
17333 Otherwise, the option must expand to the name used by Exim for any of a number
17334 of DH primes specified in RFC 2409, RFC 3526, RFC 5114, RFC 7919, or from other
17335 sources. As names, Exim uses a standard specified name, else "ike" followed by
17336 the number used by IKE, or "default" which corresponds to
17337 &`exim.dev.20160529.3`&.
17339 The available standard primes are:
17340 &`ffdhe2048`&, &`ffdhe3072`&, &`ffdhe4096`&, &`ffdhe6144`&, &`ffdhe8192`&,
17341 &`ike1`&, &`ike2`&, &`ike5`&,
17342 &`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&,
17343 &`ike22`&, &`ike23`& and &`ike24`&.
17345 The available additional primes are:
17346 &`exim.dev.20160529.1`&, &`exim.dev.20160529.2`& and &`exim.dev.20160529.3`&.
17348 Some of these will be too small to be accepted by clients.
17349 Some may be too large to be accepted by clients.
17350 The open cryptographic community has suspicions about the integrity of some
17351 of the later IKE values, which led into RFC7919 providing new fixed constants
17352 (the "ffdhe" identifiers).
17354 At this point, all of the "ike" values should be considered obsolete;
17355 they're still in Exim to avoid breaking unusual configurations, but are
17356 candidates for removal the next time we have backwards-incompatible changes.
17358 The TLS protocol does not negotiate an acceptable size for this; clients tend
17359 to hard-drop connections if what is offered by the server is unacceptable,
17360 whether too large or too small, and there's no provision for the client to
17361 tell the server what these constraints are. Thus, as a server operator, you
17362 need to make an educated guess as to what is most likely to work for your
17365 Some known size constraints suggest that a bit-size in the range 2048 to 2236
17366 is most likely to maximise interoperability. The upper bound comes from
17367 applications using the Mozilla Network Security Services (NSS) library, which
17368 used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many
17369 mail user agents (MUAs). The lower bound comes from Debian installs of Exim4
17370 prior to the 4.80 release, as Debian used to patch Exim to raise the minimum
17371 acceptable bound from 1024 to 2048.
17374 .option tls_eccurve main string&!! &`auto`&
17375 .cindex TLS "EC cryptography"
17376 This option selects a EC curve for use by Exim when used with OpenSSL.
17377 It has no effect when Exim is used with GnuTLS.
17379 After expansion it must contain a valid EC curve parameter, such as
17380 &`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual
17381 for valid selections.
17383 For OpenSSL versions before (and not including) 1.0.2, the string
17384 &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions
17385 &`auto`& tells the library to choose.
17387 If the option expands to an empty string, no EC curves will be enabled.
17390 .option tls_ocsp_file main string&!! unset
17391 .cindex TLS "certificate status"
17392 .cindex TLS "OCSP proof file"
17394 must if set expand to the absolute path to a file which contains a current
17395 status proof for the server's certificate, as obtained from the
17396 Certificate Authority.
17398 Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
17400 For GnuTLS 3.5.6 or later the expanded value of this option can be a list
17401 of files, to match a list given for the &%tls_certificate%& option.
17402 The ordering of the two lists must match.
17405 .option tls_on_connect_ports main "string list" unset
17408 This option specifies a list of incoming SSMTP (aka SMTPS) ports that should
17409 operate the SSMTP (SMTPS) protocol, where a TLS session is immediately
17410 set up without waiting for the client to issue a STARTTLS command. For
17411 further details, see section &<<SECTsupobssmt>>&.
17415 .option tls_privatekey main string list&!! unset
17416 .cindex "TLS" "server private key; location of"
17417 The value of this option is expanded, and must then be a list of absolute paths to
17418 files which contains the server's private keys.
17419 If this option is unset, or if
17420 the expansion is forced to fail, or the result is an empty string, the private
17421 key is assumed to be in the same file as the server's certificates. See chapter
17422 &<<CHAPTLS>>& for further details.
17424 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17427 .option tls_remember_esmtp main boolean false
17428 .cindex "TLS" "esmtp state; remembering"
17429 .cindex "TLS" "broken clients"
17430 If this option is set true, Exim violates the RFCs by remembering that it is in
17431 &"esmtp"& state after successfully negotiating a TLS session. This provides
17432 support for broken clients that fail to send a new EHLO after starting a
17436 .option tls_require_ciphers main string&!! unset
17437 .cindex "TLS" "requiring specific ciphers"
17438 .cindex "cipher" "requiring specific"
17439 This option controls which ciphers can be used for incoming TLS connections.
17440 The &(smtp)& transport has an option of the same name for controlling outgoing
17441 connections. This option is expanded for each connection, so can be varied for
17442 different clients if required. The value of this option must be a list of
17443 permitted cipher suites. The OpenSSL and GnuTLS libraries handle cipher control
17444 in somewhat different ways. If GnuTLS is being used, the client controls the
17445 preference order of the available ciphers. Details are given in sections
17446 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
17449 .option tls_try_verify_hosts main "host list&!!" unset
17450 .cindex "TLS" "client certificate verification"
17451 .cindex "certificate" "verification of client"
17452 See &%tls_verify_hosts%& below.
17455 .option tls_verify_certificates main string&!! system
17456 .cindex "TLS" "client certificate verification"
17457 .cindex "certificate" "verification of client"
17458 The value of this option is expanded, and must then be either the
17460 or the absolute path to
17461 a file or directory containing permitted certificates for clients that
17462 match &%tls_verify_hosts%& or &%tls_try_verify_hosts%&.
17464 The "system" value for the option will use a
17465 system default location compiled into the SSL library.
17466 This is not available for GnuTLS versions preceding 3.0.20,
17467 and will be taken as empty; an explicit location
17470 The use of a directory for the option value is not available for GnuTLS versions
17471 preceding 3.3.6 and a single file must be used.
17473 With OpenSSL the certificates specified
17475 either by file or directory
17476 are added to those given by the system default location.
17478 These certificates should be for the certificate authorities trusted, rather
17479 than the public cert of individual clients. With both OpenSSL and GnuTLS, if
17480 the value is a file then the certificates are sent by Exim as a server to
17481 connecting clients, defining the list of accepted certificate authorities.
17482 Thus the values defined should be considered public data. To avoid this,
17483 use the explicit directory version.
17485 See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
17487 A forced expansion failure or setting to an empty string is equivalent to
17491 .option tls_verify_hosts main "host list&!!" unset
17492 .cindex "TLS" "client certificate verification"
17493 .cindex "certificate" "verification of client"
17494 This option, along with &%tls_try_verify_hosts%&, controls the checking of
17495 certificates from clients. The expected certificates are defined by
17496 &%tls_verify_certificates%&, which must be set. A configuration error occurs if
17497 either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and
17498 &%tls_verify_certificates%& is not set.
17500 Any client that matches &%tls_verify_hosts%& is constrained by
17501 &%tls_verify_certificates%&. When the client initiates a TLS session, it must
17502 present one of the listed certificates. If it does not, the connection is
17503 aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require
17504 the host to use TLS. It can still send SMTP commands through unencrypted
17505 connections. Forcing a client to use TLS has to be done separately using an
17506 ACL to reject inappropriate commands when the connection is not encrypted.
17508 A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client
17509 matches this option (but not &%tls_verify_hosts%&), Exim requests a
17510 certificate and checks it against &%tls_verify_certificates%&, but does not
17511 abort the connection if there is no certificate or if it does not match. This
17512 state can be detected in an ACL, which makes it possible to implement policies
17513 such as &"accept for relay only if a verified certificate has been received,
17514 but accept for local delivery if encrypted, even without a verified
17517 Client hosts that match neither of these lists are not asked to present
17521 .option trusted_groups main "string list&!!" unset
17522 .cindex "trusted groups"
17523 .cindex "groups" "trusted"
17524 This option is expanded just once, at the start of Exim's processing. If this
17525 option is set, any process that is running in one of the listed groups, or
17526 which has one of them as a supplementary group, is trusted. The groups can be
17527 specified numerically or by name. See section &<<SECTtrustedadmin>>& for
17528 details of what trusted callers are permitted to do. If neither
17529 &%trusted_groups%& nor &%trusted_users%& is set, only root and the Exim user
17532 .option trusted_users main "string list&!!" unset
17533 .cindex "trusted users"
17534 .cindex "user" "trusted"
17535 This option is expanded just once, at the start of Exim's processing. If this
17536 option is set, any process that is running as one of the listed users is
17537 trusted. The users can be specified numerically or by name. See section
17538 &<<SECTtrustedadmin>>& for details of what trusted callers are permitted to do.
17539 If neither &%trusted_groups%& nor &%trusted_users%& is set, only root and the
17540 Exim user are trusted.
17542 .option unknown_login main string&!! unset
17543 .cindex "uid (user id)" "unknown caller"
17544 .vindex "&$caller_uid$&"
17545 This is a specialized feature for use in unusual configurations. By default, if
17546 the uid of the caller of Exim cannot be looked up using &[getpwuid()]&, Exim
17547 gives up. The &%unknown_login%& option can be used to set a login name to be
17548 used in this circumstance. It is expanded, so values like &%user$caller_uid%&
17549 can be set. When &%unknown_login%& is used, the value of &%unknown_username%&
17550 is used for the user's real name (gecos field), unless this has been set by the
17553 .option unknown_username main string unset
17554 See &%unknown_login%&.
17556 .option untrusted_set_sender main "address list&!!" unset
17557 .cindex "trusted users"
17558 .cindex "sender" "setting by untrusted user"
17559 .cindex "untrusted user setting sender"
17560 .cindex "user" "untrusted setting sender"
17561 .cindex "envelope sender"
17562 When an untrusted user submits a message to Exim using the standard input, Exim
17563 normally creates an envelope sender address from the user's login and the
17564 default qualification domain. Data from the &%-f%& option (for setting envelope
17565 senders on non-SMTP messages) or the SMTP MAIL command (if &%-bs%& or &%-bS%&
17566 is used) is ignored.
17568 However, untrusted users are permitted to set an empty envelope sender address,
17569 to declare that a message should never generate any bounces. For example:
17571 exim -f '<>' user@domain.example
17573 .vindex "&$sender_ident$&"
17574 The &%untrusted_set_sender%& option allows you to permit untrusted users to set
17575 other envelope sender addresses in a controlled way. When it is set, untrusted
17576 users are allowed to set envelope sender addresses that match any of the
17577 patterns in the list. Like all address lists, the string is expanded. The
17578 identity of the user is in &$sender_ident$&, so you can, for example, restrict
17579 users to setting senders that start with their login ids
17580 followed by a hyphen
17581 by a setting like this:
17583 untrusted_set_sender = ^$sender_ident-
17585 If you want to allow untrusted users to set envelope sender addresses without
17586 restriction, you can use
17588 untrusted_set_sender = *
17590 The &%untrusted_set_sender%& option applies to all forms of local input, but
17591 only to the setting of the envelope sender. It does not permit untrusted users
17592 to use the other options which trusted user can use to override message
17593 parameters. Furthermore, it does not stop Exim from removing an existing
17594 &'Sender:'& header in the message, or from adding a &'Sender:'& header if
17595 necessary. See &%local_sender_retain%& and &%local_from_check%& for ways of
17596 overriding these actions. The handling of the &'Sender:'& header is also
17597 described in section &<<SECTthesenhea>>&.
17599 The log line for a message's arrival shows the envelope sender following
17600 &"<="&. For local messages, the user's login always follows, after &"U="&. In
17601 &%-bp%& displays, and in the Exim monitor, if an untrusted user sets an
17602 envelope sender address, the user's login is shown in parentheses after the
17606 .option uucp_from_pattern main string "see below"
17607 .cindex "&""From""& line"
17608 .cindex "UUCP" "&""From""& line"
17609 Some applications that pass messages to an MTA via a command line interface use
17610 an initial line starting with &"From&~"& to pass the envelope sender. In
17611 particular, this is used by UUCP software. Exim recognizes such a line by means
17612 of a regular expression that is set in &%uucp_from_pattern%&. When the pattern
17613 matches, the sender address is constructed by expanding the contents of
17614 &%uucp_from_sender%&, provided that the caller of Exim is a trusted user. The
17615 default pattern recognizes lines in the following two forms:
17617 From ph10 Fri Jan 5 12:35 GMT 1996
17618 From ph10 Fri, 7 Jan 97 14:00:00 GMT
17620 The pattern can be seen by running
17622 exim -bP uucp_from_pattern
17624 It checks only up to the hours and minutes, and allows for a 2-digit or 4-digit
17625 year in the second case. The first word after &"From&~"& is matched in the
17626 regular expression by a parenthesized subpattern. The default value for
17627 &%uucp_from_sender%& is &"$1"&, which therefore just uses this first word
17628 (&"ph10"& in the example above) as the message's sender. See also
17629 &%ignore_fromline_hosts%&.
17632 .option uucp_from_sender main string&!! &`$1`&
17633 See &%uucp_from_pattern%& above.
17636 .option warn_message_file main string unset
17637 .cindex "warning of delay" "customizing the message"
17638 .cindex "customizing" "warning message"
17639 This option defines a template file containing paragraphs of text to be used
17640 for constructing the warning message which is sent by Exim when a message has
17641 been on the queue for a specified amount of time, as specified by
17642 &%delay_warning%&. Details of the file's contents are given in chapter
17643 &<<CHAPemsgcust>>&. See also &%bounce_message_file%&.
17646 .option write_rejectlog main boolean true
17647 .cindex "reject log" "disabling"
17648 If this option is set false, Exim no longer writes anything to the reject log.
17649 See chapter &<<CHAPlog>>& for details of what Exim writes to its logs.
17650 .ecindex IIDconfima
17651 .ecindex IIDmaiconf
17656 . ////////////////////////////////////////////////////////////////////////////
17657 . ////////////////////////////////////////////////////////////////////////////
17659 .chapter "Generic options for routers" "CHAProutergeneric"
17660 .scindex IIDgenoprou1 "options" "generic; for routers"
17661 .scindex IIDgenoprou2 "generic options" "router"
17662 This chapter describes the generic options that apply to all routers.
17663 Those that are preconditions are marked with ‡ in the &"use"& field.
17665 For a general description of how a router operates, see sections
17666 &<<SECTrunindrou>>& and &<<SECTrouprecon>>&. The latter specifies the order in
17667 which the preconditions are tested. The order of expansion of the options that
17668 provide data for a transport is: &%errors_to%&, &%headers_add%&,
17669 &%headers_remove%&, &%transport%&.
17673 .option address_data routers string&!! unset
17674 .cindex "router" "data attached to address"
17675 The string is expanded just before the router is run, that is, after all the
17676 precondition tests have succeeded. If the expansion is forced to fail, the
17677 router declines, the value of &%address_data%& remains unchanged, and the
17678 &%more%& option controls what happens next. Other expansion failures cause
17679 delivery of the address to be deferred.
17681 .vindex "&$address_data$&"
17682 When the expansion succeeds, the value is retained with the address, and can be
17683 accessed using the variable &$address_data$& in the current router, subsequent
17684 routers, and the eventual transport.
17686 &*Warning*&: If the current or any subsequent router is a &(redirect)& router
17687 that runs a user's filter file, the contents of &$address_data$& are accessible
17688 in the filter. This is not normally a problem, because such data is usually
17689 either not confidential or it &"belongs"& to the current user, but if you do
17690 put confidential data into &$address_data$& you need to remember this point.
17692 Even if the router declines or passes, the value of &$address_data$& remains
17693 with the address, though it can be changed by another &%address_data%& setting
17694 on a subsequent router. If a router generates child addresses, the value of
17695 &$address_data$& propagates to them. This also applies to the special kind of
17696 &"child"& that is generated by a router with the &%unseen%& option.
17698 The idea of &%address_data%& is that you can use it to look up a lot of data
17699 for the address once, and then pick out parts of the data later. For example,
17700 you could use a single LDAP lookup to return a string of the form
17702 uid=1234 gid=5678 mailbox=/mail/xyz forward=/home/xyz/.forward
17704 In the transport you could pick out the mailbox by a setting such as
17706 file = ${extract{mailbox}{$address_data}}
17708 This makes the configuration file less messy, and also reduces the number of
17709 lookups (though Exim does cache lookups).
17711 .vindex "&$sender_address_data$&"
17712 .vindex "&$address_data$&"
17713 The &%address_data%& facility is also useful as a means of passing information
17714 from one router to another, and from a router to a transport. In addition, if
17715 &$address_data$& is set by a router when verifying a recipient address from an
17716 ACL, it remains available for use in the rest of the ACL statement. After
17717 verifying a sender, the value is transferred to &$sender_address_data$&.
17721 .option address_test routers&!? boolean true
17723 .cindex "router" "skipping when address testing"
17724 If this option is set false, the router is skipped when routing is being tested
17725 by means of the &%-bt%& command line option. This can be a convenience when
17726 your first router sends messages to an external scanner, because it saves you
17727 having to set the &"already scanned"& indicator when testing real address
17732 .option cannot_route_message routers string&!! unset
17733 .cindex "router" "customizing &""cannot route""& message"
17734 .cindex "customizing" "&""cannot route""& message"
17735 This option specifies a text message that is used when an address cannot be
17736 routed because Exim has run out of routers. The default message is
17737 &"Unrouteable address"&. This option is useful only on routers that have
17738 &%more%& set false, or on the very last router in a configuration, because the
17739 value that is used is taken from the last router that is considered. This
17740 includes a router that is skipped because its preconditions are not met, as
17741 well as a router that declines. For example, using the default configuration,
17744 cannot_route_message = Remote domain not found in DNS
17746 on the first router, which is a &(dnslookup)& router with &%more%& set false,
17749 cannot_route_message = Unknown local user
17751 on the final router that checks for local users. If string expansion fails for
17752 this option, the default message is used. Unless the expansion failure was
17753 explicitly forced, a message about the failure is written to the main and panic
17754 logs, in addition to the normal message about the routing failure.
17757 .option caseful_local_part routers boolean false
17758 .cindex "case of local parts"
17759 .cindex "router" "case of local parts"
17760 By default, routers handle the local parts of addresses in a case-insensitive
17761 manner, though the actual case is preserved for transmission with the message.
17762 If you want the case of letters to be significant in a router, you must set
17763 this option true. For individual router options that contain address or local
17764 part lists (for example, &%local_parts%&), case-sensitive matching can be
17765 turned on by &"+caseful"& as a list item. See section &<<SECTcasletadd>>& for
17768 .vindex "&$local_part$&"
17769 .vindex "&$original_local_part$&"
17770 .vindex "&$parent_local_part$&"
17771 The value of the &$local_part$& variable is forced to lower case while a
17772 router is running unless &%caseful_local_part%& is set. When a router assigns
17773 an address to a transport, the value of &$local_part$& when the transport runs
17774 is the same as it was in the router. Similarly, when a router generates child
17775 addresses by aliasing or forwarding, the values of &$original_local_part$&
17776 and &$parent_local_part$& are those that were used by the redirecting router.
17778 This option applies to the processing of an address by a router. When a
17779 recipient address is being processed in an ACL, there is a separate &%control%&
17780 modifier that can be used to specify case-sensitive processing within the ACL
17781 (see section &<<SECTcontrols>>&).
17785 .option check_local_user routers&!? boolean false
17786 .cindex "local user, checking in router"
17787 .cindex "router" "checking for local user"
17788 .cindex "&_/etc/passwd_&"
17790 When this option is true, Exim checks that the local part of the recipient
17791 address (with affixes removed if relevant) is the name of an account on the
17792 local system. The check is done by calling the &[getpwnam()]& function rather
17793 than trying to read &_/etc/passwd_& directly. This means that other methods of
17794 holding password data (such as NIS) are supported. If the local part is a local
17795 user, &$home$& is set from the password data, and can be tested in other
17796 preconditions that are evaluated after this one (the order of evaluation is
17797 given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
17798 overridden by &%router_home_directory%&. If the local part is not a local user,
17799 the router is skipped.
17801 If you want to check that the local part is either the name of a local user
17802 or matches something else, you cannot combine &%check_local_user%& with a
17803 setting of &%local_parts%&, because that specifies the logical &'and'& of the
17804 two conditions. However, you can use a &(passwd)& lookup in a &%local_parts%&
17805 setting to achieve this. For example:
17807 local_parts = passwd;$local_part : lsearch;/etc/other/users
17809 Note, however, that the side effects of &%check_local_user%& (such as setting
17810 up a home directory) do not occur when a &(passwd)& lookup is used in a
17811 &%local_parts%& (or any other) precondition.
17815 .option condition routers&!? string&!! unset
17816 .cindex "router" "customized precondition"
17817 This option specifies a general precondition test that has to succeed for the
17818 router to be called. The &%condition%& option is the last precondition to be
17819 evaluated (see section &<<SECTrouprecon>>&). The string is expanded, and if the
17820 result is a forced failure, or an empty string, or one of the strings &"0"& or
17821 &"no"& or &"false"& (checked without regard to the case of the letters), the
17822 router is skipped, and the address is offered to the next one.
17824 If the result is any other value, the router is run (as this is the last
17825 precondition to be evaluated, all the other preconditions must be true).
17827 This option is unusual in that multiple &%condition%& options may be present.
17828 All &%condition%& options must succeed.
17830 The &%condition%& option provides a means of applying custom conditions to the
17831 running of routers. Note that in the case of a simple conditional expansion,
17832 the default expansion values are exactly what is wanted. For example:
17834 condition = ${if >{$message_age}{600}}
17836 Because of the default behaviour of the string expansion, this is equivalent to
17838 condition = ${if >{$message_age}{600}{true}{}}
17841 A multiple condition example, which succeeds:
17843 condition = ${if >{$message_age}{600}}
17844 condition = ${if !eq{${lc:$local_part}}{postmaster}}
17848 If the expansion fails (other than forced failure) delivery is deferred. Some
17849 of the other precondition options are common special cases that could in fact
17850 be specified using &%condition%&.
17852 Historical note: We have &%condition%& on ACLs and on Routers. Routers
17853 are far older, and use one set of semantics. ACLs are newer and when
17854 they were created, the ACL &%condition%& process was given far stricter
17855 parse semantics. The &%bool{}%& expansion condition uses the same rules as
17856 ACLs. The &%bool_lax{}%& expansion condition uses the same rules as
17857 Routers. More pointedly, the &%bool_lax{}%& was written to match the existing
17858 Router rules processing behavior.
17860 This is best illustrated in an example:
17862 # If used in an ACL condition will fail with a syntax error, but
17863 # in a router condition any extra characters are treated as a string
17865 $ exim -be '${if eq {${lc:GOOGLE.com}} {google.com}} {yes} {no}}'
17868 $ exim -be '${if eq {${lc:WHOIS.com}} {google.com}} {yes} {no}}'
17871 In each example above, the &%if%& statement actually ends after
17872 &"{google.com}}"&. Since no true or false braces were defined, the
17873 default &%if%& behavior is to return a boolean true or a null answer
17874 (which evaluates to false). The rest of the line is then treated as a
17875 string. So the first example resulted in the boolean answer &"true"&
17876 with the string &" {yes} {no}}"& appended to it. The second example
17877 resulted in the null output (indicating false) with the string
17878 &" {yes} {no}}"& appended to it.
17880 In fact you can put excess forward braces in too. In the router
17881 &%condition%&, Exim's parser only looks for &"{"& symbols when they
17882 mean something, like after a &"$"& or when required as part of a
17883 conditional. But otherwise &"{"& and &"}"& are treated as ordinary
17886 Thus, in a Router, the above expansion strings will both always evaluate
17887 true, as the result of expansion is a non-empty string which doesn't
17888 match an explicit false value. This can be tricky to debug. By
17889 contrast, in an ACL either of those strings will always result in an
17890 expansion error because the result doesn't look sufficiently boolean.
17893 .option debug_print routers string&!! unset
17894 .cindex "testing" "variables in drivers"
17895 If this option is set and debugging is enabled (see the &%-d%& command line
17896 option) or in address-testing mode (see the &%-bt%& command line option),
17897 the string is expanded and included in the debugging output.
17898 If expansion of the string fails, the error message is written to the debugging
17899 output, and Exim carries on processing.
17900 This option is provided to help with checking out the values of variables and
17901 so on when debugging router configurations. For example, if a &%condition%&
17902 option appears not to be working, &%debug_print%& can be used to output the
17903 variables it references. The output happens after checks for &%domains%&,
17904 &%local_parts%&, and &%check_local_user%& but before any other preconditions
17905 are tested. A newline is added to the text if it does not end with one.
17906 The variable &$router_name$& contains the name of the router.
17910 .option disable_logging routers boolean false
17911 If this option is set true, nothing is logged for any routing errors
17912 or for any deliveries caused by this router. You should not set this option
17913 unless you really, really know what you are doing. See also the generic
17914 transport option of the same name.
17916 .option dnssec_request_domains routers "domain list&!!" unset
17917 .cindex "MX record" "security"
17918 .cindex "DNSSEC" "MX lookup"
17919 .cindex "security" "MX lookup"
17920 .cindex "DNS" "DNSSEC"
17921 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
17922 the dnssec request bit set.
17923 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17925 .option dnssec_require_domains routers "domain list&!!" unset
17926 .cindex "MX record" "security"
17927 .cindex "DNSSEC" "MX lookup"
17928 .cindex "security" "MX lookup"
17929 .cindex "DNS" "DNSSEC"
17930 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
17931 the dnssec request bit set. Any returns not having the Authenticated Data bit
17932 (AD bit) set will be ignored and logged as a host-lookup failure.
17933 This applies to all of the SRV, MX, AAAA, A lookup sequence.
17936 .option domains routers&!? "domain list&!!" unset
17937 .cindex "router" "restricting to specific domains"
17938 .vindex "&$domain_data$&"
17939 If this option is set, the router is skipped unless the current domain matches
17940 the list. If the match is achieved by means of a file lookup, the data that the
17941 lookup returned for the domain is placed in &$domain_data$& for use in string
17942 expansions of the driver's private options. See section &<<SECTrouprecon>>& for
17943 a list of the order in which preconditions are evaluated.
17947 .option driver routers string unset
17948 This option must always be set. It specifies which of the available routers is
17952 .option dsn_lasthop routers boolean false
17953 .cindex "DSN" "success"
17954 .cindex "Delivery Status Notification" "success"
17955 If this option is set true, and extended DSN (RFC3461) processing is in effect,
17956 Exim will not pass on DSN requests to downstream DSN-aware hosts but will
17957 instead send a success DSN as if the next hop does not support DSN.
17958 Not effective on redirect routers.
17962 .option errors_to routers string&!! unset
17963 .cindex "envelope sender"
17964 .cindex "router" "changing address for errors"
17965 If a router successfully handles an address, it may assign the address to a
17966 transport for delivery or it may generate child addresses. In both cases, if
17967 there is a delivery problem during later processing, the resulting bounce
17968 message is sent to the address that results from expanding this string,
17969 provided that the address verifies successfully. The &%errors_to%& option is
17970 expanded before &%headers_add%&, &%headers_remove%&, and &%transport%&.
17972 The &%errors_to%& setting associated with an address can be overridden if it
17973 subsequently passes through other routers that have their own &%errors_to%&
17974 settings, or if the message is delivered by a transport with a &%return_path%&
17977 If &%errors_to%& is unset, or the expansion is forced to fail, or the result of
17978 the expansion fails to verify, the errors address associated with the incoming
17979 address is used. At top level, this is the envelope sender. A non-forced
17980 expansion failure causes delivery to be deferred.
17982 If an address for which &%errors_to%& has been set ends up being delivered over
17983 SMTP, the envelope sender for that delivery is the &%errors_to%& value, so that
17984 any bounces that are generated by other MTAs on the delivery route are also
17985 sent there. You can set &%errors_to%& to the empty string by either of these
17991 An expansion item that yields an empty string has the same effect. If you do
17992 this, a locally detected delivery error for addresses processed by this router
17993 no longer gives rise to a bounce message; the error is discarded. If the
17994 address is delivered to a remote host, the return path is set to &`<>`&, unless
17995 overridden by the &%return_path%& option on the transport.
17997 .vindex "&$address_data$&"
17998 If for some reason you want to discard local errors, but use a non-empty
17999 MAIL command for remote delivery, you can preserve the original return
18000 path in &$address_data$& in the router, and reinstate it in the transport by
18001 setting &%return_path%&.
18003 The most common use of &%errors_to%& is to direct mailing list bounces to the
18004 manager of the list, as described in section &<<SECTmailinglists>>&, or to
18005 implement VERP (Variable Envelope Return Paths) (see section &<<SECTverp>>&).
18009 .option expn routers&!? boolean true
18010 .cindex "address" "testing"
18011 .cindex "testing" "addresses"
18012 .cindex "EXPN" "router skipping"
18013 .cindex "router" "skipping for EXPN"
18014 If this option is turned off, the router is skipped when testing an address
18015 as a result of processing an SMTP EXPN command. You might, for example,
18016 want to turn it off on a router for users' &_.forward_& files, while leaving it
18017 on for the system alias file.
18018 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18021 The use of the SMTP EXPN command is controlled by an ACL (see chapter
18022 &<<CHAPACL>>&). When Exim is running an EXPN command, it is similar to testing
18023 an address with &%-bt%&. Compare VRFY, whose counterpart is &%-bv%&.
18027 .option fail_verify routers boolean false
18028 .cindex "router" "forcing verification failure"
18029 Setting this option has the effect of setting both &%fail_verify_sender%& and
18030 &%fail_verify_recipient%& to the same value.
18034 .option fail_verify_recipient routers boolean false
18035 If this option is true and an address is accepted by this router when
18036 verifying a recipient, verification fails.
18040 .option fail_verify_sender routers boolean false
18041 If this option is true and an address is accepted by this router when
18042 verifying a sender, verification fails.
18046 .option fallback_hosts routers "string list" unset
18047 .cindex "router" "fallback hosts"
18048 .cindex "fallback" "hosts specified on router"
18049 String expansion is not applied to this option. The argument must be a
18050 colon-separated list of host names or IP addresses. The list separator can be
18051 changed (see section &<<SECTlistconstruct>>&), and a port can be specified with
18052 each name or address. In fact, the format of each item is exactly the same as
18053 defined for the list of hosts in a &(manualroute)& router (see section
18054 &<<SECTformatonehostitem>>&).
18056 If a router queues an address for a remote transport, this host list is
18057 associated with the address, and used instead of the transport's fallback host
18058 list. If &%hosts_randomize%& is set on the transport, the order of the list is
18059 randomized for each use. See the &%fallback_hosts%& option of the &(smtp)&
18060 transport for further details.
18063 .option group routers string&!! "see below"
18064 .cindex "gid (group id)" "local delivery"
18065 .cindex "local transports" "uid and gid"
18066 .cindex "transport" "local"
18067 .cindex "router" "setting group"
18068 When a router queues an address for a transport, and the transport does not
18069 specify a group, the group given here is used when running the delivery
18071 The group may be specified numerically or by name. If expansion fails, the
18072 error is logged and delivery is deferred.
18073 The default is unset, unless &%check_local_user%& is set, when the default
18074 is taken from the password information. See also &%initgroups%& and &%user%&
18075 and the discussion in chapter &<<CHAPenvironment>>&.
18079 .option headers_add routers list&!! unset
18080 .cindex "header lines" "adding"
18081 .cindex "router" "adding header lines"
18082 This option specifies a list of text headers,
18083 newline-separated (by default, changeable in the usual way),
18084 that is associated with any addresses that are accepted by the router.
18085 Each item is separately expanded, at routing time. However, this
18086 option has no effect when an address is just being verified. The way in which
18087 the text is used to add header lines at transport time is described in section
18088 &<<SECTheadersaddrem>>&. New header lines are not actually added until the
18089 message is in the process of being transported. This means that references to
18090 header lines in string expansions in the transport's configuration do not
18091 &"see"& the added header lines.
18093 The &%headers_add%& option is expanded after &%errors_to%&, but before
18094 &%headers_remove%& and &%transport%&. If an item is empty, or if
18095 an item expansion is forced to fail, the item has no effect. Other expansion
18096 failures are treated as configuration errors.
18098 Unlike most options, &%headers_add%& can be specified multiple times
18099 for a router; all listed headers are added.
18101 &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)&
18102 router that has the &%one_time%& option set.
18104 .cindex "duplicate addresses"
18105 .oindex "&%unseen%&"
18106 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
18107 additions are deleted when the address is passed on to subsequent routers.
18108 For a &%redirect%& router, if a generated address is the same as the incoming
18109 address, this can lead to duplicate addresses with different header
18110 modifications. Exim does not do duplicate deliveries (except, in certain
18111 circumstances, to pipes -- see section &<<SECTdupaddr>>&), but it is undefined
18112 which of the duplicates is discarded, so this ambiguous situation should be
18113 avoided. The &%repeat_use%& option of the &%redirect%& router may be of help.
18117 .option headers_remove routers list&!! unset
18118 .cindex "header lines" "removing"
18119 .cindex "router" "removing header lines"
18120 This option specifies a list of text headers,
18121 colon-separated (by default, changeable in the usual way),
18122 that is associated with any addresses that are accepted by the router.
18123 Each item is separately expanded, at routing time. However, this
18124 option has no effect when an address is just being verified. The way in which
18125 the text is used to remove header lines at transport time is described in
18126 section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
18127 the message is in the process of being transported. This means that references
18128 to header lines in string expansions in the transport's configuration still
18129 &"see"& the original header lines.
18131 The &%headers_remove%& option is expanded after &%errors_to%& and
18132 &%headers_add%&, but before &%transport%&. If an item expansion is forced to fail,
18133 the item has no effect. Other expansion failures are treated as configuration
18136 Unlike most options, &%headers_remove%& can be specified multiple times
18137 for a router; all listed headers are removed.
18139 &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)&
18140 router that has the &%one_time%& option set.
18142 &*Warning 2*&: If the &%unseen%& option is set on the router, all header
18143 removal requests are deleted when the address is passed on to subsequent
18144 routers, and this can lead to problems with duplicates -- see the similar
18145 warning for &%headers_add%& above.
18147 &*Warning 3*&: Because of the separate expansion of the list items,
18148 items that contain a list separator must have it doubled.
18149 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
18153 .option ignore_target_hosts routers "host list&!!" unset
18154 .cindex "IP address" "discarding"
18155 .cindex "router" "discarding IP addresses"
18156 Although this option is a host list, it should normally contain IP address
18157 entries rather than names. If any host that is looked up by the router has an
18158 IP address that matches an item in this list, Exim behaves as if that IP
18159 address did not exist. This option allows you to cope with rogue DNS entries
18162 remote.domain.example. A 127.0.0.1
18166 ignore_target_hosts = 127.0.0.1
18168 on the relevant router. If all the hosts found by a &(dnslookup)& router are
18169 discarded in this way, the router declines. In a conventional configuration, an
18170 attempt to mail to such a domain would normally provoke the &"unrouteable
18171 domain"& error, and an attempt to verify an address in the domain would fail.
18172 Similarly, if &%ignore_target_hosts%& is set on an &(ipliteral)& router, the
18173 router declines if presented with one of the listed addresses.
18175 You can use this option to disable the use of IPv4 or IPv6 for mail delivery by
18176 means of the first or the second of the following settings, respectively:
18178 ignore_target_hosts = 0.0.0.0/0
18179 ignore_target_hosts = <; 0::0/0
18181 The pattern in the first line matches all IPv4 addresses, whereas the pattern
18182 in the second line matches all IPv6 addresses.
18184 This option may also be useful for ignoring link-local and site-local IPv6
18185 addresses. Because, like all host lists, the value of &%ignore_target_hosts%&
18186 is expanded before use as a list, it is possible to make it dependent on the
18187 domain that is being routed.
18189 .vindex "&$host_address$&"
18190 During its expansion, &$host_address$& is set to the IP address that is being
18193 .option initgroups routers boolean false
18194 .cindex "additional groups"
18195 .cindex "groups" "additional"
18196 .cindex "local transports" "uid and gid"
18197 .cindex "transport" "local"
18198 If the router queues an address for a transport, and this option is true, and
18199 the uid supplied by the router is not overridden by the transport, the
18200 &[initgroups()]& function is called when running the transport to ensure that
18201 any additional groups associated with the uid are set up. See also &%group%&
18202 and &%user%& and the discussion in chapter &<<CHAPenvironment>>&.
18206 .option local_part_prefix routers&!? "string list" unset
18207 .cindex "router" "prefix for local part"
18208 .cindex "prefix" "for local part, used in router"
18209 If this option is set, the router is skipped unless the local part starts with
18210 one of the given strings, or &%local_part_prefix_optional%& is true. See
18211 section &<<SECTrouprecon>>& for a list of the order in which preconditions are
18214 The list is scanned from left to right, and the first prefix that matches is
18215 used. A limited form of wildcard is available; if the prefix begins with an
18216 asterisk, it matches the longest possible sequence of arbitrary characters at
18217 the start of the local part. An asterisk should therefore always be followed by
18218 some character that does not occur in normal local parts.
18219 .cindex "multiple mailboxes"
18220 .cindex "mailbox" "multiple"
18221 Wildcarding can be used to set up multiple user mailboxes, as described in
18222 section &<<SECTmulbox>>&.
18224 .vindex "&$local_part$&"
18225 .vindex "&$local_part_prefix$&"
18226 During the testing of the &%local_parts%& option, and while the router is
18227 running, the prefix is removed from the local part, and is available in the
18228 expansion variable &$local_part_prefix$&. When a message is being delivered, if
18229 the router accepts the address, this remains true during subsequent delivery by
18230 a transport. In particular, the local part that is transmitted in the RCPT
18231 command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default.
18232 This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
18233 the relevant transport.
18235 When an address is being verified, &%local_part_prefix%& affects only the
18236 behaviour of the router. If the callout feature of verification is in use, this
18237 means that the full address, including the prefix, will be used during the
18240 The prefix facility is commonly used to handle local parts of the form
18241 &%owner-something%&. Another common use is to support local parts of the form
18242 &%real-username%& to bypass a user's &_.forward_& file &-- helpful when trying
18243 to tell a user their forwarding is broken &-- by placing a router like this one
18244 immediately before the router that handles &_.forward_& files:
18248 local_part_prefix = real-
18250 transport = local_delivery
18252 For security, it would probably be a good idea to restrict the use of this
18253 router to locally-generated messages, using a condition such as this:
18255 condition = ${if match {$sender_host_address}\
18256 {\N^(|127\.0\.0\.1)$\N}}
18259 If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router,
18260 both conditions must be met if not optional. Care must be taken if wildcards
18261 are used in both a prefix and a suffix on the same router. Different
18262 separator characters must be used to avoid ambiguity.
18265 .option local_part_prefix_optional routers boolean false
18266 See &%local_part_prefix%& above.
18270 .option local_part_suffix routers&!? "string list" unset
18271 .cindex "router" "suffix for local part"
18272 .cindex "suffix for local part" "used in router"
18273 This option operates in the same way as &%local_part_prefix%&, except that the
18274 local part must end (rather than start) with the given string, the
18275 &%local_part_suffix_optional%& option determines whether the suffix is
18276 mandatory, and the wildcard * character, if present, must be the last
18277 character of the suffix. This option facility is commonly used to handle local
18278 parts of the form &%something-request%& and multiple user mailboxes of the form
18282 .option local_part_suffix_optional routers boolean false
18283 See &%local_part_suffix%& above.
18287 .option local_parts routers&!? "local part list&!!" unset
18288 .cindex "router" "restricting to specific local parts"
18289 .cindex "local part" "checking in router"
18290 The router is run only if the local part of the address matches the list.
18291 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18293 section &<<SECTlocparlis>>& for a discussion of local part lists. Because the
18294 string is expanded, it is possible to make it depend on the domain, for
18297 local_parts = dbm;/usr/local/specials/$domain
18299 .vindex "&$local_part_data$&"
18300 If the match is achieved by a lookup, the data that the lookup returned
18301 for the local part is placed in the variable &$local_part_data$& for use in
18302 expansions of the router's private options. You might use this option, for
18303 example, if you have a large number of local virtual domains, and you want to
18304 send all postmaster mail to the same place without having to set up an alias in
18305 each virtual domain:
18309 local_parts = postmaster
18310 data = postmaster@real.domain.example
18314 .option log_as_local routers boolean "see below"
18315 .cindex "log" "delivery line"
18316 .cindex "delivery" "log line format"
18317 Exim has two logging styles for delivery, the idea being to make local
18318 deliveries stand out more visibly from remote ones. In the &"local"& style, the
18319 recipient address is given just as the local part, without a domain. The use of
18320 this style is controlled by this option. It defaults to true for the &(accept)&
18321 router, and false for all the others. This option applies only when a
18322 router assigns an address to a transport. It has no effect on routers that
18323 redirect addresses.
18327 .option more routers boolean&!! true
18328 The result of string expansion for this option must be a valid boolean value,
18329 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
18330 result causes an error, and delivery is deferred. If the expansion is forced to
18331 fail, the default value for the option (true) is used. Other failures cause
18332 delivery to be deferred.
18334 If this option is set false, and the router declines to handle the address, no
18335 further routers are tried, routing fails, and the address is bounced.
18337 However, if the router explicitly passes an address to the following router by
18338 means of the setting
18342 or otherwise, the setting of &%more%& is ignored. Also, the setting of &%more%&
18343 does not affect the behaviour if one of the precondition tests fails. In that
18344 case, the address is always passed to the next router.
18346 Note that &%address_data%& is not considered to be a precondition. If its
18347 expansion is forced to fail, the router declines, and the value of &%more%&
18348 controls what happens next.
18351 .option pass_on_timeout routers boolean false
18352 .cindex "timeout" "of router"
18353 .cindex "router" "timeout"
18354 If a router times out during a host lookup, it normally causes deferral of the
18355 address. If &%pass_on_timeout%& is set, the address is passed on to the next
18356 router, overriding &%no_more%&. This may be helpful for systems that are
18357 intermittently connected to the Internet, or those that want to pass to a smart
18358 host any messages that cannot immediately be delivered.
18360 There are occasional other temporary errors that can occur while doing DNS
18361 lookups. They are treated in the same way as a timeout, and this option
18362 applies to all of them.
18366 .option pass_router routers string unset
18367 .cindex "router" "go to after &""pass""&"
18368 Routers that recognize the generic &%self%& option (&(dnslookup)&,
18369 &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing
18370 routing to continue, and overriding a false setting of &%more%&. When one of
18371 these routers returns &"pass"&, the address is normally handed on to the next
18372 router in sequence. This can be changed by setting &%pass_router%& to the name
18373 of another router. However (unlike &%redirect_router%&) the named router must
18374 be below the current router, to avoid loops. Note that this option applies only
18375 to the special case of &"pass"&. It does not apply when a router returns
18376 &"decline"& because it cannot handle an address.
18380 .option redirect_router routers string unset
18381 .cindex "router" "start at after redirection"
18382 Sometimes an administrator knows that it is pointless to reprocess addresses
18383 generated from alias or forward files with the same router again. For
18384 example, if an alias file translates real names into login ids there is no
18385 point searching the alias file a second time, especially if it is a large file.
18387 The &%redirect_router%& option can be set to the name of any router instance.
18388 It causes the routing of any generated addresses to start at the named router
18389 instead of at the first router. This option has no effect if the router in
18390 which it is set does not generate new addresses.
18394 .option require_files routers&!? "string list&!!" unset
18395 .cindex "file" "requiring for router"
18396 .cindex "router" "requiring file existence"
18397 This option provides a general mechanism for predicating the running of a
18398 router on the existence or non-existence of certain files or directories.
18399 Before running a router, as one of its precondition tests, Exim works its way
18400 through the &%require_files%& list, expanding each item separately.
18402 Because the list is split before expansion, any colons in expansion items must
18403 be doubled, or the facility for using a different list separator must be used.
18404 If any expansion is forced to fail, the item is ignored. Other expansion
18405 failures cause routing of the address to be deferred.
18407 If any expanded string is empty, it is ignored. Otherwise, except as described
18408 below, each string must be a fully qualified file path, optionally preceded by
18409 &"!"&. The paths are passed to the &[stat()]& function to test for the
18410 existence of the files or directories. The router is skipped if any paths not
18411 preceded by &"!"& do not exist, or if any paths preceded by &"!"& do exist.
18414 If &[stat()]& cannot determine whether a file exists or not, delivery of
18415 the message is deferred. This can happen when NFS-mounted filesystems are
18418 This option is checked after the &%domains%&, &%local_parts%&, and &%senders%&
18419 options, so you cannot use it to check for the existence of a file in which to
18420 look up a domain, local part, or sender. (See section &<<SECTrouprecon>>& for a
18421 full list of the order in which preconditions are evaluated.) However, as
18422 these options are all expanded, you can use the &%exists%& expansion condition
18423 to make such tests. The &%require_files%& option is intended for checking files
18424 that the router may be going to use internally, or which are needed by a
18425 transport (for example &_.procmailrc_&).
18427 During delivery, the &[stat()]& function is run as root, but there is a
18428 facility for some checking of the accessibility of a file by another user.
18429 This is not a proper permissions check, but just a &"rough"& check that
18430 operates as follows:
18432 If an item in a &%require_files%& list does not contain any forward slash
18433 characters, it is taken to be the user (and optional group, separated by a
18434 comma) to be checked for subsequent files in the list. If no group is specified
18435 but the user is specified symbolically, the gid associated with the uid is
18438 require_files = mail:/some/file
18439 require_files = $local_part:$home/.procmailrc
18441 If a user or group name in a &%require_files%& list does not exist, the
18442 &%require_files%& condition fails.
18444 Exim performs the check by scanning along the components of the file path, and
18445 checking the access for the given uid and gid. It checks for &"x"& access on
18446 directories, and &"r"& access on the final file. Note that this means that file
18447 access control lists, if the operating system has them, are ignored.
18449 &*Warning 1*&: When the router is being run to verify addresses for an
18450 incoming SMTP message, Exim is not running as root, but under its own uid. This
18451 may affect the result of a &%require_files%& check. In particular, &[stat()]&
18452 may yield the error EACCES (&"Permission denied"&). This means that the Exim
18453 user is not permitted to read one of the directories on the file's path.
18455 &*Warning 2*&: Even when Exim is running as root while delivering a message,
18456 &[stat()]& can yield EACCES for a file in an NFS directory that is mounted
18457 without root access. In this case, if a check for access by a particular user
18458 is requested, Exim creates a subprocess that runs as that user, and tries the
18459 check again in that process.
18461 The default action for handling an unresolved EACCES is to consider it to
18462 be caused by a configuration error, and routing is deferred because the
18463 existence or non-existence of the file cannot be determined. However, in some
18464 circumstances it may be desirable to treat this condition as if the file did
18465 not exist. If the file name (or the exclamation mark that precedes the file
18466 name for non-existence) is preceded by a plus sign, the EACCES error is treated
18467 as if the file did not exist. For example:
18469 require_files = +/some/file
18471 If the router is not an essential part of verification (for example, it
18472 handles users' &_.forward_& files), another solution is to set the &%verify%&
18473 option false so that the router is skipped when verifying.
18477 .option retry_use_local_part routers boolean "see below"
18478 .cindex "hints database" "retry keys"
18479 .cindex "local part" "in retry keys"
18480 When a delivery suffers a temporary routing failure, a retry record is created
18481 in Exim's hints database. For addresses whose routing depends only on the
18482 domain, the key for the retry record should not involve the local part, but for
18483 other addresses, both the domain and the local part should be included.
18484 Usually, remote routing is of the former kind, and local routing is of the
18487 This option controls whether the local part is used to form the key for retry
18488 hints for addresses that suffer temporary errors while being handled by this
18489 router. The default value is true for any router that has &%check_local_user%&
18490 set, and false otherwise. Note that this option does not apply to hints keys
18491 for transport delays; they are controlled by a generic transport option of the
18494 The setting of &%retry_use_local_part%& applies only to the router on which it
18495 appears. If the router generates child addresses, they are routed
18496 independently; this setting does not become attached to them.
18500 .option router_home_directory routers string&!! unset
18501 .cindex "router" "home directory for"
18502 .cindex "home directory" "for router"
18504 This option sets a home directory for use while the router is running. (Compare
18505 &%transport_home_directory%&, which sets a home directory for later
18506 transporting.) In particular, if used on a &(redirect)& router, this option
18507 sets a value for &$home$& while a filter is running. The value is expanded;
18508 forced expansion failure causes the option to be ignored &-- other failures
18509 cause the router to defer.
18511 Expansion of &%router_home_directory%& happens immediately after the
18512 &%check_local_user%& test (if configured), before any further expansions take
18514 (See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18516 While the router is running, &%router_home_directory%& overrides the value of
18517 &$home$& that came from &%check_local_user%&.
18519 When a router accepts an address and assigns it to a local transport (including
18520 the cases when a &(redirect)& router generates a pipe, file, or autoreply
18521 delivery), the home directory setting for the transport is taken from the first
18522 of these values that is set:
18525 The &%home_directory%& option on the transport;
18527 The &%transport_home_directory%& option on the router;
18529 The password data if &%check_local_user%& is set on the router;
18531 The &%router_home_directory%& option on the router.
18534 In other words, &%router_home_directory%& overrides the password data for the
18535 router, but not for the transport.
18539 .option self routers string freeze
18540 .cindex "MX record" "pointing to local host"
18541 .cindex "local host" "MX pointing to"
18542 This option applies to those routers that use a recipient address to find a
18543 list of remote hosts. Currently, these are the &(dnslookup)&, &(ipliteral)&,
18544 and &(manualroute)& routers.
18545 Certain configurations of the &(queryprogram)& router can also specify a list
18547 Usually such routers are configured to send the message to a remote host via an
18548 &(smtp)& transport. The &%self%& option specifies what happens when the first
18549 host on the list turns out to be the local host.
18550 The way in which Exim checks for the local host is described in section
18551 &<<SECTreclocipadd>>&.
18553 Normally this situation indicates either an error in Exim's configuration (for
18554 example, the router should be configured not to process this domain), or an
18555 error in the DNS (for example, the MX should not point to this host). For this
18556 reason, the default action is to log the incident, defer the address, and
18557 freeze the message. The following alternatives are provided for use in special
18562 Delivery of the message is tried again later, but the message is not frozen.
18564 .vitem "&%reroute%&: <&'domain'&>"
18565 The domain is changed to the given domain, and the address is passed back to
18566 be reprocessed by the routers. No rewriting of headers takes place. This
18567 behaviour is essentially a redirection.
18569 .vitem "&%reroute: rewrite:%& <&'domain'&>"
18570 The domain is changed to the given domain, and the address is passed back to be
18571 reprocessed by the routers. Any headers that contain the original domain are
18576 .vindex "&$self_hostname$&"
18577 The router passes the address to the next router, or to the router named in the
18578 &%pass_router%& option if it is set. This overrides &%no_more%&. During
18579 subsequent routing and delivery, the variable &$self_hostname$& contains the
18580 name of the local host that the router encountered. This can be used to
18581 distinguish between different cases for hosts with multiple names. The
18587 ensures that only those addresses that routed to the local host are passed on.
18588 Without &%no_more%&, addresses that were declined for other reasons would also
18589 be passed to the next router.
18592 Delivery fails and an error report is generated.
18595 .cindex "local host" "sending to"
18596 The anomaly is ignored and the address is queued for the transport. This
18597 setting should be used with extreme caution. For an &(smtp)& transport, it
18598 makes sense only in cases where the program that is listening on the SMTP port
18599 is not this version of Exim. That is, it must be some other MTA, or Exim with a
18600 different configuration file that handles the domain in another way.
18605 .option senders routers&!? "address list&!!" unset
18606 .cindex "router" "checking senders"
18607 If this option is set, the router is skipped unless the message's sender
18608 address matches something on the list.
18609 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18612 There are issues concerning verification when the running of routers is
18613 dependent on the sender. When Exim is verifying the address in an &%errors_to%&
18614 setting, it sets the sender to the null string. When using the &%-bt%& option
18615 to check a configuration file, it is necessary also to use the &%-f%& option to
18616 set an appropriate sender. For incoming mail, the sender is unset when
18617 verifying the sender, but is available when verifying any recipients. If the
18618 SMTP VRFY command is enabled, it must be used after MAIL if the sender address
18622 .option translate_ip_address routers string&!! unset
18623 .cindex "IP address" "translating"
18624 .cindex "packet radio"
18625 .cindex "router" "IP address translation"
18626 There exist some rare networking situations (for example, packet radio) where
18627 it is helpful to be able to translate IP addresses generated by normal routing
18628 mechanisms into other IP addresses, thus performing a kind of manual IP
18629 routing. This should be done only if the normal IP routing of the TCP/IP stack
18630 is inadequate or broken. Because this is an extremely uncommon requirement, the
18631 code to support this option is not included in the Exim binary unless
18632 SUPPORT_TRANSLATE_IP_ADDRESS=yes is set in &_Local/Makefile_&.
18634 .vindex "&$host_address$&"
18635 The &%translate_ip_address%& string is expanded for every IP address generated
18636 by the router, with the generated address set in &$host_address$&. If the
18637 expansion is forced to fail, no action is taken.
18638 For any other expansion error, delivery of the message is deferred.
18639 If the result of the expansion is an IP address, that replaces the original
18640 address; otherwise the result is assumed to be a host name &-- this is looked
18641 up using &[gethostbyname()]& (or &[getipnodebyname()]& when available) to
18642 produce one or more replacement IP addresses. For example, to subvert all IP
18643 addresses in some specific networks, this could be added to a router:
18645 translate_ip_address = \
18646 ${lookup{${mask:$host_address/26}}lsearch{/some/file}\
18649 The file would contain lines like
18651 10.2.3.128/26 some.host
18652 10.8.4.34/26 10.44.8.15
18654 You should not make use of this facility unless you really understand what you
18659 .option transport routers string&!! unset
18660 This option specifies the transport to be used when a router accepts an address
18661 and sets it up for delivery. A transport is never needed if a router is used
18662 only for verification. The value of the option is expanded at routing time,
18663 after the expansion of &%errors_to%&, &%headers_add%&, and &%headers_remove%&,
18664 and result must be the name of one of the configured transports. If it is not,
18665 delivery is deferred.
18667 The &%transport%& option is not used by the &(redirect)& router, but it does
18668 have some private options that set up transports for pipe and file deliveries
18669 (see chapter &<<CHAPredirect>>&).
18673 .option transport_current_directory routers string&!! unset
18674 .cindex "current directory for local transport"
18675 This option associates a current directory with any address that is routed
18676 to a local transport. This can happen either because a transport is
18677 explicitly configured for the router, or because it generates a delivery to a
18678 file or a pipe. During the delivery process (that is, at transport time), this
18679 option string is expanded and is set as the current directory, unless
18680 overridden by a setting on the transport.
18681 If the expansion fails for any reason, including forced failure, an error is
18682 logged, and delivery is deferred.
18683 See chapter &<<CHAPenvironment>>& for details of the local delivery
18689 .option transport_home_directory routers string&!! "see below"
18690 .cindex "home directory" "for local transport"
18691 This option associates a home directory with any address that is routed to a
18692 local transport. This can happen either because a transport is explicitly
18693 configured for the router, or because it generates a delivery to a file or a
18694 pipe. During the delivery process (that is, at transport time), the option
18695 string is expanded and is set as the home directory, unless overridden by a
18696 setting of &%home_directory%& on the transport.
18697 If the expansion fails for any reason, including forced failure, an error is
18698 logged, and delivery is deferred.
18700 If the transport does not specify a home directory, and
18701 &%transport_home_directory%& is not set for the router, the home directory for
18702 the transport is taken from the password data if &%check_local_user%& is set for
18703 the router. Otherwise it is taken from &%router_home_directory%& if that option
18704 is set; if not, no home directory is set for the transport.
18706 See chapter &<<CHAPenvironment>>& for further details of the local delivery
18712 .option unseen routers boolean&!! false
18713 .cindex "router" "carrying on after success"
18714 The result of string expansion for this option must be a valid boolean value,
18715 that is, one of the strings &"yes"&, &"no"&, &"true"&, or &"false"&. Any other
18716 result causes an error, and delivery is deferred. If the expansion is forced to
18717 fail, the default value for the option (false) is used. Other failures cause
18718 delivery to be deferred.
18720 When this option is set true, routing does not cease if the router accepts the
18721 address. Instead, a copy of the incoming address is passed to the next router,
18722 overriding a false setting of &%more%&. There is little point in setting
18723 &%more%& false if &%unseen%& is always true, but it may be useful in cases when
18724 the value of &%unseen%& contains expansion items (and therefore, presumably, is
18725 sometimes true and sometimes false).
18727 .cindex "copy of message (&%unseen%& option)"
18728 Setting the &%unseen%& option has a similar effect to the &%unseen%& command
18729 qualifier in filter files. It can be used to cause copies of messages to be
18730 delivered to some other destination, while also carrying out a normal delivery.
18731 In effect, the current address is made into a &"parent"& that has two children
18732 &-- one that is delivered as specified by this router, and a clone that goes on
18733 to be routed further. For this reason, &%unseen%& may not be combined with the
18734 &%one_time%& option in a &(redirect)& router.
18736 &*Warning*&: Header lines added to the address (or specified for removal) by
18737 this router or by previous routers affect the &"unseen"& copy of the message
18738 only. The clone that continues to be processed by further routers starts with
18739 no added headers and none specified for removal. For a &%redirect%& router, if
18740 a generated address is the same as the incoming address, this can lead to
18741 duplicate addresses with different header modifications. Exim does not do
18742 duplicate deliveries (except, in certain circumstances, to pipes -- see section
18743 &<<SECTdupaddr>>&), but it is undefined which of the duplicates is discarded,
18744 so this ambiguous situation should be avoided. The &%repeat_use%& option of the
18745 &%redirect%& router may be of help.
18747 Unlike the handling of header modifications, any data that was set by the
18748 &%address_data%& option in the current or previous routers &'is'& passed on to
18749 subsequent routers.
18752 .option user routers string&!! "see below"
18753 .cindex "uid (user id)" "local delivery"
18754 .cindex "local transports" "uid and gid"
18755 .cindex "transport" "local"
18756 .cindex "router" "user for filter processing"
18757 .cindex "filter" "user for processing"
18758 When a router queues an address for a transport, and the transport does not
18759 specify a user, the user given here is used when running the delivery process.
18760 The user may be specified numerically or by name. If expansion fails, the
18761 error is logged and delivery is deferred.
18762 This user is also used by the &(redirect)& router when running a filter file.
18763 The default is unset, except when &%check_local_user%& is set. In this case,
18764 the default is taken from the password information. If the user is specified as
18765 a name, and &%group%& is not set, the group associated with the user is used.
18766 See also &%initgroups%& and &%group%& and the discussion in chapter
18767 &<<CHAPenvironment>>&.
18771 .option verify routers&!? boolean true
18772 Setting this option has the effect of setting &%verify_sender%& and
18773 &%verify_recipient%& to the same value.
18776 .option verify_only routers&!? boolean false
18777 .cindex "EXPN" "with &%verify_only%&"
18779 .cindex "router" "used only when verifying"
18780 If this option is set, the router is used only when verifying an address,
18781 delivering in cutthrough mode or
18782 testing with the &%-bv%& option, not when actually doing a delivery, testing
18783 with the &%-bt%& option, or running the SMTP EXPN command. It can be further
18784 restricted to verifying only senders or recipients by means of
18785 &%verify_sender%& and &%verify_recipient%&.
18787 &*Warning*&: When the router is being run to verify addresses for an incoming
18788 SMTP message, Exim is not running as root, but under its own uid. If the router
18789 accesses any files, you need to make sure that they are accessible to the Exim
18793 .option verify_recipient routers&!? boolean true
18794 If this option is false, the router is skipped when verifying recipient
18796 delivering in cutthrough mode
18797 or testing recipient verification using &%-bv%&.
18798 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18800 See also the &$verify_mode$& variable.
18803 .option verify_sender routers&!? boolean true
18804 If this option is false, the router is skipped when verifying sender addresses
18805 or testing sender verification using &%-bvs%&.
18806 See section &<<SECTrouprecon>>& for a list of the order in which preconditions
18808 See also the &$verify_mode$& variable.
18809 .ecindex IIDgenoprou1
18810 .ecindex IIDgenoprou2
18817 . ////////////////////////////////////////////////////////////////////////////
18818 . ////////////////////////////////////////////////////////////////////////////
18820 .chapter "The accept router" "CHID4"
18821 .cindex "&(accept)& router"
18822 .cindex "routers" "&(accept)&"
18823 The &(accept)& router has no private options of its own. Unless it is being
18824 used purely for verification (see &%verify_only%&) a transport is required to
18825 be defined by the generic &%transport%& option. If the preconditions that are
18826 specified by generic options are met, the router accepts the address and queues
18827 it for the given transport. The most common use of this router is for setting
18828 up deliveries to local mailboxes. For example:
18832 domains = mydomain.example
18834 transport = local_delivery
18836 The &%domains%& condition in this example checks the domain of the address, and
18837 &%check_local_user%& checks that the local part is the login of a local user.
18838 When both preconditions are met, the &(accept)& router runs, and queues the
18839 address for the &(local_delivery)& transport.
18846 . ////////////////////////////////////////////////////////////////////////////
18847 . ////////////////////////////////////////////////////////////////////////////
18849 .chapter "The dnslookup router" "CHAPdnslookup"
18850 .scindex IIDdnsrou1 "&(dnslookup)& router"
18851 .scindex IIDdnsrou2 "routers" "&(dnslookup)&"
18852 The &(dnslookup)& router looks up the hosts that handle mail for the
18853 recipient's domain in the DNS. A transport must always be set for this router,
18854 unless &%verify_only%& is set.
18856 If SRV support is configured (see &%check_srv%& below), Exim first searches for
18857 SRV records. If none are found, or if SRV support is not configured,
18858 MX records are looked up. If no MX records exist, address records are sought.
18859 However, &%mx_domains%& can be set to disable the direct use of address
18862 MX records of equal priority are sorted by Exim into a random order. Exim then
18863 looks for address records for the host names obtained from MX or SRV records.
18864 When a host has more than one IP address, they are sorted into a random order,
18865 except that IPv6 addresses are sorted before IPv4 addresses. If all the
18866 IP addresses found are discarded by a setting of the &%ignore_target_hosts%&
18867 generic option, the router declines.
18869 Unless they have the highest priority (lowest MX value), MX records that point
18870 to the local host, or to any host name that matches &%hosts_treat_as_local%&,
18871 are discarded, together with any other MX records of equal or lower priority.
18873 .cindex "MX record" "pointing to local host"
18874 .cindex "local host" "MX pointing to"
18875 .oindex "&%self%&" "in &(dnslookup)& router"
18876 If the host pointed to by the highest priority MX record, or looked up as an
18877 address record, is the local host, or matches &%hosts_treat_as_local%&, what
18878 happens is controlled by the generic &%self%& option.
18881 .section "Problems with DNS lookups" "SECTprowitdnsloo"
18882 There have been problems with DNS servers when SRV records are looked up.
18883 Some misbehaving servers return a DNS error or timeout when a non-existent
18884 SRV record is sought. Similar problems have in the past been reported for
18885 MX records. The global &%dns_again_means_nonexist%& option can help with this
18886 problem, but it is heavy-handed because it is a global option.
18888 For this reason, there are two options, &%srv_fail_domains%& and
18889 &%mx_fail_domains%&, that control what happens when a DNS lookup in a
18890 &(dnslookup)& router results in a DNS failure or a &"try again"& response. If
18891 an attempt to look up an SRV or MX record causes one of these results, and the
18892 domain matches the relevant list, Exim behaves as if the DNS had responded &"no
18893 such record"&. In the case of an SRV lookup, this means that the router
18894 proceeds to look for MX records; in the case of an MX lookup, it proceeds to
18895 look for A or AAAA records, unless the domain matches &%mx_domains%&, in which
18896 case routing fails.
18899 .section "Declining addresses by dnslookup" "SECTdnslookupdecline"
18900 .cindex "&(dnslookup)& router" "declines"
18901 There are a few cases where a &(dnslookup)& router will decline to accept
18902 an address; if such a router is expected to handle "all remaining non-local
18903 domains", then it is important to set &%no_more%&.
18905 The router will defer rather than decline if the domain
18906 is found in the &%fail_defer_domains%& router option.
18908 Reasons for a &(dnslookup)& router to decline currently include:
18910 The domain does not exist in DNS
18912 The domain exists but the MX record's host part is just "."; this is a common
18913 convention (borrowed from SRV) used to indicate that there is no such service
18914 for this domain and to not fall back to trying A/AAAA records.
18916 Ditto, but for SRV records, when &%check_srv%& is set on this router.
18918 MX record points to a non-existent host.
18920 MX record points to an IP address and the main section option
18921 &%allow_mx_to_ip%& is not set.
18923 MX records exist and point to valid hosts, but all hosts resolve only to
18924 addresses blocked by the &%ignore_target_hosts%& generic option on this router.
18926 The domain is not syntactically valid (see also &%allow_utf8_domains%& and
18927 &%dns_check_names_pattern%& for handling one variant of this)
18929 &%check_secondary_mx%& is set on this router but the local host can
18930 not be found in the MX records (see below)
18936 .section "Private options for dnslookup" "SECID118"
18937 .cindex "options" "&(dnslookup)& router"
18938 The private options for the &(dnslookup)& router are as follows:
18940 .option check_secondary_mx dnslookup boolean false
18941 .cindex "MX record" "checking for secondary"
18942 If this option is set, the router declines unless the local host is found in
18943 (and removed from) the list of hosts obtained by MX lookup. This can be used to
18944 process domains for which the local host is a secondary mail exchanger
18945 differently to other domains. The way in which Exim decides whether a host is
18946 the local host is described in section &<<SECTreclocipadd>>&.
18949 .option check_srv dnslookup string&!! unset
18950 .cindex "SRV record" "enabling use of"
18951 The &(dnslookup)& router supports the use of SRV records (see RFC 2782) in
18952 addition to MX and address records. The support is disabled by default. To
18953 enable SRV support, set the &%check_srv%& option to the name of the service
18954 required. For example,
18958 looks for SRV records that refer to the normal smtp service. The option is
18959 expanded, so the service name can vary from message to message or address
18960 to address. This might be helpful if SRV records are being used for a
18961 submission service. If the expansion is forced to fail, the &%check_srv%&
18962 option is ignored, and the router proceeds to look for MX records in the
18965 When the expansion succeeds, the router searches first for SRV records for
18966 the given service (it assumes TCP protocol). A single SRV record with a
18967 host name that consists of just a single dot indicates &"no such service for
18968 this domain"&; if this is encountered, the router declines. If other kinds of
18969 SRV record are found, they are used to construct a host list for delivery
18970 according to the rules of RFC 2782. MX records are not sought in this case.
18972 When no SRV records are found, MX records (and address records) are sought in
18973 the traditional way. In other words, SRV records take precedence over MX
18974 records, just as MX records take precedence over address records. Note that
18975 this behaviour is not sanctioned by RFC 2782, though a previous draft RFC
18976 defined it. It is apparently believed that MX records are sufficient for email
18977 and that SRV records should not be used for this purpose. However, SRV records
18978 have an additional &"weight"& feature which some people might find useful when
18979 trying to split an SMTP load between hosts of different power.
18981 See section &<<SECTprowitdnsloo>>& above for a discussion of Exim's behaviour
18982 when there is a DNS lookup error.
18987 .option fail_defer_domains dnslookup "domain list&!!" unset
18988 .cindex "MX record" "not found"
18989 DNS lookups for domains matching &%fail_defer_domains%&
18990 which find no matching record will cause the router to defer
18991 rather than the default behaviour of decline.
18992 This maybe be useful for queueing messages for a newly created
18993 domain while the DNS configuration is not ready.
18994 However, it will result in any message with mistyped domains
18998 .option ipv4_only "string&!!" unset
18999 .cindex IPv6 disabling
19000 .cindex DNS "IPv6 disabling"
19001 The string is expanded, and if the result is anything but a forced failure,
19002 or an empty string, or one of the strings “0” or “no” or “false”
19003 (checked without regard to the case of the letters),
19004 only A records are used.
19006 .option ipv4_prefer "string&!!" unset
19007 .cindex IPv4 preference
19008 .cindex DNS "IPv4 preference"
19009 The string is expanded, and if the result is anything but a forced failure,
19010 or an empty string, or one of the strings “0” or “no” or “false”
19011 (checked without regard to the case of the letters),
19012 A records are sorted before AAAA records (inverting the default).
19014 .option mx_domains dnslookup "domain list&!!" unset
19015 .cindex "MX record" "required to exist"
19016 .cindex "SRV record" "required to exist"
19017 A domain that matches &%mx_domains%& is required to have either an MX or an SRV
19018 record in order to be recognized. (The name of this option could be improved.)
19019 For example, if all the mail hosts in &'fict.example'& are known to have MX
19020 records, except for those in &'discworld.fict.example'&, you could use this
19023 mx_domains = ! *.discworld.fict.example : *.fict.example
19025 This specifies that messages addressed to a domain that matches the list but
19026 has no MX record should be bounced immediately instead of being routed using
19027 the address record.
19030 .option mx_fail_domains dnslookup "domain list&!!" unset
19031 If the DNS lookup for MX records for one of the domains in this list causes a
19032 DNS lookup error, Exim behaves as if no MX records were found. See section
19033 &<<SECTprowitdnsloo>>& for more discussion.
19038 .option qualify_single dnslookup boolean true
19039 .cindex "DNS" "resolver options"
19040 .cindex "DNS" "qualifying single-component names"
19041 When this option is true, the resolver option RES_DEFNAMES is set for DNS
19042 lookups. Typically, but not standardly, this causes the resolver to qualify
19043 single-component names with the default domain. For example, on a machine
19044 called &'dictionary.ref.example'&, the domain &'thesaurus'& would be changed to
19045 &'thesaurus.ref.example'& inside the resolver. For details of what your
19046 resolver actually does, consult your man pages for &'resolver'& and
19051 .option rewrite_headers dnslookup boolean true
19052 .cindex "rewriting" "header lines"
19053 .cindex "header lines" "rewriting"
19054 If the domain name in the address that is being processed is not fully
19055 qualified, it may be expanded to its full form by a DNS lookup. For example, if
19056 an address is specified as &'dormouse@teaparty'&, the domain might be
19057 expanded to &'teaparty.wonderland.fict.example'&. Domain expansion can also
19058 occur as a result of setting the &%widen_domains%& option. If
19059 &%rewrite_headers%& is true, all occurrences of the abbreviated domain name in
19060 any &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-to:'&, &'Sender:'&, and &'To:'&
19061 header lines of the message are rewritten with the full domain name.
19063 This option should be turned off only when it is known that no message is
19064 ever going to be sent outside an environment where the abbreviation makes
19067 When an MX record is looked up in the DNS and matches a wildcard record, name
19068 servers normally return a record containing the name that has been looked up,
19069 making it impossible to detect whether a wildcard was present or not. However,
19070 some name servers have recently been seen to return the wildcard entry. If the
19071 name returned by a DNS lookup begins with an asterisk, it is not used for
19075 .option same_domain_copy_routing dnslookup boolean false
19076 .cindex "address" "copying routing"
19077 Addresses with the same domain are normally routed by the &(dnslookup)& router
19078 to the same list of hosts. However, this cannot be presumed, because the router
19079 options and preconditions may refer to the local part of the address. By
19080 default, therefore, Exim routes each address in a message independently. DNS
19081 servers run caches, so repeated DNS lookups are not normally expensive, and in
19082 any case, personal messages rarely have more than a few recipients.
19084 If you are running mailing lists with large numbers of subscribers at the same
19085 domain, and you are using a &(dnslookup)& router which is independent of the
19086 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
19087 lookups for identical domains in one message. In this case, when &(dnslookup)&
19088 routes an address to a remote transport, any other unrouted addresses in the
19089 message that have the same domain are automatically given the same routing
19090 without processing them independently,
19091 provided the following conditions are met:
19094 No router that processed the address specified &%headers_add%& or
19095 &%headers_remove%&.
19097 The router did not change the address in any way, for example, by &"widening"&
19104 .option search_parents dnslookup boolean false
19105 .cindex "DNS" "resolver options"
19106 When this option is true, the resolver option RES_DNSRCH is set for DNS
19107 lookups. This is different from the &%qualify_single%& option in that it
19108 applies to domains containing dots. Typically, but not standardly, it causes
19109 the resolver to search for the name in the current domain and in parent
19110 domains. For example, on a machine in the &'fict.example'& domain, if looking
19111 up &'teaparty.wonderland'& failed, the resolver would try
19112 &'teaparty.wonderland.fict.example'&. For details of what your resolver
19113 actually does, consult your man pages for &'resolver'& and &'resolv.conf'&.
19115 Setting this option true can cause problems in domains that have a wildcard MX
19116 record, because any domain that does not have its own MX record matches the
19121 .option srv_fail_domains dnslookup "domain list&!!" unset
19122 If the DNS lookup for SRV records for one of the domains in this list causes a
19123 DNS lookup error, Exim behaves as if no SRV records were found. See section
19124 &<<SECTprowitdnsloo>>& for more discussion.
19129 .option widen_domains dnslookup "string list" unset
19130 .cindex "domain" "partial; widening"
19131 If a DNS lookup fails and this option is set, each of its strings in turn is
19132 added onto the end of the domain, and the lookup is tried again. For example,
19135 widen_domains = fict.example:ref.example
19137 is set and a lookup of &'klingon.dictionary'& fails,
19138 &'klingon.dictionary.fict.example'& is looked up, and if this fails,
19139 &'klingon.dictionary.ref.example'& is tried. Note that the &%qualify_single%&
19140 and &%search_parents%& options can cause some widening to be undertaken inside
19141 the DNS resolver. &%widen_domains%& is not applied to sender addresses
19142 when verifying, unless &%rewrite_headers%& is false (not the default).
19145 .section "Effect of qualify_single and search_parents" "SECID119"
19146 When a domain from an envelope recipient is changed by the resolver as a result
19147 of the &%qualify_single%& or &%search_parents%& options, Exim rewrites the
19148 corresponding address in the message's header lines unless &%rewrite_headers%&
19149 is set false. Exim then re-routes the address, using the full domain.
19151 These two options affect only the DNS lookup that takes place inside the router
19152 for the domain of the address that is being routed. They do not affect lookups
19153 such as that implied by
19157 that may happen while processing a router precondition before the router is
19158 entered. No widening ever takes place for these lookups.
19159 .ecindex IIDdnsrou1
19160 .ecindex IIDdnsrou2
19170 . ////////////////////////////////////////////////////////////////////////////
19171 . ////////////////////////////////////////////////////////////////////////////
19173 .chapter "The ipliteral router" "CHID5"
19174 .cindex "&(ipliteral)& router"
19175 .cindex "domain literal" "routing"
19176 .cindex "routers" "&(ipliteral)&"
19177 This router has no private options. Unless it is being used purely for
19178 verification (see &%verify_only%&) a transport is required to be defined by the
19179 generic &%transport%& option. The router accepts the address if its domain part
19180 takes the form of an RFC 2822 domain literal. For example, the &(ipliteral)&
19181 router handles the address
19185 by setting up delivery to the host with that IP address. IPv4 domain literals
19186 consist of an IPv4 address enclosed in square brackets. IPv6 domain literals
19187 are similar, but the address is preceded by &`ipv6:`&. For example:
19189 postmaster@[ipv6:fe80::a00:20ff:fe86:a061.5678]
19191 Exim allows &`ipv4:`& before IPv4 addresses, for consistency, and on the
19192 grounds that sooner or later somebody will try it.
19194 .oindex "&%self%&" "in &(ipliteral)& router"
19195 If the IP address matches something in &%ignore_target_hosts%&, the router
19196 declines. If an IP literal turns out to refer to the local host, the generic
19197 &%self%& option determines what happens.
19199 The RFCs require support for domain literals; however, their use is
19200 controversial in today's Internet. If you want to use this router, you must
19201 also set the main configuration option &%allow_domain_literals%&. Otherwise,
19202 Exim will not recognize the domain literal syntax in addresses.
19206 . ////////////////////////////////////////////////////////////////////////////
19207 . ////////////////////////////////////////////////////////////////////////////
19209 .chapter "The iplookup router" "CHID6"
19210 .cindex "&(iplookup)& router"
19211 .cindex "routers" "&(iplookup)&"
19212 The &(iplookup)& router was written to fulfil a specific requirement in
19213 Cambridge University (which in fact no longer exists). For this reason, it is
19214 not included in the binary of Exim by default. If you want to include it, you
19217 ROUTER_IPLOOKUP=yes
19219 in your &_Local/Makefile_& configuration file.
19221 The &(iplookup)& router routes an address by sending it over a TCP or UDP
19222 connection to one or more specific hosts. The host can then return the same or
19223 a different address &-- in effect rewriting the recipient address in the
19224 message's envelope. The new address is then passed on to subsequent routers. If
19225 this process fails, the address can be passed on to other routers, or delivery
19226 can be deferred. Since &(iplookup)& is just a rewriting router, a transport
19227 must not be specified for it.
19229 .cindex "options" "&(iplookup)& router"
19230 .option hosts iplookup string unset
19231 This option must be supplied. Its value is a colon-separated list of host
19232 names. The hosts are looked up using &[gethostbyname()]&
19233 (or &[getipnodebyname()]& when available)
19234 and are tried in order until one responds to the query. If none respond, what
19235 happens is controlled by &%optional%&.
19238 .option optional iplookup boolean false
19239 If &%optional%& is true, if no response is obtained from any host, the address
19240 is passed to the next router, overriding &%no_more%&. If &%optional%& is false,
19241 delivery to the address is deferred.
19244 .option port iplookup integer 0
19245 .cindex "port" "&(iplookup)& router"
19246 This option must be supplied. It specifies the port number for the TCP or UDP
19250 .option protocol iplookup string udp
19251 This option can be set to &"udp"& or &"tcp"& to specify which of the two
19252 protocols is to be used.
19255 .option query iplookup string&!! "see below"
19256 This defines the content of the query that is sent to the remote hosts. The
19259 $local_part@$domain $local_part@$domain
19261 The repetition serves as a way of checking that a response is to the correct
19262 query in the default case (see &%response_pattern%& below).
19265 .option reroute iplookup string&!! unset
19266 If this option is not set, the rerouted address is precisely the byte string
19267 returned by the remote host, up to the first white space, if any. If set, the
19268 string is expanded to form the rerouted address. It can include parts matched
19269 in the response by &%response_pattern%& by means of numeric variables such as
19270 &$1$&, &$2$&, etc. The variable &$0$& refers to the entire input string,
19271 whether or not a pattern is in use. In all cases, the rerouted address must end
19272 up in the form &'local_part@domain'&.
19275 .option response_pattern iplookup string unset
19276 This option can be set to a regular expression that is applied to the string
19277 returned from the remote host. If the pattern does not match the response, the
19278 router declines. If &%response_pattern%& is not set, no checking of the
19279 response is done, unless the query was defaulted, in which case there is a
19280 check that the text returned after the first white space is the original
19281 address. This checks that the answer that has been received is in response to
19282 the correct question. For example, if the response is just a new domain, the
19283 following could be used:
19285 response_pattern = ^([^@]+)$
19286 reroute = $local_part@$1
19289 .option timeout iplookup time 5s
19290 This specifies the amount of time to wait for a response from the remote
19291 machine. The same timeout is used for the &[connect()]& function for a TCP
19292 call. It does not apply to UDP.
19297 . ////////////////////////////////////////////////////////////////////////////
19298 . ////////////////////////////////////////////////////////////////////////////
19300 .chapter "The manualroute router" "CHID7"
19301 .scindex IIDmanrou1 "&(manualroute)& router"
19302 .scindex IIDmanrou2 "routers" "&(manualroute)&"
19303 .cindex "domain" "manually routing"
19304 The &(manualroute)& router is so-called because it provides a way of manually
19305 routing an address according to its domain. It is mainly used when you want to
19306 route addresses to remote hosts according to your own rules, bypassing the
19307 normal DNS routing that looks up MX records. However, &(manualroute)& can also
19308 route to local transports, a facility that may be useful if you want to save
19309 messages for dial-in hosts in local files.
19311 The &(manualroute)& router compares a list of domain patterns with the domain
19312 it is trying to route. If there is no match, the router declines. Each pattern
19313 has associated with it a list of hosts and some other optional data, which may
19314 include a transport. The combination of a pattern and its data is called a
19315 &"routing rule"&. For patterns that do not have an associated transport, the
19316 generic &%transport%& option must specify a transport, unless the router is
19317 being used purely for verification (see &%verify_only%&).
19320 In the case of verification, matching the domain pattern is sufficient for the
19321 router to accept the address. When actually routing an address for delivery,
19322 an address that matches a domain pattern is queued for the associated
19323 transport. If the transport is not a local one, a host list must be associated
19324 with the pattern; IP addresses are looked up for the hosts, and these are
19325 passed to the transport along with the mail address. For local transports, a
19326 host list is optional. If it is present, it is passed in &$host$& as a single
19329 The list of routing rules can be provided as an inline string in
19330 &%route_list%&, or the data can be obtained by looking up the domain in a file
19331 or database by setting &%route_data%&. Only one of these settings may appear in
19332 any one instance of &(manualroute)&. The format of routing rules is described
19333 below, following the list of private options.
19336 .section "Private options for manualroute" "SECTprioptman"
19338 .cindex "options" "&(manualroute)& router"
19339 The private options for the &(manualroute)& router are as follows:
19341 .option host_all_ignored manualroute string defer
19342 See &%host_find_failed%&.
19344 .option host_find_failed manualroute string freeze
19345 This option controls what happens when &(manualroute)& tries to find an IP
19346 address for a host, and the host does not exist. The option can be set to one
19347 of the following values:
19356 The default (&"freeze"&) assumes that this state is a serious configuration
19357 error. The difference between &"pass"& and &"decline"& is that the former
19358 forces the address to be passed to the next router (or the router defined by
19361 overriding &%no_more%&, whereas the latter passes the address to the next
19362 router only if &%more%& is true.
19364 The value &"ignore"& causes Exim to completely ignore a host whose IP address
19365 cannot be found. If all the hosts in the list are ignored, the behaviour is
19366 controlled by the &%host_all_ignored%& option. This takes the same values
19367 as &%host_find_failed%&, except that it cannot be set to &"ignore"&.
19369 The &%host_find_failed%& option applies only to a definite &"does not exist"&
19370 state; if a host lookup gets a temporary error, delivery is deferred unless the
19371 generic &%pass_on_timeout%& option is set.
19374 .option hosts_randomize manualroute boolean false
19375 .cindex "randomized host list"
19376 .cindex "host" "list of; randomized"
19377 If this option is set, the order of the items in a host list in a routing rule
19378 is randomized each time the list is used, unless an option in the routing rule
19379 overrides (see below). Randomizing the order of a host list can be used to do
19380 crude load sharing. However, if more than one mail address is routed by the
19381 same router to the same host list, the host lists are considered to be the same
19382 (even though they may be randomized into different orders) for the purpose of
19383 deciding whether to batch the deliveries into a single SMTP transaction.
19385 When &%hosts_randomize%& is true, a host list may be split
19386 into groups whose order is separately randomized. This makes it possible to
19387 set up MX-like behaviour. The boundaries between groups are indicated by an
19388 item that is just &`+`& in the host list. For example:
19390 route_list = * host1:host2:host3:+:host4:host5
19392 The order of the first three hosts and the order of the last two hosts is
19393 randomized for each use, but the first three always end up before the last two.
19394 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored. If a
19395 randomized host list is passed to an &(smtp)& transport that also has
19396 &%hosts_randomize set%&, the list is not re-randomized.
19399 .option route_data manualroute string&!! unset
19400 If this option is set, it must expand to yield the data part of a routing rule.
19401 Typically, the expansion string includes a lookup based on the domain. For
19404 route_data = ${lookup{$domain}dbm{/etc/routes}}
19406 If the expansion is forced to fail, or the result is an empty string, the
19407 router declines. Other kinds of expansion failure cause delivery to be
19411 .option route_list manualroute "string list" unset
19412 This string is a list of routing rules, in the form defined below. Note that,
19413 unlike most string lists, the items are separated by semicolons. This is so
19414 that they may contain colon-separated host lists.
19417 .option same_domain_copy_routing manualroute boolean false
19418 .cindex "address" "copying routing"
19419 Addresses with the same domain are normally routed by the &(manualroute)&
19420 router to the same list of hosts. However, this cannot be presumed, because the
19421 router options and preconditions may refer to the local part of the address. By
19422 default, therefore, Exim routes each address in a message independently. DNS
19423 servers run caches, so repeated DNS lookups are not normally expensive, and in
19424 any case, personal messages rarely have more than a few recipients.
19426 If you are running mailing lists with large numbers of subscribers at the same
19427 domain, and you are using a &(manualroute)& router which is independent of the
19428 local part, you can set &%same_domain_copy_routing%& to bypass repeated DNS
19429 lookups for identical domains in one message. In this case, when
19430 &(manualroute)& routes an address to a remote transport, any other unrouted
19431 addresses in the message that have the same domain are automatically given the
19432 same routing without processing them independently. However, this is only done
19433 if &%headers_add%& and &%headers_remove%& are unset.
19438 .section "Routing rules in route_list" "SECID120"
19439 The value of &%route_list%& is a string consisting of a sequence of routing
19440 rules, separated by semicolons. If a semicolon is needed in a rule, it can be
19441 entered as two semicolons. Alternatively, the list separator can be changed as
19442 described (for colon-separated lists) in section &<<SECTlistconstruct>>&.
19443 Empty rules are ignored. The format of each rule is
19445 <&'domain pattern'&> <&'list of hosts'&> <&'options'&>
19447 The following example contains two rules, each with a simple domain pattern and
19451 dict.ref.example mail-1.ref.example:mail-2.ref.example ; \
19452 thes.ref.example mail-3.ref.example:mail-4.ref.example
19454 The three parts of a rule are separated by white space. The pattern and the
19455 list of hosts can be enclosed in quotes if necessary, and if they are, the
19456 usual quoting rules apply. Each rule in a &%route_list%& must start with a
19457 single domain pattern, which is the only mandatory item in the rule. The
19458 pattern is in the same format as one item in a domain list (see section
19459 &<<SECTdomainlist>>&),
19460 except that it may not be the name of an interpolated file.
19461 That is, it may be wildcarded, or a regular expression, or a file or database
19462 lookup (with semicolons doubled, because of the use of semicolon as a separator
19463 in a &%route_list%&).
19465 The rules in &%route_list%& are searched in order until one of the patterns
19466 matches the domain that is being routed. The list of hosts and then options are
19467 then used as described below. If there is no match, the router declines. When
19468 &%route_list%& is set, &%route_data%& must not be set.
19472 .section "Routing rules in route_data" "SECID121"
19473 The use of &%route_list%& is convenient when there are only a small number of
19474 routing rules. For larger numbers, it is easier to use a file or database to
19475 hold the routing information, and use the &%route_data%& option instead.
19476 The value of &%route_data%& is a list of hosts, followed by (optional) options.
19477 Most commonly, &%route_data%& is set as a string that contains an
19478 expansion lookup. For example, suppose we place two routing rules in a file
19481 dict.ref.example: mail-1.ref.example:mail-2.ref.example
19482 thes.ref.example: mail-3.ref.example:mail-4.ref.example
19484 This data can be accessed by setting
19486 route_data = ${lookup{$domain}lsearch{/the/file/name}}
19488 Failure of the lookup results in an empty string, causing the router to
19489 decline. However, you do not have to use a lookup in &%route_data%&. The only
19490 requirement is that the result of expanding the string is a list of hosts,
19491 possibly followed by options, separated by white space. The list of hosts must
19492 be enclosed in quotes if it contains white space.
19497 .section "Format of the list of hosts" "SECID122"
19498 A list of hosts, whether obtained via &%route_data%& or &%route_list%&, is
19499 always separately expanded before use. If the expansion fails, the router
19500 declines. The result of the expansion must be a colon-separated list of names
19501 and/or IP addresses, optionally also including ports. The format of each item
19502 in the list is described in the next section. The list separator can be changed
19503 as described in section &<<SECTlistconstruct>>&.
19505 If the list of hosts was obtained from a &%route_list%& item, the following
19506 variables are set during its expansion:
19509 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(manualroute)& router"
19510 If the domain was matched against a regular expression, the numeric variables
19511 &$1$&, &$2$&, etc. may be set. For example:
19513 route_list = ^domain(\d+) host-$1.text.example
19516 &$0$& is always set to the entire domain.
19518 &$1$& is also set when partial matching is done in a file lookup.
19521 .vindex "&$value$&"
19522 If the pattern that matched the domain was a lookup item, the data that was
19523 looked up is available in the expansion variable &$value$&. For example:
19525 route_list = lsearch;;/some/file.routes $value
19529 Note the doubling of the semicolon in the pattern that is necessary because
19530 semicolon is the default route list separator.
19534 .section "Format of one host item" "SECTformatonehostitem"
19535 Each item in the list of hosts is either a host name or an IP address,
19536 optionally with an attached port number. When no port is given, an IP address
19537 is not enclosed in brackets. When a port is specified, it overrides the port
19538 specification on the transport. The port is separated from the name or address
19539 by a colon. This leads to some complications:
19542 Because colon is the default separator for the list of hosts, either
19543 the colon that specifies a port must be doubled, or the list separator must
19544 be changed. The following two examples have the same effect:
19546 route_list = * "host1.tld::1225 : host2.tld::1226"
19547 route_list = * "<+ host1.tld:1225 + host2.tld:1226"
19550 When IPv6 addresses are involved, it gets worse, because they contain
19551 colons of their own. To make this case easier, it is permitted to
19552 enclose an IP address (either v4 or v6) in square brackets if a port
19553 number follows. For example:
19555 route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
19559 .section "How the list of hosts is used" "SECThostshowused"
19560 When an address is routed to an &(smtp)& transport by &(manualroute)&, each of
19561 the hosts is tried, in the order specified, when carrying out the SMTP
19562 delivery. However, the order can be changed by setting the &%hosts_randomize%&
19563 option, either on the router (see section &<<SECTprioptman>>& above), or on the
19566 Hosts may be listed by name or by IP address. An unadorned name in the list of
19567 hosts is interpreted as a host name. A name that is followed by &`/MX`& is
19568 interpreted as an indirection to a sublist of hosts obtained by looking up MX
19569 records in the DNS. For example:
19571 route_list = * x.y.z:p.q.r/MX:e.f.g
19573 If this feature is used with a port specifier, the port must come last. For
19576 route_list = * dom1.tld/mx::1225
19578 If the &%hosts_randomize%& option is set, the order of the items in the list is
19579 randomized before any lookups are done. Exim then scans the list; for any name
19580 that is not followed by &`/MX`& it looks up an IP address. If this turns out to
19581 be an interface on the local host and the item is not the first in the list,
19582 Exim discards it and any subsequent items. If it is the first item, what
19583 happens is controlled by the
19584 .oindex "&%self%&" "in &(manualroute)& router"
19585 &%self%& option of the router.
19587 A name on the list that is followed by &`/MX`& is replaced with the list of
19588 hosts obtained by looking up MX records for the name. This is always a DNS
19589 lookup; the &%bydns%& and &%byname%& options (see section &<<SECThowoptused>>&
19590 below) are not relevant here. The order of these hosts is determined by the
19591 preference values in the MX records, according to the usual rules. Because
19592 randomizing happens before the MX lookup, it does not affect the order that is
19593 defined by MX preferences.
19595 If the local host is present in the sublist obtained from MX records, but is
19596 not the most preferred host in that list, it and any equally or less
19597 preferred hosts are removed before the sublist is inserted into the main list.
19599 If the local host is the most preferred host in the MX list, what happens
19600 depends on where in the original list of hosts the &`/MX`& item appears. If it
19601 is not the first item (that is, there are previous hosts in the main list),
19602 Exim discards this name and any subsequent items in the main list.
19604 If the MX item is first in the list of hosts, and the local host is the
19605 most preferred host, what happens is controlled by the &%self%& option of the
19608 DNS failures when lookup up the MX records are treated in the same way as DNS
19609 failures when looking up IP addresses: &%pass_on_timeout%& and
19610 &%host_find_failed%& are used when relevant.
19612 The generic &%ignore_target_hosts%& option applies to all hosts in the list,
19613 whether obtained from an MX lookup or not.
19617 .section "How the options are used" "SECThowoptused"
19618 The options are a sequence of words, space-separated.
19619 One of the words can be the name of a transport; this overrides the
19620 &%transport%& option on the router for this particular routing rule only. The
19621 other words (if present) control randomization of the list of hosts on a
19622 per-rule basis, and how the IP addresses of the hosts are to be found when
19623 routing to a remote transport. These options are as follows:
19626 &%randomize%&: randomize the order of the hosts in this list, overriding the
19627 setting of &%hosts_randomize%& for this routing rule only.
19629 &%no_randomize%&: do not randomize the order of the hosts in this list,
19630 overriding the setting of &%hosts_randomize%& for this routing rule only.
19632 &%byname%&: use &[getipnodebyname()]& (&[gethostbyname()]& on older systems) to
19633 find IP addresses. This function may ultimately cause a DNS lookup, but it may
19634 also look in &_/etc/hosts_& or other sources of information.
19636 &%bydns%&: look up address records for the hosts directly in the DNS; fail if
19637 no address records are found. If there is a temporary DNS error (such as a
19638 timeout), delivery is deferred.
19640 &%ipv4_only%&: in direct DNS lookups, look up only A records.
19642 &%ipv4_prefer%&: in direct DNS lookups, sort A records before AAAA records.
19647 route_list = domain1 host1:host2:host3 randomize bydns;\
19648 domain2 host4:host5
19650 If neither &%byname%& nor &%bydns%& is given, Exim behaves as follows: First, a
19651 DNS lookup is done. If this yields anything other than HOST_NOT_FOUND, that
19652 result is used. Otherwise, Exim goes on to try a call to &[getipnodebyname()]&
19653 or &[gethostbyname()]&, and the result of the lookup is the result of that
19656 &*Warning*&: It has been discovered that on some systems, if a DNS lookup
19657 called via &[getipnodebyname()]& times out, HOST_NOT_FOUND is returned
19658 instead of TRY_AGAIN. That is why the default action is to try a DNS
19659 lookup first. Only if that gives a definite &"no such host"& is the local
19662 &*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
19663 inadvertent constraint that a transport name as an option had to be the last
19668 If no IP address for a host can be found, what happens is controlled by the
19669 &%host_find_failed%& option.
19672 When an address is routed to a local transport, IP addresses are not looked up.
19673 The host list is passed to the transport in the &$host$& variable.
19677 .section "Manualroute examples" "SECID123"
19678 In some of the examples that follow, the presence of the &%remote_smtp%&
19679 transport, as defined in the default configuration file, is assumed:
19682 .cindex "smart host" "example router"
19683 The &(manualroute)& router can be used to forward all external mail to a
19684 &'smart host'&. If you have set up, in the main part of the configuration, a
19685 named domain list that contains your local domains, for example:
19687 domainlist local_domains = my.domain.example
19689 You can arrange for all other domains to be routed to a smart host by making
19690 your first router something like this:
19693 driver = manualroute
19694 domains = !+local_domains
19695 transport = remote_smtp
19696 route_list = * smarthost.ref.example
19698 This causes all non-local addresses to be sent to the single host
19699 &'smarthost.ref.example'&. If a colon-separated list of smart hosts is given,
19700 they are tried in order
19701 (but you can use &%hosts_randomize%& to vary the order each time).
19702 Another way of configuring the same thing is this:
19705 driver = manualroute
19706 transport = remote_smtp
19707 route_list = !+local_domains smarthost.ref.example
19709 There is no difference in behaviour between these two routers as they stand.
19710 However, they behave differently if &%no_more%& is added to them. In the first
19711 example, the router is skipped if the domain does not match the &%domains%&
19712 precondition; the following router is always tried. If the router runs, it
19713 always matches the domain and so can never decline. Therefore, &%no_more%&
19714 would have no effect. In the second case, the router is never skipped; it
19715 always runs. However, if it doesn't match the domain, it declines. In this case
19716 &%no_more%& would prevent subsequent routers from running.
19719 .cindex "mail hub example"
19720 A &'mail hub'& is a host which receives mail for a number of domains via MX
19721 records in the DNS and delivers it via its own private routing mechanism. Often
19722 the final destinations are behind a firewall, with the mail hub being the one
19723 machine that can connect to machines both inside and outside the firewall. The
19724 &(manualroute)& router is usually used on a mail hub to route incoming messages
19725 to the correct hosts. For a small number of domains, the routing can be inline,
19726 using the &%route_list%& option, but for a larger number a file or database
19727 lookup is easier to manage.
19729 If the domain names are in fact the names of the machines to which the mail is
19730 to be sent by the mail hub, the configuration can be quite simple. For
19734 driver = manualroute
19735 transport = remote_smtp
19736 route_list = *.rhodes.tvs.example $domain
19738 This configuration routes domains that match &`*.rhodes.tvs.example`& to hosts
19739 whose names are the same as the mail domains. A similar approach can be taken
19740 if the host name can be obtained from the domain name by a string manipulation
19741 that the expansion facilities can handle. Otherwise, a lookup based on the
19742 domain can be used to find the host:
19745 driver = manualroute
19746 transport = remote_smtp
19747 route_data = ${lookup {$domain} cdb {/internal/host/routes}}
19749 The result of the lookup must be the name or IP address of the host (or
19750 hosts) to which the address is to be routed. If the lookup fails, the route
19751 data is empty, causing the router to decline. The address then passes to the
19755 .cindex "batched SMTP output example"
19756 .cindex "SMTP" "batched outgoing; example"
19757 You can use &(manualroute)& to deliver messages to pipes or files in batched
19758 SMTP format for onward transportation by some other means. This is one way of
19759 storing mail for a dial-up host when it is not connected. The route list entry
19760 can be as simple as a single domain name in a configuration like this:
19763 driver = manualroute
19764 transport = batchsmtp_appendfile
19765 route_list = saved.domain.example
19767 though often a pattern is used to pick up more than one domain. If there are
19768 several domains or groups of domains with different transport requirements,
19769 different transports can be listed in the routing information:
19772 driver = manualroute
19774 *.saved.domain1.example $domain batch_appendfile; \
19775 *.saved.domain2.example \
19776 ${lookup{$domain}dbm{/domain2/hosts}{$value}fail} \
19779 .vindex "&$domain$&"
19781 The first of these just passes the domain in the &$host$& variable, which
19782 doesn't achieve much (since it is also in &$domain$&), but the second does a
19783 file lookup to find a value to pass, causing the router to decline to handle
19784 the address if the lookup fails.
19787 .cindex "UUCP" "example of router for"
19788 Routing mail directly to UUCP software is a specific case of the use of
19789 &(manualroute)& in a gateway to another mail environment. This is an example of
19790 one way it can be done:
19796 command = /usr/local/bin/uux -r - \
19797 ${substr_-5:$host}!rmail ${local_part}
19798 return_fail_output = true
19803 driver = manualroute
19805 ${lookup{$domain}lsearch{/usr/local/exim/uucphosts}}
19807 The file &_/usr/local/exim/uucphosts_& contains entries like
19809 darksite.ethereal.example: darksite.UUCP
19811 It can be set up more simply without adding and removing &".UUCP"& but this way
19812 makes clear the distinction between the domain name
19813 &'darksite.ethereal.example'& and the UUCP host name &'darksite'&.
19815 .ecindex IIDmanrou1
19816 .ecindex IIDmanrou2
19825 . ////////////////////////////////////////////////////////////////////////////
19826 . ////////////////////////////////////////////////////////////////////////////
19828 .chapter "The queryprogram router" "CHAPdriverlast"
19829 .scindex IIDquerou1 "&(queryprogram)& router"
19830 .scindex IIDquerou2 "routers" "&(queryprogram)&"
19831 .cindex "routing" "by external program"
19832 The &(queryprogram)& router routes an address by running an external command
19833 and acting on its output. This is an expensive way to route, and is intended
19834 mainly for use in lightly-loaded systems, or for performing experiments.
19835 However, if it is possible to use the precondition options (&%domains%&,
19836 &%local_parts%&, etc) to skip this router for most addresses, it could sensibly
19837 be used in special cases, even on a busy host. There are the following private
19839 .cindex "options" "&(queryprogram)& router"
19841 .option command queryprogram string&!! unset
19842 This option must be set. It specifies the command that is to be run. The
19843 command is split up into a command name and arguments, and then each is
19844 expanded separately (exactly as for a &(pipe)& transport, described in chapter
19845 &<<CHAPpipetransport>>&).
19848 .option command_group queryprogram string unset
19849 .cindex "gid (group id)" "in &(queryprogram)& router"
19850 This option specifies a gid to be set when running the command while routing an
19851 address for deliver. It must be set if &%command_user%& specifies a numerical
19852 uid. If it begins with a digit, it is interpreted as the numerical value of the
19853 gid. Otherwise it is looked up using &[getgrnam()]&.
19856 .option command_user queryprogram string unset
19857 .cindex "uid (user id)" "for &(queryprogram)&"
19858 This option must be set. It specifies the uid which is set when running the
19859 command while routing an address for delivery. If the value begins with a digit,
19860 it is interpreted as the numerical value of the uid. Otherwise, it is looked up
19861 using &[getpwnam()]& to obtain a value for the uid and, if &%command_group%& is
19862 not set, a value for the gid also.
19864 &*Warning:*& Changing uid and gid is possible only when Exim is running as
19865 root, which it does during a normal delivery in a conventional configuration.
19866 However, when an address is being verified during message reception, Exim is
19867 usually running as the Exim user, not as root. If the &(queryprogram)& router
19868 is called from a non-root process, Exim cannot change uid or gid before running
19869 the command. In this circumstance the command runs under the current uid and
19873 .option current_directory queryprogram string /
19874 This option specifies an absolute path which is made the current directory
19875 before running the command.
19878 .option timeout queryprogram time 1h
19879 If the command does not complete within the timeout period, its process group
19880 is killed and the message is frozen. A value of zero time specifies no
19884 The standard output of the command is connected to a pipe, which is read when
19885 the command terminates. It should consist of a single line of output,
19886 containing up to five fields, separated by white space. The maximum length of
19887 the line is 1023 characters. Longer lines are silently truncated. The first
19888 field is one of the following words (case-insensitive):
19891 &'Accept'&: routing succeeded; the remaining fields specify what to do (see
19894 &'Decline'&: the router declines; pass the address to the next router, unless
19895 &%no_more%& is set.
19897 &'Fail'&: routing failed; do not pass the address to any more routers. Any
19898 subsequent text on the line is an error message. If the router is run as part
19899 of address verification during an incoming SMTP message, the message is
19900 included in the SMTP response.
19902 &'Defer'&: routing could not be completed at this time; try again later. Any
19903 subsequent text on the line is an error message which is logged. It is not
19904 included in any SMTP response.
19906 &'Freeze'&: the same as &'defer'&, except that the message is frozen.
19908 &'Pass'&: pass the address to the next router (or the router specified by
19909 &%pass_router%&), overriding &%no_more%&.
19911 &'Redirect'&: the message is redirected. The remainder of the line is a list of
19912 new addresses, which are routed independently, starting with the first router,
19913 or the router specified by &%redirect_router%&, if set.
19916 When the first word is &'accept'&, the remainder of the line consists of a
19917 number of keyed data values, as follows (split into two lines here, to fit on
19920 ACCEPT TRANSPORT=<transport> HOSTS=<list of hosts>
19921 LOOKUP=byname|bydns DATA=<text>
19923 The data items can be given in any order, and all are optional. If no transport
19924 is included, the transport specified by the generic &%transport%& option is
19925 used. The list of hosts and the lookup type are needed only if the transport is
19926 an &(smtp)& transport that does not itself supply a list of hosts.
19928 The format of the list of hosts is the same as for the &(manualroute)& router.
19929 As well as host names and IP addresses with optional port numbers, as described
19930 in section &<<SECTformatonehostitem>>&, it may contain names followed by
19931 &`/MX`& to specify sublists of hosts that are obtained by looking up MX records
19932 (see section &<<SECThostshowused>>&).
19934 If the lookup type is not specified, Exim behaves as follows when trying to
19935 find an IP address for each host: First, a DNS lookup is done. If this yields
19936 anything other than HOST_NOT_FOUND, that result is used. Otherwise, Exim
19937 goes on to try a call to &[getipnodebyname()]& or &[gethostbyname()]&, and the
19938 result of the lookup is the result of that call.
19940 .vindex "&$address_data$&"
19941 If the DATA field is set, its value is placed in the &$address_data$&
19942 variable. For example, this return line
19944 accept hosts=x1.y.example:x2.y.example data="rule1"
19946 routes the address to the default transport, passing a list of two hosts. When
19947 the transport runs, the string &"rule1"& is in &$address_data$&.
19948 .ecindex IIDquerou1
19949 .ecindex IIDquerou2
19954 . ////////////////////////////////////////////////////////////////////////////
19955 . ////////////////////////////////////////////////////////////////////////////
19957 .chapter "The redirect router" "CHAPredirect"
19958 .scindex IIDredrou1 "&(redirect)& router"
19959 .scindex IIDredrou2 "routers" "&(redirect)&"
19960 .cindex "alias file" "in a &(redirect)& router"
19961 .cindex "address redirection" "&(redirect)& router"
19962 The &(redirect)& router handles several kinds of address redirection. Its most
19963 common uses are for resolving local part aliases from a central alias file
19964 (usually called &_/etc/aliases_&) and for handling users' personal &_.forward_&
19965 files, but it has many other potential uses. The incoming address can be
19966 redirected in several different ways:
19969 It can be replaced by one or more new addresses which are themselves routed
19972 It can be routed to be delivered to a given file or directory.
19974 It can be routed to be delivered to a specified pipe command.
19976 It can cause an automatic reply to be generated.
19978 It can be forced to fail, optionally with a custom error message.
19980 It can be temporarily deferred, optionally with a custom message.
19982 It can be discarded.
19985 The generic &%transport%& option must not be set for &(redirect)& routers.
19986 However, there are some private options which define transports for delivery to
19987 files and pipes, and for generating autoreplies. See the &%file_transport%&,
19988 &%pipe_transport%& and &%reply_transport%& descriptions below.
19990 If success DSNs have been requested
19991 .cindex "DSN" "success"
19992 .cindex "Delivery Status Notification" "success"
19993 redirection triggers one and the DSN options are not passed any further.
19997 .section "Redirection data" "SECID124"
19998 The router operates by interpreting a text string which it obtains either by
19999 expanding the contents of the &%data%& option, or by reading the entire
20000 contents of a file whose name is given in the &%file%& option. These two
20001 options are mutually exclusive. The first is commonly used for handling system
20002 aliases, in a configuration like this:
20006 data = ${lookup{$local_part}lsearch{/etc/aliases}}
20008 If the lookup fails, the expanded string in this example is empty. When the
20009 expansion of &%data%& results in an empty string, the router declines. A forced
20010 expansion failure also causes the router to decline; other expansion failures
20011 cause delivery to be deferred.
20013 A configuration using &%file%& is commonly used for handling users'
20014 &_.forward_& files, like this:
20019 file = $home/.forward
20022 If the file does not exist, or causes no action to be taken (for example, it is
20023 empty or consists only of comments), the router declines. &*Warning*&: This
20024 is not the case when the file contains syntactically valid items that happen to
20025 yield empty addresses, for example, items containing only RFC 2822 address
20030 .section "Forward files and address verification" "SECID125"
20031 .cindex "address redirection" "while verifying"
20032 It is usual to set &%no_verify%& on &(redirect)& routers which handle users'
20033 &_.forward_& files, as in the example above. There are two reasons for this:
20036 When Exim is receiving an incoming SMTP message from a remote host, it is
20037 running under the Exim uid, not as root. Exim is unable to change uid to read
20038 the file as the user, and it may not be able to read it as the Exim user. So in
20039 practice the router may not be able to operate.
20041 However, even when the router can operate, the existence of a &_.forward_& file
20042 is unimportant when verifying an address. What should be checked is whether the
20043 local part is a valid user name or not. Cutting out the redirection processing
20044 saves some resources.
20052 .section "Interpreting redirection data" "SECID126"
20053 .cindex "Sieve filter" "specifying in redirection data"
20054 .cindex "filter" "specifying in redirection data"
20055 The contents of the data string, whether obtained from &%data%& or &%file%&,
20056 can be interpreted in two different ways:
20059 If the &%allow_filter%& option is set true, and the data begins with the text
20060 &"#Exim filter"& or &"#Sieve filter"&, it is interpreted as a list of
20061 &'filtering'& instructions in the form of an Exim or Sieve filter file,
20062 respectively. Details of the syntax and semantics of filter files are described
20063 in a separate document entitled &'Exim's interfaces to mail filtering'&; this
20064 document is intended for use by end users.
20066 Otherwise, the data must be a comma-separated list of redirection items, as
20067 described in the next section.
20070 When a message is redirected to a file (a &"mail folder"&), the file name given
20071 in a non-filter redirection list must always be an absolute path. A filter may
20072 generate a relative path &-- how this is handled depends on the transport's
20073 configuration. See section &<<SECTfildiropt>>& for a discussion of this issue
20074 for the &(appendfile)& transport.
20078 .section "Items in a non-filter redirection list" "SECTitenonfilred"
20079 .cindex "address redirection" "non-filter list items"
20080 When the redirection data is not an Exim or Sieve filter, for example, if it
20081 comes from a conventional alias or forward file, it consists of a list of
20082 addresses, file names, pipe commands, or certain special items (see section
20083 &<<SECTspecitredli>>& below). The special items can be individually enabled or
20084 disabled by means of options whose names begin with &%allow_%& or &%forbid_%&,
20085 depending on their default values. The items in the list are separated by
20086 commas or newlines.
20087 If a comma is required in an item, the entire item must be enclosed in double
20090 Lines starting with a # character are comments, and are ignored, and # may
20091 also appear following a comma, in which case everything between the # and the
20092 next newline character is ignored.
20094 If an item is entirely enclosed in double quotes, these are removed. Otherwise
20095 double quotes are retained because some forms of mail address require their use
20096 (but never to enclose the entire address). In the following description,
20097 &"item"& refers to what remains after any surrounding double quotes have been
20100 .vindex "&$local_part$&"
20101 &*Warning*&: If you use an Exim expansion to construct a redirection address,
20102 and the expansion contains a reference to &$local_part$&, you should make use
20103 of the &%quote_local_part%& expansion operator, in case the local part contains
20104 special characters. For example, to redirect all mail for the domain
20105 &'obsolete.example'&, retaining the existing local part, you could use this
20108 data = ${quote_local_part:$local_part}@newdomain.example
20112 .section "Redirecting to a local mailbox" "SECTredlocmai"
20113 .cindex "routing" "loops in"
20114 .cindex "loop" "while routing, avoidance of"
20115 .cindex "address redirection" "to local mailbox"
20116 A redirection item may safely be the same as the address currently under
20117 consideration. This does not cause a routing loop, because a router is
20118 automatically skipped if any ancestor of the address that is being processed
20119 is the same as the current address and was processed by the current router.
20120 Such an address is therefore passed to the following routers, so it is handled
20121 as if there were no redirection. When making this loop-avoidance test, the
20122 complete local part, including any prefix or suffix, is used.
20124 .cindex "address redirection" "local part without domain"
20125 Specifying the same local part without a domain is a common usage in personal
20126 filter files when the user wants to have messages delivered to the local
20127 mailbox and also forwarded elsewhere. For example, the user whose login is
20128 &'cleo'& might have a &_.forward_& file containing this:
20130 cleo, cleopatra@egypt.example
20132 .cindex "backslash in alias file"
20133 .cindex "alias file" "backslash in"
20134 For compatibility with other MTAs, such unqualified local parts may be
20135 preceded by &"\"&, but this is not a requirement for loop prevention. However,
20136 it does make a difference if more than one domain is being handled
20139 If an item begins with &"\"& and the rest of the item parses as a valid RFC
20140 2822 address that does not include a domain, the item is qualified using the
20141 domain of the incoming address. In the absence of a leading &"\"&, unqualified
20142 addresses are qualified using the value in &%qualify_recipient%&, but you can
20143 force the incoming domain to be used by setting &%qualify_preserve_domain%&.
20145 Care must be taken if there are alias names for local users.
20146 Consider an MTA handling a single local domain where the system alias file
20151 Now suppose that Sam (whose login id is &'spqr'&) wants to save copies of
20152 messages in the local mailbox, and also forward copies elsewhere. He creates
20155 Sam.Reman, spqr@reme.elsewhere.example
20157 With these settings, an incoming message addressed to &'Sam.Reman'& fails. The
20158 &(redirect)& router for system aliases does not process &'Sam.Reman'& the
20159 second time round, because it has previously routed it,
20160 and the following routers presumably cannot handle the alias. The forward file
20161 should really contain
20163 spqr, spqr@reme.elsewhere.example
20165 but because this is such a common error, the &%check_ancestor%& option (see
20166 below) exists to provide a way to get round it. This is normally set on a
20167 &(redirect)& router that is handling users' &_.forward_& files.
20171 .section "Special items in redirection lists" "SECTspecitredli"
20172 In addition to addresses, the following types of item may appear in redirection
20173 lists (that is, in non-filter redirection data):
20176 .cindex "pipe" "in redirection list"
20177 .cindex "address redirection" "to pipe"
20178 An item is treated as a pipe command if it begins with &"|"& and does not parse
20179 as a valid RFC 2822 address that includes a domain. A transport for running the
20180 command must be specified by the &%pipe_transport%& option.
20181 Normally, either the router or the transport specifies a user and a group under
20182 which to run the delivery. The default is to use the Exim user and group.
20184 Single or double quotes can be used for enclosing the individual arguments of
20185 the pipe command; no interpretation of escapes is done for single quotes. If
20186 the command contains a comma character, it is necessary to put the whole item
20187 in double quotes, for example:
20189 "|/some/command ready,steady,go"
20191 since items in redirection lists are terminated by commas. Do not, however,
20192 quote just the command. An item such as
20194 |"/some/command ready,steady,go"
20196 is interpreted as a pipe with a rather strange command name, and no arguments.
20198 Note that the above example assumes that the text comes from a lookup source
20199 of some sort, so that the quotes are part of the data. If composing a
20200 redirect router with a &%data%& option directly specifying this command, the
20201 quotes will be used by the configuration parser to define the extent of one
20202 string, but will not be passed down into the redirect router itself. There
20203 are two main approaches to get around this: escape quotes to be part of the
20204 data itself, or avoid using this mechanism and instead create a custom
20205 transport with the &%command%& option set and reference that transport from
20206 an &%accept%& router.
20209 .cindex "file" "in redirection list"
20210 .cindex "address redirection" "to file"
20211 An item is interpreted as a path name if it begins with &"/"& and does not
20212 parse as a valid RFC 2822 address that includes a domain. For example,
20214 /home/world/minbari
20216 is treated as a file name, but
20218 /s=molari/o=babylon/@x400gate.way
20220 is treated as an address. For a file name, a transport must be specified using
20221 the &%file_transport%& option. However, if the generated path name ends with a
20222 forward slash character, it is interpreted as a directory name rather than a
20223 file name, and &%directory_transport%& is used instead.
20225 Normally, either the router or the transport specifies a user and a group under
20226 which to run the delivery. The default is to use the Exim user and group.
20228 .cindex "&_/dev/null_&"
20229 However, if a redirection item is the path &_/dev/null_&, delivery to it is
20230 bypassed at a high level, and the log entry shows &"**bypassed**"&
20231 instead of a transport name. In this case the user and group are not used.
20234 .cindex "included address list"
20235 .cindex "address redirection" "included external list"
20236 If an item is of the form
20238 :include:<path name>
20240 a list of further items is taken from the given file and included at that
20241 point. &*Note*&: Such a file can not be a filter file; it is just an
20242 out-of-line addition to the list. The items in the included list are separated
20243 by commas or newlines and are not subject to expansion. If this is the first
20244 item in an alias list in an &(lsearch)& file, a colon must be used to terminate
20245 the alias name. This example is incorrect:
20247 list1 :include:/opt/lists/list1
20249 It must be given as
20251 list1: :include:/opt/lists/list1
20254 .cindex "address redirection" "to black hole"
20255 .cindex "delivery" "discard"
20256 .cindex "delivery" "blackhole"
20257 .cindex "black hole"
20258 .cindex "abandoning mail"
20259 Sometimes you want to throw away mail to a particular local part. Making the
20260 &%data%& option expand to an empty string does not work, because that causes
20261 the router to decline. Instead, the alias item
20265 can be used. It does what its name implies. No delivery is
20266 done, and no error message is generated. This has the same effect as specifying
20267 &_/dev/null_& as a destination, but it can be independently disabled.
20269 &*Warning*&: If &':blackhole:'& appears anywhere in a redirection list, no
20270 delivery is done for the original local part, even if other redirection items
20271 are present. If you are generating a multi-item list (for example, by reading a
20272 database) and need the ability to provide a no-op item, you must use
20276 .cindex "delivery" "forcing failure"
20277 .cindex "delivery" "forcing deferral"
20278 .cindex "failing delivery" "forcing"
20279 .cindex "deferred delivery, forcing"
20280 .cindex "customizing" "failure message"
20281 An attempt to deliver a particular address can be deferred or forced to fail by
20282 redirection items of the form
20287 respectively. When a redirection list contains such an item, it applies
20288 to the entire redirection; any other items in the list are ignored. Any
20289 text following &':fail:'& or &':defer:'& is placed in the error text
20290 associated with the failure. For example, an alias file might contain:
20292 X.Employee: :fail: Gone away, no forwarding address
20294 In the case of an address that is being verified from an ACL or as the subject
20296 .cindex "VRFY" "error text, display of"
20297 VRFY command, the text is included in the SMTP error response by
20299 .cindex "EXPN" "error text, display of"
20300 The text is not included in the response to an EXPN command. In non-SMTP cases
20301 the text is included in the error message that Exim generates.
20303 .cindex "SMTP" "error codes"
20304 By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
20305 &':fail:'&. However, if the message starts with three digits followed by a
20306 space, optionally followed by an extended code of the form &'n.n.n'&, also
20307 followed by a space, and the very first digit is the same as the default error
20308 code, the code from the message is used instead. If the very first digit is
20309 incorrect, a panic error is logged, and the default code is used. You can
20310 suppress the use of the supplied code in a redirect router by setting the
20311 &%forbid_smtp_code%& option true. In this case, any SMTP code is quietly
20314 .vindex "&$acl_verify_message$&"
20315 In an ACL, an explicitly provided message overrides the default, but the
20316 default message is available in the variable &$acl_verify_message$& and can
20317 therefore be included in a custom message if this is desired.
20319 Normally the error text is the rest of the redirection list &-- a comma does
20320 not terminate it &-- but a newline does act as a terminator. Newlines are not
20321 normally present in alias expansions. In &(lsearch)& lookups they are removed
20322 as part of the continuation process, but they may exist in other kinds of
20323 lookup and in &':include:'& files.
20325 During routing for message delivery (as opposed to verification), a redirection
20326 containing &':fail:'& causes an immediate failure of the incoming address,
20327 whereas &':defer:'& causes the message to remain on the queue so that a
20328 subsequent delivery attempt can happen at a later time. If an address is
20329 deferred for too long, it will ultimately fail, because the normal retry
20333 .cindex "alias file" "exception to default"
20334 Sometimes it is useful to use a single-key search type with a default (see
20335 chapter &<<CHAPfdlookup>>&) to look up aliases. However, there may be a need
20336 for exceptions to the default. These can be handled by aliasing them to
20337 &':unknown:'&. This differs from &':fail:'& in that it causes the &(redirect)&
20338 router to decline, whereas &':fail:'& forces routing to fail. A lookup which
20339 results in an empty redirection list has the same effect.
20343 .section "Duplicate addresses" "SECTdupaddr"
20344 .cindex "duplicate addresses"
20345 .cindex "address duplicate, discarding"
20346 .cindex "pipe" "duplicated"
20347 Exim removes duplicate addresses from the list to which it is delivering, so as
20348 to deliver just one copy to each address. This does not apply to deliveries
20349 routed to pipes by different immediate parent addresses, but an indirect
20350 aliasing scheme of the type
20352 pipe: |/some/command $local_part
20356 does not work with a message that is addressed to both local parts, because
20357 when the second is aliased to the intermediate local part &"pipe"& it gets
20358 discarded as being the same as a previously handled address. However, a scheme
20361 localpart1: |/some/command $local_part
20362 localpart2: |/some/command $local_part
20364 does result in two different pipe deliveries, because the immediate parents of
20365 the pipes are distinct.
20369 .section "Repeated redirection expansion" "SECID128"
20370 .cindex "repeated redirection expansion"
20371 .cindex "address redirection" "repeated for each delivery attempt"
20372 When a message cannot be delivered to all of its recipients immediately,
20373 leading to two or more delivery attempts, redirection expansion is carried out
20374 afresh each time for those addresses whose children were not all previously
20375 delivered. If redirection is being used as a mailing list, this can lead to new
20376 members of the list receiving copies of old messages. The &%one_time%& option
20377 can be used to avoid this.
20380 .section "Errors in redirection lists" "SECID129"
20381 .cindex "address redirection" "errors"
20382 If &%skip_syntax_errors%& is set, a malformed address that causes a parsing
20383 error is skipped, and an entry is written to the main log. This may be useful
20384 for mailing lists that are automatically managed. Otherwise, if an error is
20385 detected while generating the list of new addresses, the original address is
20386 deferred. See also &%syntax_errors_to%&.
20390 .section "Private options for the redirect router" "SECID130"
20392 .cindex "options" "&(redirect)& router"
20393 The private options for the &(redirect)& router are as follows:
20396 .option allow_defer redirect boolean false
20397 Setting this option allows the use of &':defer:'& in non-filter redirection
20398 data, or the &%defer%& command in an Exim filter file.
20401 .option allow_fail redirect boolean false
20402 .cindex "failing delivery" "from filter"
20403 If this option is true, the &':fail:'& item can be used in a redirection list,
20404 and the &%fail%& command may be used in an Exim filter file.
20407 .option allow_filter redirect boolean false
20408 .cindex "filter" "enabling use of"
20409 .cindex "Sieve filter" "enabling use of"
20410 Setting this option allows Exim to interpret redirection data that starts with
20411 &"#Exim filter"& or &"#Sieve filter"& as a set of filtering instructions. There
20412 are some features of Exim filter files that some administrators may wish to
20413 lock out; see the &%forbid_filter_%&&'xxx'& options below.
20415 It is also possible to lock out Exim filters or Sieve filters while allowing
20416 the other type; see &%forbid_exim_filter%& and &%forbid_sieve_filter%&.
20419 The filter is run using the uid and gid set by the generic &%user%& and
20420 &%group%& options. These take their defaults from the password data if
20421 &%check_local_user%& is set, so in the normal case of users' personal filter
20422 files, the filter is run as the relevant user. When &%allow_filter%& is set
20423 true, Exim insists that either &%check_local_user%& or &%user%& is set.
20427 .option allow_freeze redirect boolean false
20428 .cindex "freezing messages" "allowing in filter"
20429 Setting this option allows the use of the &%freeze%& command in an Exim filter.
20430 This command is more normally encountered in system filters, and is disabled by
20431 default for redirection filters because it isn't something you usually want to
20432 let ordinary users do.
20436 .option check_ancestor redirect boolean false
20437 This option is concerned with handling generated addresses that are the same
20438 as some address in the list of redirection ancestors of the current address.
20439 Although it is turned off by default in the code, it is set in the default
20440 configuration file for handling users' &_.forward_& files. It is recommended
20441 for this use of the &(redirect)& router.
20443 When &%check_ancestor%& is set, if a generated address (including the domain)
20444 is the same as any ancestor of the current address, it is replaced by a copy of
20445 the current address. This helps in the case where local part A is aliased to B,
20446 and B has a &_.forward_& file pointing back to A. For example, within a single
20447 domain, the local part &"Joe.Bloggs"& is aliased to &"jb"& and
20448 &_&~jb/.forward_& contains:
20450 \Joe.Bloggs, <other item(s)>
20452 Without the &%check_ancestor%& setting, either local part (&"jb"& or
20453 &"joe.bloggs"&) gets processed once by each router and so ends up as it was
20454 originally. If &"jb"& is the real mailbox name, mail to &"jb"& gets delivered
20455 (having been turned into &"joe.bloggs"& by the &_.forward_& file and back to
20456 &"jb"& by the alias), but mail to &"joe.bloggs"& fails. Setting
20457 &%check_ancestor%& on the &(redirect)& router that handles the &_.forward_&
20458 file prevents it from turning &"jb"& back into &"joe.bloggs"& when that was the
20459 original address. See also the &%repeat_use%& option below.
20462 .option check_group redirect boolean "see below"
20463 When the &%file%& option is used, the group owner of the file is checked only
20464 when this option is set. The permitted groups are those listed in the
20465 &%owngroups%& option, together with the user's default group if
20466 &%check_local_user%& is set. If the file has the wrong group, routing is
20467 deferred. The default setting for this option is true if &%check_local_user%&
20468 is set and the &%modemask%& option permits the group write bit, or if the
20469 &%owngroups%& option is set. Otherwise it is false, and no group check occurs.
20473 .option check_owner redirect boolean "see below"
20474 When the &%file%& option is used, the owner of the file is checked only when
20475 this option is set. If &%check_local_user%& is set, the local user is
20476 permitted; otherwise the owner must be one of those listed in the &%owners%&
20477 option. The default value for this option is true if &%check_local_user%& or
20478 &%owners%& is set. Otherwise the default is false, and no owner check occurs.
20481 .option data redirect string&!! unset
20482 This option is mutually exclusive with &%file%&. One or other of them must be
20483 set, but not both. The contents of &%data%& are expanded, and then used as the
20484 list of forwarding items, or as a set of filtering instructions. If the
20485 expansion is forced to fail, or the result is an empty string or a string that
20486 has no effect (consists entirely of comments), the router declines.
20488 When filtering instructions are used, the string must begin with &"#Exim
20489 filter"&, and all comments in the string, including this initial one, must be
20490 terminated with newline characters. For example:
20492 data = #Exim filter\n\
20493 if $h_to: contains Exim then save $home/mail/exim endif
20495 If you are reading the data from a database where newlines cannot be included,
20496 you can use the &${sg}$& expansion item to turn the escape string of your
20497 choice into a newline.
20500 .option directory_transport redirect string&!! unset
20501 A &(redirect)& router sets up a direct delivery to a directory when a path name
20502 ending with a slash is specified as a new &"address"&. The transport used is
20503 specified by this option, which, after expansion, must be the name of a
20504 configured transport. This should normally be an &(appendfile)& transport.
20507 .option file redirect string&!! unset
20508 This option specifies the name of a file that contains the redirection data. It
20509 is mutually exclusive with the &%data%& option. The string is expanded before
20510 use; if the expansion is forced to fail, the router declines. Other expansion
20511 failures cause delivery to be deferred. The result of a successful expansion
20512 must be an absolute path. The entire file is read and used as the redirection
20513 data. If the data is an empty string or a string that has no effect (consists
20514 entirely of comments), the router declines.
20516 .cindex "NFS" "checking for file existence"
20517 If the attempt to open the file fails with a &"does not exist"& error, Exim
20518 runs a check on the containing directory,
20519 unless &%ignore_enotdir%& is true (see below).
20520 If the directory does not appear to exist, delivery is deferred. This can
20521 happen when users' &_.forward_& files are in NFS-mounted directories, and there
20522 is a mount problem. If the containing directory does exist, but the file does
20523 not, the router declines.
20526 .option file_transport redirect string&!! unset
20527 .vindex "&$address_file$&"
20528 A &(redirect)& router sets up a direct delivery to a file when a path name not
20529 ending in a slash is specified as a new &"address"&. The transport used is
20530 specified by this option, which, after expansion, must be the name of a
20531 configured transport. This should normally be an &(appendfile)& transport. When
20532 it is running, the file name is in &$address_file$&.
20535 .option filter_prepend_home redirect boolean true
20536 When this option is true, if a &(save)& command in an Exim filter specifies a
20537 relative path, and &$home$& is defined, it is automatically prepended to the
20538 relative path. If this option is set false, this action does not happen. The
20539 relative path is then passed to the transport unmodified.
20542 .option forbid_blackhole redirect boolean false
20543 .cindex "restricting access to features"
20544 .cindex "filter" "locking out certain features"
20545 If this option is true, the &':blackhole:'& item may not appear in a
20549 .option forbid_exim_filter redirect boolean false
20550 .cindex "restricting access to features"
20551 .cindex "filter" "locking out certain features"
20552 If this option is set true, only Sieve filters are permitted when
20553 &%allow_filter%& is true.
20558 .option forbid_file redirect boolean false
20559 .cindex "restricting access to features"
20560 .cindex "delivery" "to file; forbidding"
20561 .cindex "filter" "locking out certain features"
20562 .cindex "Sieve filter" "forbidding delivery to a file"
20563 .cindex "Sieve filter" "&""keep""& facility; disabling"
20564 If this option is true, this router may not generate a new address that
20565 specifies delivery to a local file or directory, either from a filter or from a
20566 conventional forward file. This option is forced to be true if &%one_time%& is
20567 set. It applies to Sieve filters as well as to Exim filters, but if true, it
20568 locks out the Sieve's &"keep"& facility.
20571 .option forbid_filter_dlfunc redirect boolean false
20572 .cindex "restricting access to features"
20573 .cindex "filter" "locking out certain features"
20574 If this option is true, string expansions in Exim filters are not allowed to
20575 make use of the &%dlfunc%& expansion facility to run dynamically loaded
20578 .option forbid_filter_existstest redirect boolean false
20579 .cindex "restricting access to features"
20580 .cindex "filter" "locking out certain features"
20581 .cindex "expansion" "statting a file"
20582 If this option is true, string expansions in Exim filters are not allowed to
20583 make use of the &%exists%& condition or the &%stat%& expansion item.
20585 .option forbid_filter_logwrite redirect boolean false
20586 .cindex "restricting access to features"
20587 .cindex "filter" "locking out certain features"
20588 If this option is true, use of the logging facility in Exim filters is not
20589 permitted. Logging is in any case available only if the filter is being run
20590 under some unprivileged uid (which is normally the case for ordinary users'
20591 &_.forward_& files).
20594 .option forbid_filter_lookup redirect boolean false
20595 .cindex "restricting access to features"
20596 .cindex "filter" "locking out certain features"
20597 If this option is true, string expansions in Exim filter files are not allowed
20598 to make use of &%lookup%& items.
20601 .option forbid_filter_perl redirect boolean false
20602 .cindex "restricting access to features"
20603 .cindex "filter" "locking out certain features"
20604 This option has an effect only if Exim is built with embedded Perl support. If
20605 it is true, string expansions in Exim filter files are not allowed to make use
20606 of the embedded Perl support.
20609 .option forbid_filter_readfile redirect boolean false
20610 .cindex "restricting access to features"
20611 .cindex "filter" "locking out certain features"
20612 If this option is true, string expansions in Exim filter files are not allowed
20613 to make use of &%readfile%& items.
20616 .option forbid_filter_readsocket redirect boolean false
20617 .cindex "restricting access to features"
20618 .cindex "filter" "locking out certain features"
20619 If this option is true, string expansions in Exim filter files are not allowed
20620 to make use of &%readsocket%& items.
20623 .option forbid_filter_reply redirect boolean false
20624 .cindex "restricting access to features"
20625 .cindex "filter" "locking out certain features"
20626 If this option is true, this router may not generate an automatic reply
20627 message. Automatic replies can be generated only from Exim or Sieve filter
20628 files, not from traditional forward files. This option is forced to be true if
20629 &%one_time%& is set.
20632 .option forbid_filter_run redirect boolean false
20633 .cindex "restricting access to features"
20634 .cindex "filter" "locking out certain features"
20635 If this option is true, string expansions in Exim filter files are not allowed
20636 to make use of &%run%& items.
20639 .option forbid_include redirect boolean false
20640 .cindex "restricting access to features"
20641 .cindex "filter" "locking out certain features"
20642 If this option is true, items of the form
20644 :include:<path name>
20646 are not permitted in non-filter redirection lists.
20649 .option forbid_pipe redirect boolean false
20650 .cindex "restricting access to features"
20651 .cindex "filter" "locking out certain features"
20652 .cindex "delivery" "to pipe; forbidding"
20653 If this option is true, this router may not generate a new address which
20654 specifies delivery to a pipe, either from an Exim filter or from a conventional
20655 forward file. This option is forced to be true if &%one_time%& is set.
20658 .option forbid_sieve_filter redirect boolean false
20659 .cindex "restricting access to features"
20660 .cindex "filter" "locking out certain features"
20661 If this option is set true, only Exim filters are permitted when
20662 &%allow_filter%& is true.
20665 .cindex "SMTP" "error codes"
20666 .option forbid_smtp_code redirect boolean false
20667 If this option is set true, any SMTP error codes that are present at the start
20668 of messages specified for &`:defer:`& or &`:fail:`& are quietly ignored, and
20669 the default codes (451 and 550, respectively) are always used.
20674 .option hide_child_in_errmsg redirect boolean false
20675 .cindex "bounce message" "redirection details; suppressing"
20676 If this option is true, it prevents Exim from quoting a child address if it
20677 generates a bounce or delay message for it. Instead it says &"an address
20678 generated from <&'the top level address'&>"&. Of course, this applies only to
20679 bounces generated locally. If a message is forwarded to another host, &'its'&
20680 bounce may well quote the generated address.
20683 .option ignore_eacces redirect boolean false
20685 If this option is set and an attempt to open a redirection file yields the
20686 EACCES error (permission denied), the &(redirect)& router behaves as if the
20687 file did not exist.
20690 .option ignore_enotdir redirect boolean false
20692 If this option is set and an attempt to open a redirection file yields the
20693 ENOTDIR error (something on the path is not a directory), the &(redirect)&
20694 router behaves as if the file did not exist.
20696 Setting &%ignore_enotdir%& has another effect as well: When a &(redirect)&
20697 router that has the &%file%& option set discovers that the file does not exist
20698 (the ENOENT error), it tries to &[stat()]& the parent directory, as a check
20699 against unmounted NFS directories. If the parent can not be statted, delivery
20700 is deferred. However, it seems wrong to do this check when &%ignore_enotdir%&
20701 is set, because that option tells Exim to ignore &"something on the path is not
20702 a directory"& (the ENOTDIR error). This is a confusing area, because it seems
20703 that some operating systems give ENOENT where others give ENOTDIR.
20707 .option include_directory redirect string unset
20708 If this option is set, the path names of any &':include:'& items in a
20709 redirection list must start with this directory.
20712 .option modemask redirect "octal integer" 022
20713 This specifies mode bits which must not be set for a file specified by the
20714 &%file%& option. If any of the forbidden bits are set, delivery is deferred.
20717 .option one_time redirect boolean false
20718 .cindex "one-time aliasing/forwarding expansion"
20719 .cindex "alias file" "one-time expansion"
20720 .cindex "forward file" "one-time expansion"
20721 .cindex "mailing lists" "one-time expansion"
20722 .cindex "address redirection" "one-time expansion"
20723 Sometimes the fact that Exim re-evaluates aliases and reprocesses redirection
20724 files each time it tries to deliver a message causes a problem when one or more
20725 of the generated addresses fails be delivered at the first attempt. The problem
20726 is not one of duplicate delivery &-- Exim is clever enough to handle that &--
20727 but of what happens when the redirection list changes during the time that the
20728 message is on Exim's queue. This is particularly true in the case of mailing
20729 lists, where new subscribers might receive copies of messages that were posted
20730 before they subscribed.
20732 If &%one_time%& is set and any addresses generated by the router fail to
20733 deliver at the first attempt, the failing addresses are added to the message as
20734 &"top level"& addresses, and the parent address that generated them is marked
20735 &"delivered"&. Thus, redirection does not happen again at the next delivery
20738 &*Warning 1*&: Any header line addition or removal that is specified by this
20739 router would be lost if delivery did not succeed at the first attempt. For this
20740 reason, the &%headers_add%& and &%headers_remove%& generic options are not
20741 permitted when &%one_time%& is set.
20743 &*Warning 2*&: To ensure that the router generates only addresses (as opposed
20744 to pipe or file deliveries or auto-replies) &%forbid_file%&, &%forbid_pipe%&,
20745 and &%forbid_filter_reply%& are forced to be true when &%one_time%& is set.
20747 &*Warning 3*&: The &%unseen%& generic router option may not be set with
20750 The original top-level address is remembered with each of the generated
20751 addresses, and is output in any log messages. However, any intermediate parent
20752 addresses are not recorded. This makes a difference to the log only if
20753 &%all_parents%& log selector is set. It is expected that &%one_time%& will
20754 typically be used for mailing lists, where there is normally just one level of
20758 .option owners redirect "string list" unset
20759 .cindex "ownership" "alias file"
20760 .cindex "ownership" "forward file"
20761 .cindex "alias file" "ownership"
20762 .cindex "forward file" "ownership"
20763 This specifies a list of permitted owners for the file specified by &%file%&.
20764 This list is in addition to the local user when &%check_local_user%& is set.
20765 See &%check_owner%& above.
20768 .option owngroups redirect "string list" unset
20769 This specifies a list of permitted groups for the file specified by &%file%&.
20770 The list is in addition to the local user's primary group when
20771 &%check_local_user%& is set. See &%check_group%& above.
20774 .option pipe_transport redirect string&!! unset
20775 .vindex "&$address_pipe$&"
20776 A &(redirect)& router sets up a direct delivery to a pipe when a string
20777 starting with a vertical bar character is specified as a new &"address"&. The
20778 transport used is specified by this option, which, after expansion, must be the
20779 name of a configured transport. This should normally be a &(pipe)& transport.
20780 When the transport is run, the pipe command is in &$address_pipe$&.
20783 .option qualify_domain redirect string&!! unset
20784 .vindex "&$qualify_recipient$&"
20785 If this option is set, and an unqualified address (one without a domain) is
20786 generated, and that address would normally be qualified by the global setting
20787 in &%qualify_recipient%&, it is instead qualified with the domain specified by
20788 expanding this string. If the expansion fails, the router declines. If you want
20789 to revert to the default, you can have the expansion generate
20790 &$qualify_recipient$&.
20792 This option applies to all unqualified addresses generated by Exim filters,
20793 but for traditional &_.forward_& files, it applies only to addresses that are
20794 not preceded by a backslash. Sieve filters cannot generate unqualified
20797 .option qualify_preserve_domain redirect boolean false
20798 .cindex "domain" "in redirection; preserving"
20799 .cindex "preserving domain in redirection"
20800 .cindex "address redirection" "domain; preserving"
20801 If this option is set, the router's local &%qualify_domain%& option must not be
20802 set (a configuration error occurs if it is). If an unqualified address (one
20803 without a domain) is generated, it is qualified with the domain of the parent
20804 address (the immediately preceding ancestor) instead of the global
20805 &%qualify_recipient%& value. In the case of a traditional &_.forward_& file,
20806 this applies whether or not the address is preceded by a backslash.
20809 .option repeat_use redirect boolean true
20810 If this option is set false, the router is skipped for a child address that has
20811 any ancestor that was routed by this router. This test happens before any of
20812 the other preconditions are tested. Exim's default anti-looping rules skip
20813 only when the ancestor is the same as the current address. See also
20814 &%check_ancestor%& above and the generic &%redirect_router%& option.
20817 .option reply_transport redirect string&!! unset
20818 A &(redirect)& router sets up an automatic reply when a &%mail%& or
20819 &%vacation%& command is used in a filter file. The transport used is specified
20820 by this option, which, after expansion, must be the name of a configured
20821 transport. This should normally be an &(autoreply)& transport. Other transports
20822 are unlikely to do anything sensible or useful.
20825 .option rewrite redirect boolean true
20826 .cindex "address redirection" "disabling rewriting"
20827 If this option is set false, addresses generated by the router are not
20828 subject to address rewriting. Otherwise, they are treated like new addresses
20829 and are rewritten according to the global rewriting rules.
20832 .option sieve_subaddress redirect string&!! unset
20833 The value of this option is passed to a Sieve filter to specify the
20834 :subaddress part of an address.
20836 .option sieve_useraddress redirect string&!! unset
20837 The value of this option is passed to a Sieve filter to specify the :user part
20838 of an address. However, if it is unset, the entire original local part
20839 (including any prefix or suffix) is used for :user.
20842 .option sieve_vacation_directory redirect string&!! unset
20843 .cindex "Sieve filter" "vacation directory"
20844 To enable the &"vacation"& extension for Sieve filters, you must set
20845 &%sieve_vacation_directory%& to the directory where vacation databases are held
20846 (do not put anything else in that directory), and ensure that the
20847 &%reply_transport%& option refers to an &(autoreply)& transport. Each user
20848 needs their own directory; Exim will create it if necessary.
20852 .option skip_syntax_errors redirect boolean false
20853 .cindex "forward file" "broken"
20854 .cindex "address redirection" "broken files"
20855 .cindex "alias file" "broken"
20856 .cindex "broken alias or forward files"
20857 .cindex "ignoring faulty addresses"
20858 .cindex "skipping faulty addresses"
20859 .cindex "error" "skipping bad syntax"
20860 If &%skip_syntax_errors%& is set, syntactically malformed addresses in
20861 non-filter redirection data are skipped, and each failing address is logged. If
20862 &%syntax_errors_to%& is set, a message is sent to the address it defines,
20863 giving details of the failures. If &%syntax_errors_text%& is set, its contents
20864 are expanded and placed at the head of the error message generated by
20865 &%syntax_errors_to%&. Usually it is appropriate to set &%syntax_errors_to%& to
20866 be the same address as the generic &%errors_to%& option. The
20867 &%skip_syntax_errors%& option is often used when handling mailing lists.
20869 If all the addresses in a redirection list are skipped because of syntax
20870 errors, the router declines to handle the original address, and it is passed to
20871 the following routers.
20873 If &%skip_syntax_errors%& is set when an Exim filter is interpreted, any syntax
20874 error in the filter causes filtering to be abandoned without any action being
20875 taken. The incident is logged, and the router declines to handle the address,
20876 so it is passed to the following routers.
20878 .cindex "Sieve filter" "syntax errors in"
20879 Syntax errors in a Sieve filter file cause the &"keep"& action to occur. This
20880 action is specified by RFC 3028. The values of &%skip_syntax_errors%&,
20881 &%syntax_errors_to%&, and &%syntax_errors_text%& are not used.
20883 &%skip_syntax_errors%& can be used to specify that errors in users' forward
20884 lists or filter files should not prevent delivery. The &%syntax_errors_to%&
20885 option, used with an address that does not get redirected, can be used to
20886 notify users of these errors, by means of a router like this:
20892 file = $home/.forward
20893 file_transport = address_file
20894 pipe_transport = address_pipe
20895 reply_transport = address_reply
20898 syntax_errors_to = real-$local_part@$domain
20899 syntax_errors_text = \
20900 This is an automatically generated message. An error has\n\
20901 been found in your .forward file. Details of the error are\n\
20902 reported below. While this error persists, you will receive\n\
20903 a copy of this message for every message that is addressed\n\
20904 to you. If your .forward file is a filter file, or if it is\n\
20905 a non-filter file containing no valid forwarding addresses,\n\
20906 a copy of each incoming message will be put in your normal\n\
20907 mailbox. If a non-filter file contains at least one valid\n\
20908 forwarding address, forwarding to the valid addresses will\n\
20909 happen, and those will be the only deliveries that occur.
20911 You also need a router to ensure that local addresses that are prefixed by
20912 &`real-`& are recognized, but not forwarded or filtered. For example, you could
20913 put this immediately before the &(userforward)& router:
20918 local_part_prefix = real-
20919 transport = local_delivery
20921 For security, it would probably be a good idea to restrict the use of this
20922 router to locally-generated messages, using a condition such as this:
20924 condition = ${if match {$sender_host_address}\
20925 {\N^(|127\.0\.0\.1)$\N}}
20929 .option syntax_errors_text redirect string&!! unset
20930 See &%skip_syntax_errors%& above.
20933 .option syntax_errors_to redirect string unset
20934 See &%skip_syntax_errors%& above.
20935 .ecindex IIDredrou1
20936 .ecindex IIDredrou2
20943 . ////////////////////////////////////////////////////////////////////////////
20944 . ////////////////////////////////////////////////////////////////////////////
20946 .chapter "Environment for running local transports" "CHAPenvironment" &&&
20947 "Environment for local transports"
20948 .scindex IIDenvlotra1 "local transports" "environment for"
20949 .scindex IIDenvlotra2 "environment" "local transports"
20950 .scindex IIDenvlotra3 "transport" "local; environment for"
20951 Local transports handle deliveries to files and pipes. (The &(autoreply)&
20952 transport can be thought of as similar to a pipe.) Exim always runs transports
20953 in subprocesses, under specified uids and gids. Typical deliveries to local
20954 mailboxes run under the uid and gid of the local user.
20956 Exim also sets a specific current directory while running the transport; for
20957 some transports a home directory setting is also relevant. The &(pipe)&
20958 transport is the only one that sets up environment variables; see section
20959 &<<SECTpipeenv>>& for details.
20961 The values used for the uid, gid, and the directories may come from several
20962 different places. In many cases, the router that handles the address associates
20963 settings with that address as a result of its &%check_local_user%&, &%group%&,
20964 or &%user%& options. However, values may also be given in the transport's own
20965 configuration, and these override anything that comes from the router.
20969 .section "Concurrent deliveries" "SECID131"
20970 .cindex "concurrent deliveries"
20971 .cindex "simultaneous deliveries"
20972 If two different messages for the same local recipient arrive more or less
20973 simultaneously, the two delivery processes are likely to run concurrently. When
20974 the &(appendfile)& transport is used to write to a file, Exim applies locking
20975 rules to stop concurrent processes from writing to the same file at the same
20978 However, when you use a &(pipe)& transport, it is up to you to arrange any
20979 locking that is needed. Here is a silly example:
20983 command = /bin/sh -c 'cat >>/some/file'
20985 This is supposed to write the message at the end of the file. However, if two
20986 messages arrive at the same time, the file will be scrambled. You can use the
20987 &%exim_lock%& utility program (see section &<<SECTmailboxmaint>>&) to lock a
20988 file using the same algorithm that Exim itself uses.
20993 .section "Uids and gids" "SECTenvuidgid"
20994 .cindex "local transports" "uid and gid"
20995 .cindex "transport" "local; uid and gid"
20996 All transports have the options &%group%& and &%user%&. If &%group%& is set, it
20997 overrides any group that the router set in the address, even if &%user%& is not
20998 set for the transport. This makes it possible, for example, to run local mail
20999 delivery under the uid of the recipient (set by the router), but in a special
21000 group (set by the transport). For example:
21003 # User/group are set by check_local_user in this router
21007 transport = group_delivery
21010 # This transport overrides the group
21012 driver = appendfile
21013 file = /var/spool/mail/$local_part
21016 If &%user%& is set for a transport, its value overrides what is set in the
21017 address by the router. If &%user%& is non-numeric and &%group%& is not set, the
21018 gid associated with the user is used. If &%user%& is numeric, &%group%& must be
21021 .oindex "&%initgroups%&"
21022 When the uid is taken from the transport's configuration, the &[initgroups()]&
21023 function is called for the groups associated with that uid if the
21024 &%initgroups%& option is set for the transport. When the uid is not specified
21025 by the transport, but is associated with the address by a router, the option
21026 for calling &[initgroups()]& is taken from the router configuration.
21028 .cindex "&(pipe)& transport" "uid for"
21029 The &(pipe)& transport contains the special option &%pipe_as_creator%&. If this
21030 is set and &%user%& is not set, the uid of the process that called Exim to
21031 receive the message is used, and if &%group%& is not set, the corresponding
21032 original gid is also used.
21034 This is the detailed preference order for obtaining a gid; the first of the
21035 following that is set is used:
21038 A &%group%& setting of the transport;
21040 A &%group%& setting of the router;
21042 A gid associated with a user setting of the router, either as a result of
21043 &%check_local_user%& or an explicit non-numeric &%user%& setting;
21045 The group associated with a non-numeric &%user%& setting of the transport;
21047 In a &(pipe)& transport, the creator's gid if &%deliver_as_creator%& is set and
21048 the uid is the creator's uid;
21050 The Exim gid if the Exim uid is being used as a default.
21053 If, for example, the user is specified numerically on the router and there are
21054 no group settings, no gid is available. In this situation, an error occurs.
21055 This is different for the uid, for which there always is an ultimate default.
21056 The first of the following that is set is used:
21059 A &%user%& setting of the transport;
21061 In a &(pipe)& transport, the creator's uid if &%deliver_as_creator%& is set;
21063 A &%user%& setting of the router;
21065 A &%check_local_user%& setting of the router;
21070 Of course, an error will still occur if the uid that is chosen is on the
21071 &%never_users%& list.
21077 .section "Current and home directories" "SECID132"
21078 .cindex "current directory for local transport"
21079 .cindex "home directory" "for local transport"
21080 .cindex "transport" "local; home directory for"
21081 .cindex "transport" "local; current directory for"
21082 Routers may set current and home directories for local transports by means of
21083 the &%transport_current_directory%& and &%transport_home_directory%& options.
21084 However, if the transport's &%current_directory%& or &%home_directory%& options
21085 are set, they override the router's values. In detail, the home directory
21086 for a local transport is taken from the first of these values that is set:
21089 The &%home_directory%& option on the transport;
21091 The &%transport_home_directory%& option on the router;
21093 The password data if &%check_local_user%& is set on the router;
21095 The &%router_home_directory%& option on the router.
21098 The current directory is taken from the first of these values that is set:
21101 The &%current_directory%& option on the transport;
21103 The &%transport_current_directory%& option on the router.
21107 If neither the router nor the transport sets a current directory, Exim uses the
21108 value of the home directory, if it is set. Otherwise it sets the current
21109 directory to &_/_& before running a local transport.
21113 .section "Expansion variables derived from the address" "SECID133"
21114 .vindex "&$domain$&"
21115 .vindex "&$local_part$&"
21116 .vindex "&$original_domain$&"
21117 Normally a local delivery is handling a single address, and in that case the
21118 variables such as &$domain$& and &$local_part$& are set during local
21119 deliveries. However, in some circumstances more than one address may be handled
21120 at once (for example, while writing batch SMTP for onward transmission by some
21121 other means). In this case, the variables associated with the local part are
21122 never set, &$domain$& is set only if all the addresses have the same domain,
21123 and &$original_domain$& is never set.
21124 .ecindex IIDenvlotra1
21125 .ecindex IIDenvlotra2
21126 .ecindex IIDenvlotra3
21134 . ////////////////////////////////////////////////////////////////////////////
21135 . ////////////////////////////////////////////////////////////////////////////
21137 .chapter "Generic options for transports" "CHAPtransportgeneric"
21138 .scindex IIDgenoptra1 "generic options" "transport"
21139 .scindex IIDgenoptra2 "options" "generic; for transports"
21140 .scindex IIDgenoptra3 "transport" "generic options for"
21141 The following generic options apply to all transports:
21144 .option body_only transports boolean false
21145 .cindex "transport" "body only"
21146 .cindex "message" "transporting body only"
21147 .cindex "body of message" "transporting"
21148 If this option is set, the message's headers are not transported. It is
21149 mutually exclusive with &%headers_only%&. If it is used with the &(appendfile)&
21150 or &(pipe)& transports, the settings of &%message_prefix%& and
21151 &%message_suffix%& should be checked, because this option does not
21152 automatically suppress them.
21155 .option current_directory transports string&!! unset
21156 .cindex "transport" "current directory for"
21157 This specifies the current directory that is to be set while running the
21158 transport, overriding any value that may have been set by the router.
21159 If the expansion fails for any reason, including forced failure, an error is
21160 logged, and delivery is deferred.
21163 .option disable_logging transports boolean false
21164 If this option is set true, nothing is logged for any
21165 deliveries by the transport or for any
21166 transport errors. You should not set this option unless you really, really know
21167 what you are doing.
21170 .option debug_print transports string&!! unset
21171 .cindex "testing" "variables in drivers"
21172 If this option is set and debugging is enabled (see the &%-d%& command line
21173 option), the string is expanded and included in the debugging output when the
21175 If expansion of the string fails, the error message is written to the debugging
21176 output, and Exim carries on processing.
21177 This facility is provided to help with checking out the values of variables and
21178 so on when debugging driver configurations. For example, if a &%headers_add%&
21179 option is not working properly, &%debug_print%& could be used to output the
21180 variables it references. A newline is added to the text if it does not end with
21182 The variables &$transport_name$& and &$router_name$& contain the name of the
21183 transport and the router that called it.
21185 .option delivery_date_add transports boolean false
21186 .cindex "&'Delivery-date:'& header line"
21187 If this option is true, a &'Delivery-date:'& header is added to the message.
21188 This gives the actual time the delivery was made. As this is not a standard
21189 header, Exim has a configuration option (&%delivery_date_remove%&) which
21190 requests its removal from incoming messages, so that delivered messages can
21191 safely be resent to other recipients.
21194 .option driver transports string unset
21195 This specifies which of the available transport drivers is to be used.
21196 There is no default, and this option must be set for every transport.
21199 .option envelope_to_add transports boolean false
21200 .cindex "&'Envelope-to:'& header line"
21201 If this option is true, an &'Envelope-to:'& header is added to the message.
21202 This gives the original address(es) in the incoming envelope that caused this
21203 delivery to happen. More than one address may be present if the transport is
21204 configured to handle several addresses at once, or if more than one original
21205 address was redirected to the same final address. As this is not a standard
21206 header, Exim has a configuration option (&%envelope_to_remove%&) which requests
21207 its removal from incoming messages, so that delivered messages can safely be
21208 resent to other recipients.
21211 .option event_action transports string&!! unset
21213 This option declares a string to be expanded for Exim's events mechanism.
21214 For details see chapter &<<CHAPevents>>&.
21217 .option group transports string&!! "Exim group"
21218 .cindex "transport" "group; specifying"
21219 This option specifies a gid for running the transport process, overriding any
21220 value that the router supplies, and also overriding any value associated with
21221 &%user%& (see below).
21224 .option headers_add transports list&!! unset
21225 .cindex "header lines" "adding in transport"
21226 .cindex "transport" "header lines; adding"
21227 This option specifies a list of text headers,
21228 newline-separated (by default, changeable in the usual way),
21229 which are (separately) expanded and added to the header
21230 portion of a message as it is transported, as described in section
21231 &<<SECTheadersaddrem>>&. Additional header lines can also be specified by
21232 routers. If the result of the expansion is an empty string, or if the expansion
21233 is forced to fail, no action is taken. Other expansion failures are treated as
21234 errors and cause the delivery to be deferred.
21236 Unlike most options, &%headers_add%& can be specified multiple times
21237 for a transport; all listed headers are added.
21240 .option headers_only transports boolean false
21241 .cindex "transport" "header lines only"
21242 .cindex "message" "transporting headers only"
21243 .cindex "header lines" "transporting"
21244 If this option is set, the message's body is not transported. It is mutually
21245 exclusive with &%body_only%&. If it is used with the &(appendfile)& or &(pipe)&
21246 transports, the settings of &%message_prefix%& and &%message_suffix%& should be
21247 checked, since this option does not automatically suppress them.
21250 .option headers_remove transports list&!! unset
21251 .cindex "header lines" "removing"
21252 .cindex "transport" "header lines; removing"
21253 This option specifies a list of header names,
21254 colon-separated (by default, changeable in the usual way);
21255 these headers are omitted from the message as it is transported, as described
21256 in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
21258 Each list item is separately expanded.
21259 If the result of the expansion is an empty string, or if the expansion
21260 is forced to fail, no action is taken. Other expansion failures are treated as
21261 errors and cause the delivery to be deferred.
21263 Unlike most options, &%headers_remove%& can be specified multiple times
21264 for a transport; all listed headers are removed.
21266 &*Warning*&: Because of the separate expansion of the list items,
21267 items that contain a list separator must have it doubled.
21268 To avoid this, change the list separator (&<<SECTlistsepchange>>&).
21272 .option headers_rewrite transports string unset
21273 .cindex "transport" "header lines; rewriting"
21274 .cindex "rewriting" "at transport time"
21275 This option allows addresses in header lines to be rewritten at transport time,
21276 that is, as the message is being copied to its destination. The contents of the
21277 option are a colon-separated list of rewriting rules. Each rule is in exactly
21278 the same form as one of the general rewriting rules that are applied when a
21279 message is received. These are described in chapter &<<CHAPrewrite>>&. For
21282 headers_rewrite = a@b c@d f : \
21285 changes &'a@b'& into &'c@d'& in &'From:'& header lines, and &'x@y'& into
21286 &'w@z'& in all address-bearing header lines. The rules are applied to the
21287 header lines just before they are written out at transport time, so they affect
21288 only those copies of the message that pass through the transport. However, only
21289 the message's original header lines, and any that were added by a system
21290 filter, are rewritten. If a router or transport adds header lines, they are not
21291 affected by this option. These rewriting rules are &'not'& applied to the
21292 envelope. You can change the return path using &%return_path%&, but you cannot
21293 change envelope recipients at this time.
21296 .option home_directory transports string&!! unset
21297 .cindex "transport" "home directory for"
21299 This option specifies a home directory setting for a local transport,
21300 overriding any value that may be set by the router. The home directory is
21301 placed in &$home$& while expanding the transport's private options. It is also
21302 used as the current directory if no current directory is set by the
21303 &%current_directory%& option on the transport or the
21304 &%transport_current_directory%& option on the router. If the expansion fails
21305 for any reason, including forced failure, an error is logged, and delivery is
21309 .option initgroups transports boolean false
21310 .cindex "additional groups"
21311 .cindex "groups" "additional"
21312 .cindex "transport" "group; additional"
21313 If this option is true and the uid for the delivery process is provided by the
21314 transport, the &[initgroups()]& function is called when running the transport
21315 to ensure that any additional groups associated with the uid are set up.
21318 .option max_parallel transports integer&!! unset
21319 .cindex limit "transport parallelism"
21320 .cindex transport "parallel processes"
21321 .cindex transport "concurrency limit"
21322 .cindex "delivery" "parallelism for transport"
21323 If this option is set and expands to an integer greater than zero
21324 it limits the number of concurrent runs of the transport.
21325 The control does not apply to shadow transports.
21327 .cindex "hints database" "transport concurrency control"
21328 Exim implements this control by means of a hints database in which a record is
21329 incremented whenever a transport process is being created. The record
21330 is decremented and possibly removed when the process terminates.
21331 Obviously there is scope for
21332 records to get left lying around if there is a system or program crash. To
21333 guard against this, Exim ignores any records that are more than six hours old.
21335 If you use this option, you should also arrange to delete the
21336 relevant hints database whenever your system reboots. The names of the files
21337 start with &_misc_& and they are kept in the &_spool/db_& directory. There
21338 may be one or two files, depending on the type of DBM in use. The same files
21339 are used for ETRN and smtp transport serialization.
21342 .option message_size_limit transports string&!! 0
21343 .cindex "limit" "message size per transport"
21344 .cindex "size" "of message, limit"
21345 .cindex "transport" "message size; limiting"
21346 This option controls the size of messages passed through the transport. It is
21347 expanded before use; the result of the expansion must be a sequence of decimal
21348 digits, optionally followed by K or M. If the expansion fails for any reason,
21349 including forced failure, or if the result is not of the required form,
21350 delivery is deferred. If the value is greater than zero and the size of a
21351 message exceeds this limit, the address is failed. If there is any chance that
21352 the resulting bounce message could be routed to the same transport, you should
21353 ensure that &%return_size_limit%& is less than the transport's
21354 &%message_size_limit%&, as otherwise the bounce message will fail to get
21359 .option rcpt_include_affixes transports boolean false
21360 .cindex "prefix" "for local part, including in envelope"
21361 .cindex "suffix for local part" "including in envelope"
21362 .cindex "local part" "prefix"
21363 .cindex "local part" "suffix"
21364 When this option is false (the default), and an address that has had any
21365 affixes (prefixes or suffixes) removed from the local part is delivered by any
21366 form of SMTP or LMTP, the affixes are not included. For example, if a router
21369 local_part_prefix = *-
21371 routes the address &'abc-xyz@some.domain'& to an SMTP transport, the envelope
21374 RCPT TO:<xyz@some.domain>
21376 This is also the case when an ACL-time callout is being used to verify a
21377 recipient address. However, if &%rcpt_include_affixes%& is set true, the
21378 whole local part is included in the RCPT command. This option applies to BSMTP
21379 deliveries by the &(appendfile)& and &(pipe)& transports as well as to the
21380 &(lmtp)& and &(smtp)& transports.
21383 .option retry_use_local_part transports boolean "see below"
21384 .cindex "hints database" "retry keys"
21385 When a delivery suffers a temporary failure, a retry record is created
21386 in Exim's hints database. For remote deliveries, the key for the retry record
21387 is based on the name and/or IP address of the failing remote host. For local
21388 deliveries, the key is normally the entire address, including both the local
21389 part and the domain. This is suitable for most common cases of local delivery
21390 temporary failure &-- for example, exceeding a mailbox quota should delay only
21391 deliveries to that mailbox, not to the whole domain.
21393 However, in some special cases you may want to treat a temporary local delivery
21394 as a failure associated with the domain, and not with a particular local part.
21395 (For example, if you are storing all mail for some domain in files.) You can do
21396 this by setting &%retry_use_local_part%& false.
21398 For all the local transports, its default value is true. For remote transports,
21399 the default value is false for tidiness, but changing the value has no effect
21400 on a remote transport in the current implementation.
21403 .option return_path transports string&!! unset
21404 .cindex "envelope sender"
21405 .cindex "transport" "return path; changing"
21406 .cindex "return path" "changing in transport"
21407 If this option is set, the string is expanded at transport time and replaces
21408 the existing return path (envelope sender) value in the copy of the message
21409 that is being delivered. An empty return path is permitted. This feature is
21410 designed for remote deliveries, where the value of this option is used in the
21411 SMTP MAIL command. If you set &%return_path%& for a local transport, the
21412 only effect is to change the address that is placed in the &'Return-path:'&
21413 header line, if one is added to the message (see the next option).
21415 &*Note:*& A changed return path is not logged unless you add
21416 &%return_path_on_delivery%& to the log selector.
21418 .vindex "&$return_path$&"
21419 The expansion can refer to the existing value via &$return_path$&. This is
21420 either the message's envelope sender, or an address set by the
21421 &%errors_to%& option on a router. If the expansion is forced to fail, no
21422 replacement occurs; if it fails for another reason, delivery is deferred. This
21423 option can be used to support VERP (Variable Envelope Return Paths) &-- see
21424 section &<<SECTverp>>&.
21426 &*Note*&: If a delivery error is detected locally, including the case when a
21427 remote server rejects a message at SMTP time, the bounce message is not sent to
21428 the value of this option. It is sent to the previously set errors address.
21429 This defaults to the incoming sender address, but can be changed by setting
21430 &%errors_to%& in a router.
21434 .option return_path_add transports boolean false
21435 .cindex "&'Return-path:'& header line"
21436 If this option is true, a &'Return-path:'& header is added to the message.
21437 Although the return path is normally available in the prefix line of BSD
21438 mailboxes, this is commonly not displayed by MUAs, and so the user does not
21439 have easy access to it.
21441 RFC 2821 states that the &'Return-path:'& header is added to a message &"when
21442 the delivery SMTP server makes the final delivery"&. This implies that this
21443 header should not be present in incoming messages. Exim has a configuration
21444 option, &%return_path_remove%&, which requests removal of this header from
21445 incoming messages, so that delivered messages can safely be resent to other
21449 .option shadow_condition transports string&!! unset
21450 See &%shadow_transport%& below.
21453 .option shadow_transport transports string unset
21454 .cindex "shadow transport"
21455 .cindex "transport" "shadow"
21456 A local transport may set the &%shadow_transport%& option to the name of
21457 another local transport. Shadow remote transports are not supported.
21459 Whenever a delivery to the main transport succeeds, and either
21460 &%shadow_condition%& is unset, or its expansion does not result in the empty
21461 string or one of the strings &"0"& or &"no"& or &"false"&, the message is also
21462 passed to the shadow transport, with the same delivery address or addresses. If
21463 expansion fails, no action is taken except that non-forced expansion failures
21464 cause a log line to be written.
21466 The result of the shadow transport is discarded and does not affect the
21467 subsequent processing of the message. Only a single level of shadowing is
21468 provided; the &%shadow_transport%& option is ignored on any transport when it
21469 is running as a shadow. Options concerned with output from pipes are also
21470 ignored. The log line for the successful delivery has an item added on the end,
21473 ST=<shadow transport name>
21475 If the shadow transport did not succeed, the error message is put in
21476 parentheses afterwards. Shadow transports can be used for a number of different
21477 purposes, including keeping more detailed log information than Exim normally
21478 provides, and implementing automatic acknowledgment policies based on message
21479 headers that some sites insist on.
21482 .option transport_filter transports string&!! unset
21483 .cindex "transport" "filter"
21484 .cindex "filter" "transport filter"
21485 This option sets up a filtering (in the Unix shell sense) process for messages
21486 at transport time. It should not be confused with mail filtering as set up by
21487 individual users or via a system filter.
21488 If unset, or expanding to an empty string, no filtering is done.
21490 When the message is about to be written out, the command specified by
21491 &%transport_filter%& is started up in a separate, parallel process, and
21492 the entire message, including the header lines, is passed to it on its standard
21493 input (this in fact is done from a third process, to avoid deadlock). The
21494 command must be specified as an absolute path.
21496 The lines of the message that are written to the transport filter are
21497 terminated by newline (&"\n"&). The message is passed to the filter before any
21498 SMTP-specific processing, such as turning &"\n"& into &"\r\n"& and escaping
21499 lines beginning with a dot, and also before any processing implied by the
21500 settings of &%check_string%& and &%escape_string%& in the &(appendfile)& or
21501 &(pipe)& transports.
21503 The standard error for the filter process is set to the same destination as its
21504 standard output; this is read and written to the message's ultimate
21505 destination. The process that writes the message to the filter, the
21506 filter itself, and the original process that reads the result and delivers it
21507 are all run in parallel, like a shell pipeline.
21509 The filter can perform any transformations it likes, but of course should take
21510 care not to break RFC 2822 syntax. Exim does not check the result, except to
21511 test for a final newline when SMTP is in use. All messages transmitted over
21512 SMTP must end with a newline, so Exim supplies one if it is missing.
21514 .cindex "content scanning" "per user"
21515 A transport filter can be used to provide content-scanning on a per-user basis
21516 at delivery time if the only required effect of the scan is to modify the
21517 message. For example, a content scan could insert a new header line containing
21518 a spam score. This could be interpreted by a filter in the user's MUA. It is
21519 not possible to discard a message at this stage.
21521 .cindex "SMTP" "SIZE"
21522 A problem might arise if the filter increases the size of a message that is
21523 being sent down an SMTP connection. If the receiving SMTP server has indicated
21524 support for the SIZE parameter, Exim will have sent the size of the message
21525 at the start of the SMTP session. If what is actually sent is substantially
21526 more, the server might reject the message. This can be worked round by setting
21527 the &%size_addition%& option on the &(smtp)& transport, either to allow for
21528 additions to the message, or to disable the use of SIZE altogether.
21530 .vindex "&$pipe_addresses$&"
21531 The value of the &%transport_filter%& option is the command string for starting
21532 the filter, which is run directly from Exim, not under a shell. The string is
21533 parsed by Exim in the same way as a command string for the &(pipe)& transport:
21534 Exim breaks it up into arguments and then expands each argument separately (see
21535 section &<<SECThowcommandrun>>&). Any kind of expansion failure causes delivery
21536 to be deferred. The special argument &$pipe_addresses$& is replaced by a number
21537 of arguments, one for each address that applies to this delivery. (This isn't
21538 an ideal name for this feature here, but as it was already implemented for the
21539 &(pipe)& transport, it seemed sensible not to change it.)
21542 .vindex "&$host_address$&"
21543 The expansion variables &$host$& and &$host_address$& are available when the
21544 transport is a remote one. They contain the name and IP address of the host to
21545 which the message is being sent. For example:
21547 transport_filter = /some/directory/transport-filter.pl \
21548 $host $host_address $sender_address $pipe_addresses
21551 Two problems arise if you want to use more complicated expansion items to
21552 generate transport filter commands, both of which due to the fact that the
21553 command is split up &'before'& expansion.
21555 If an expansion item contains white space, you must quote it, so that it is all
21556 part of the same command item. If the entire option setting is one such
21557 expansion item, you have to take care what kind of quoting you use. For
21560 transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}'
21562 This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and
21563 &(/bin/cmd2)& otherwise. If double quotes had been used, they would have been
21564 stripped by Exim when it read the option's value. When the value is used, if
21565 the single quotes were missing, the line would be split into two items,
21566 &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when
21567 Exim tried to expand the first one.
21569 Except for the special case of &$pipe_addresses$& that is mentioned above, an
21570 expansion cannot generate multiple arguments, or a command name followed by
21571 arguments. Consider this example:
21573 transport_filter = ${lookup{$host}lsearch{/a/file}\
21574 {$value}{/bin/cat}}
21576 The result of the lookup is interpreted as the name of the command, even
21577 if it contains white space. The simplest way round this is to use a shell:
21579 transport_filter = /bin/sh -c ${lookup{$host}lsearch{/a/file}\
21580 {$value}{/bin/cat}}
21584 The filter process is run under the same uid and gid as the normal delivery.
21585 For remote deliveries this is the Exim uid/gid by default. The command should
21586 normally yield a zero return code. Transport filters are not supposed to fail.
21587 A non-zero code is taken to mean that the transport filter encountered some
21588 serious problem. Delivery of the message is deferred; the message remains on
21589 the queue and is tried again later. It is not possible to cause a message to be
21590 bounced from a transport filter.
21592 If a transport filter is set on an autoreply transport, the original message is
21593 passed through the filter as it is being copied into the newly generated
21594 message, which happens if the &%return_message%& option is set.
21597 .option transport_filter_timeout transports time 5m
21598 .cindex "transport" "filter, timeout"
21599 When Exim is reading the output of a transport filter, it applies a timeout
21600 that can be set by this option. Exceeding the timeout is normally treated as a
21601 temporary delivery failure. However, if a transport filter is used with a
21602 &(pipe)& transport, a timeout in the transport filter is treated in the same
21603 way as a timeout in the pipe command itself. By default, a timeout is a hard
21604 error, but if the &(pipe)& transport's &%timeout_defer%& option is set true, it
21605 becomes a temporary error.
21608 .option user transports string&!! "Exim user"
21609 .cindex "uid (user id)" "local delivery"
21610 .cindex "transport" "user, specifying"
21611 This option specifies the user under whose uid the delivery process is to be
21612 run, overriding any uid that may have been set by the router. If the user is
21613 given as a name, the uid is looked up from the password data, and the
21614 associated group is taken as the value of the gid to be used if the &%group%&
21617 For deliveries that use local transports, a user and group are normally
21618 specified explicitly or implicitly (for example, as a result of
21619 &%check_local_user%&) by the router or transport.
21621 .cindex "hints database" "access by remote transport"
21622 For remote transports, you should leave this option unset unless you really are
21623 sure you know what you are doing. When a remote transport is running, it needs
21624 to be able to access Exim's hints databases, because each host may have its own
21626 .ecindex IIDgenoptra1
21627 .ecindex IIDgenoptra2
21628 .ecindex IIDgenoptra3
21635 . ////////////////////////////////////////////////////////////////////////////
21636 . ////////////////////////////////////////////////////////////////////////////
21638 .chapter "Address batching in local transports" "CHAPbatching" &&&
21640 .cindex "transport" "local; address batching in"
21641 The only remote transport (&(smtp)&) is normally configured to handle more than
21642 one address at a time, so that when several addresses are routed to the same
21643 remote host, just one copy of the message is sent. Local transports, however,
21644 normally handle one address at a time. That is, a separate instance of the
21645 transport is run for each address that is routed to the transport. A separate
21646 copy of the message is delivered each time.
21648 .cindex "batched local delivery"
21649 .oindex "&%batch_max%&"
21650 .oindex "&%batch_id%&"
21651 In special cases, it may be desirable to handle several addresses at once in a
21652 local transport, for example:
21655 In an &(appendfile)& transport, when storing messages in files for later
21656 delivery by some other means, a single copy of the message with multiple
21657 recipients saves space.
21659 In an &(lmtp)& transport, when delivering over &"local SMTP"& to some process,
21660 a single copy saves time, and is the normal way LMTP is expected to work.
21662 In a &(pipe)& transport, when passing the message
21663 to a scanner program or
21664 to some other delivery mechanism such as UUCP, multiple recipients may be
21668 These three local transports all have the same options for controlling multiple
21669 (&"batched"&) deliveries, namely &%batch_max%& and &%batch_id%&. To save
21670 repeating the information for each transport, these options are described here.
21672 The &%batch_max%& option specifies the maximum number of addresses that can be
21673 delivered together in a single run of the transport. Its default value is one
21674 (no batching). When more than one address is routed to a transport that has a
21675 &%batch_max%& value greater than one, the addresses are delivered in a batch
21676 (that is, in a single run of the transport with multiple recipients), subject
21677 to certain conditions:
21680 .vindex "&$local_part$&"
21681 If any of the transport's options contain a reference to &$local_part$&, no
21682 batching is possible.
21684 .vindex "&$domain$&"
21685 If any of the transport's options contain a reference to &$domain$&, only
21686 addresses with the same domain are batched.
21688 .cindex "customizing" "batching condition"
21689 If &%batch_id%& is set, it is expanded for each address, and only those
21690 addresses with the same expanded value are batched. This allows you to specify
21691 customized batching conditions. Failure of the expansion for any reason,
21692 including forced failure, disables batching, but it does not stop the delivery
21695 Batched addresses must also have the same errors address (where to send
21696 delivery errors), the same header additions and removals, the same user and
21697 group for the transport, and if a host list is present, the first host must
21701 In the case of the &(appendfile)& and &(pipe)& transports, batching applies
21702 both when the file or pipe command is specified in the transport, and when it
21703 is specified by a &(redirect)& router, but all the batched addresses must of
21704 course be routed to the same file or pipe command. These two transports have an
21705 option called &%use_bsmtp%&, which causes them to deliver the message in
21706 &"batched SMTP"& format, with the envelope represented as SMTP commands. The
21707 &%check_string%& and &%escape_string%& options are forced to the values
21710 escape_string = ".."
21712 when batched SMTP is in use. A full description of the batch SMTP mechanism is
21713 given in section &<<SECTbatchSMTP>>&. The &(lmtp)& transport does not have a
21714 &%use_bsmtp%& option, because it always delivers using the SMTP protocol.
21716 .cindex "&'Envelope-to:'& header line"
21717 If the generic &%envelope_to_add%& option is set for a batching transport, the
21718 &'Envelope-to:'& header that is added to the message contains all the addresses
21719 that are being processed together. If you are using a batching &(appendfile)&
21720 transport without &%use_bsmtp%&, the only way to preserve the recipient
21721 addresses is to set the &%envelope_to_add%& option.
21723 .cindex "&(pipe)& transport" "with multiple addresses"
21724 .vindex "&$pipe_addresses$&"
21725 If you are using a &(pipe)& transport without BSMTP, and setting the
21726 transport's &%command%& option, you can include &$pipe_addresses$& as part of
21727 the command. This is not a true variable; it is a bit of magic that causes each
21728 of the recipient addresses to be inserted into the command as a separate
21729 argument. This provides a way of accessing all the addresses that are being
21730 delivered in the batch. &*Note:*& This is not possible for pipe commands that
21731 are specified by a &(redirect)& router.
21736 . ////////////////////////////////////////////////////////////////////////////
21737 . ////////////////////////////////////////////////////////////////////////////
21739 .chapter "The appendfile transport" "CHAPappendfile"
21740 .scindex IIDapptra1 "&(appendfile)& transport"
21741 .scindex IIDapptra2 "transports" "&(appendfile)&"
21742 .cindex "directory creation"
21743 .cindex "creating directories"
21744 The &(appendfile)& transport delivers a message by appending it to an existing
21745 file, or by creating an entirely new file in a specified directory. Single
21746 files to which messages are appended can be in the traditional Unix mailbox
21747 format, or optionally in the MBX format supported by the Pine MUA and
21748 University of Washington IMAP daemon, &'inter alia'&. When each message is
21749 being delivered as a separate file, &"maildir"& format can optionally be used
21750 to give added protection against failures that happen part-way through the
21751 delivery. A third form of separate-file delivery known as &"mailstore"& is also
21752 supported. For all file formats, Exim attempts to create as many levels of
21753 directory as necessary, provided that &%create_directory%& is set.
21755 The code for the optional formats is not included in the Exim binary by
21756 default. It is necessary to set SUPPORT_MBX, SUPPORT_MAILDIR and/or
21757 SUPPORT_MAILSTORE in &_Local/Makefile_& to have the appropriate code
21760 .cindex "quota" "system"
21761 Exim recognizes system quota errors, and generates an appropriate message. Exim
21762 also supports its own quota control within the transport, for use when the
21763 system facility is unavailable or cannot be used for some reason.
21765 If there is an error while appending to a file (for example, quota exceeded or
21766 partition filled), Exim attempts to reset the file's length and last
21767 modification time back to what they were before. If there is an error while
21768 creating an entirely new file, the new file is removed.
21770 Before appending to a file, a number of security checks are made, and the
21771 file is locked. A detailed description is given below, after the list of
21774 The &(appendfile)& transport is most commonly used for local deliveries to
21775 users' mailboxes. However, it can also be used as a pseudo-remote transport for
21776 putting messages into files for remote delivery by some means other than Exim.
21777 &"Batch SMTP"& format is often used in this case (see the &%use_bsmtp%&
21782 .section "The file and directory options" "SECTfildiropt"
21783 The &%file%& option specifies a single file, to which the message is appended;
21784 the &%directory%& option specifies a directory, in which a new file containing
21785 the message is created. Only one of these two options can be set, and for
21786 normal deliveries to mailboxes, one of them &'must'& be set.
21788 .vindex "&$address_file$&"
21789 .vindex "&$local_part$&"
21790 However, &(appendfile)& is also used for delivering messages to files or
21791 directories whose names (or parts of names) are obtained from alias,
21792 forwarding, or filtering operations (for example, a &%save%& command in a
21793 user's Exim filter). When such a transport is running, &$local_part$& contains
21794 the local part that was aliased or forwarded, and &$address_file$& contains the
21795 name (or partial name) of the file or directory generated by the redirection
21796 operation. There are two cases:
21799 If neither &%file%& nor &%directory%& is set, the redirection operation
21800 must specify an absolute path (one that begins with &`/`&). This is the most
21801 common case when users with local accounts use filtering to sort mail into
21802 different folders. See for example, the &(address_file)& transport in the
21803 default configuration. If the path ends with a slash, it is assumed to be the
21804 name of a directory. A delivery to a directory can also be forced by setting
21805 &%maildir_format%& or &%mailstore_format%&.
21807 If &%file%& or &%directory%& is set for a delivery from a redirection, it is
21808 used to determine the file or directory name for the delivery. Normally, the
21809 contents of &$address_file$& are used in some way in the string expansion.
21813 .cindex "Sieve filter" "configuring &(appendfile)&"
21814 .cindex "Sieve filter" "relative mailbox path handling"
21815 As an example of the second case, consider an environment where users do not
21816 have home directories. They may be permitted to use Exim filter commands of the
21821 or Sieve filter commands of the form:
21823 require "fileinto";
21824 fileinto "folder23";
21826 In this situation, the expansion of &%file%& or &%directory%& in the transport
21827 must transform the relative path into an appropriate absolute file name. In the
21828 case of Sieve filters, the name &'inbox'& must be handled. It is the name that
21829 is used as a result of a &"keep"& action in the filter. This example shows one
21830 way of handling this requirement:
21832 file = ${if eq{$address_file}{inbox} \
21833 {/var/mail/$local_part} \
21834 {${if eq{${substr_0_1:$address_file}}{/} \
21836 {$home/mail/$address_file} \
21840 With this setting of &%file%&, &'inbox'& refers to the standard mailbox
21841 location, absolute paths are used without change, and other folders are in the
21842 &_mail_& directory within the home directory.
21844 &*Note 1*&: While processing an Exim filter, a relative path such as
21845 &_folder23_& is turned into an absolute path if a home directory is known to
21846 the router. In particular, this is the case if &%check_local_user%& is set. If
21847 you want to prevent this happening at routing time, you can set
21848 &%router_home_directory%& empty. This forces the router to pass the relative
21849 path to the transport.
21851 &*Note 2*&: An absolute path in &$address_file$& is not treated specially;
21852 the &%file%& or &%directory%& option is still used if it is set.
21857 .section "Private options for appendfile" "SECID134"
21858 .cindex "options" "&(appendfile)& transport"
21862 .option allow_fifo appendfile boolean false
21863 .cindex "fifo (named pipe)"
21864 .cindex "named pipe (fifo)"
21865 .cindex "pipe" "named (fifo)"
21866 Setting this option permits delivery to named pipes (FIFOs) as well as to
21867 regular files. If no process is reading the named pipe at delivery time, the
21868 delivery is deferred.
21871 .option allow_symlink appendfile boolean false
21872 .cindex "symbolic link" "to mailbox"
21873 .cindex "mailbox" "symbolic link"
21874 By default, &(appendfile)& will not deliver if the path name for the file is
21875 that of a symbolic link. Setting this option relaxes that constraint, but there
21876 are security issues involved in the use of symbolic links. Be sure you know
21877 what you are doing if you set this. Details of exactly what this option affects
21878 are included in the discussion which follows this list of options.
21881 .option batch_id appendfile string&!! unset
21882 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21883 However, batching is automatically disabled for &(appendfile)& deliveries that
21884 happen as a result of forwarding or aliasing or other redirection directly to a
21888 .option batch_max appendfile integer 1
21889 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
21892 .option check_group appendfile boolean false
21893 When this option is set, the group owner of the file defined by the &%file%&
21894 option is checked to see that it is the same as the group under which the
21895 delivery process is running. The default setting is false because the default
21896 file mode is 0600, which means that the group is irrelevant.
21899 .option check_owner appendfile boolean true
21900 When this option is set, the owner of the file defined by the &%file%& option
21901 is checked to ensure that it is the same as the user under which the delivery
21902 process is running.
21905 .option check_string appendfile string "see below"
21906 .cindex "&""From""& line"
21907 As &(appendfile)& writes the message, the start of each line is tested for
21908 matching &%check_string%&, and if it does, the initial matching characters are
21909 replaced by the contents of &%escape_string%&. The value of &%check_string%& is
21910 a literal string, not a regular expression, and the case of any letters it
21911 contains is significant.
21913 If &%use_bsmtp%& is set the values of &%check_string%& and &%escape_string%&
21914 are forced to &"."& and &".."& respectively, and any settings in the
21915 configuration are ignored. Otherwise, they default to &"From&~"& and
21916 &">From&~"& when the &%file%& option is set, and unset when any of the
21917 &%directory%&, &%maildir%&, or &%mailstore%& options are set.
21919 The default settings, along with &%message_prefix%& and &%message_suffix%&, are
21920 suitable for traditional &"BSD"& mailboxes, where a line beginning with
21921 &"From&~"& indicates the start of a new message. All four options need changing
21922 if another format is used. For example, to deliver to mailboxes in MMDF format:
21923 .cindex "MMDF format mailbox"
21924 .cindex "mailbox" "MMDF format"
21926 check_string = "\1\1\1\1\n"
21927 escape_string = "\1\1\1\1 \n"
21928 message_prefix = "\1\1\1\1\n"
21929 message_suffix = "\1\1\1\1\n"
21931 .option create_directory appendfile boolean true
21932 .cindex "directory creation"
21933 When this option is true, Exim attempts to create any missing superior
21934 directories for the file that it is about to write. A created directory's mode
21935 is given by the &%directory_mode%& option.
21937 The group ownership of a newly created directory is highly dependent on the
21938 operating system (and possibly the file system) that is being used. For
21939 example, in Solaris, if the parent directory has the setgid bit set, its group
21940 is propagated to the child; if not, the currently set group is used. However,
21941 in FreeBSD, the parent's group is always used.
21945 .option create_file appendfile string anywhere
21946 This option constrains the location of files and directories that are created
21947 by this transport. It applies to files defined by the &%file%& option and
21948 directories defined by the &%directory%& option. In the case of maildir
21949 delivery, it applies to the top level directory, not the maildir directories
21952 The option must be set to one of the words &"anywhere"&, &"inhome"&, or
21953 &"belowhome"&. In the second and third cases, a home directory must have been
21954 set for the transport. This option is not useful when an explicit file name is
21955 given for normal mailbox deliveries. It is intended for the case when file
21956 names are generated from users' &_.forward_& files. These are usually handled
21957 by an &(appendfile)& transport called &%address_file%&. See also
21958 &%file_must_exist%&.
21961 .option directory appendfile string&!! unset
21962 This option is mutually exclusive with the &%file%& option, but one of &%file%&
21963 or &%directory%& must be set, unless the delivery is the direct result of a
21964 redirection (see section &<<SECTfildiropt>>&).
21966 When &%directory%& is set, the string is expanded, and the message is delivered
21967 into a new file or files in or below the given directory, instead of being
21968 appended to a single mailbox file. A number of different formats are provided
21969 (see &%maildir_format%& and &%mailstore_format%&), and see section
21970 &<<SECTopdir>>& for further details of this form of delivery.
21973 .option directory_file appendfile string&!! "see below"
21975 .vindex "&$inode$&"
21976 When &%directory%& is set, but neither &%maildir_format%& nor
21977 &%mailstore_format%& is set, &(appendfile)& delivers each message into a file
21978 whose name is obtained by expanding this string. The default value is:
21980 q${base62:$tod_epoch}-$inode
21982 This generates a unique name from the current time, in base 62 form, and the
21983 inode of the file. The variable &$inode$& is available only when expanding this
21987 .option directory_mode appendfile "octal integer" 0700
21988 If &(appendfile)& creates any directories as a result of the
21989 &%create_directory%& option, their mode is specified by this option.
21992 .option escape_string appendfile string "see description"
21993 See &%check_string%& above.
21996 .option file appendfile string&!! unset
21997 This option is mutually exclusive with the &%directory%& option, but one of
21998 &%file%& or &%directory%& must be set, unless the delivery is the direct result
21999 of a redirection (see section &<<SECTfildiropt>>&). The &%file%& option
22000 specifies a single file, to which the message is appended. One or more of
22001 &%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
22004 .cindex "NFS" "lock file"
22005 .cindex "locking files"
22006 .cindex "lock files"
22007 If you are using more than one host to deliver over NFS into the same
22008 mailboxes, you should always use lock files.
22010 The string value is expanded for each delivery, and must yield an absolute
22011 path. The most common settings of this option are variations on one of these
22014 file = /var/spool/mail/$local_part
22015 file = /home/$local_part/inbox
22018 .cindex "&""sticky""& bit"
22019 In the first example, all deliveries are done into the same directory. If Exim
22020 is configured to use lock files (see &%use_lockfile%& below) it must be able to
22021 create a file in the directory, so the &"sticky"& bit must be turned on for
22022 deliveries to be possible, or alternatively the &%group%& option can be used to
22023 run the delivery under a group id which has write access to the directory.
22027 .option file_format appendfile string unset
22028 .cindex "file" "mailbox; checking existing format"
22029 This option requests the transport to check the format of an existing file
22030 before adding to it. The check consists of matching a specific string at the
22031 start of the file. The value of the option consists of an even number of
22032 colon-separated strings. The first of each pair is the test string, and the
22033 second is the name of a transport. If the transport associated with a matched
22034 string is not the current transport, control is passed over to the other
22035 transport. For example, suppose the standard &(local_delivery)& transport has
22038 file_format = "From : local_delivery :\
22039 \1\1\1\1\n : local_mmdf_delivery"
22041 Mailboxes that begin with &"From"& are still handled by this transport, but if
22042 a mailbox begins with four binary ones followed by a newline, control is passed
22043 to a transport called &%local_mmdf_delivery%&, which presumably is configured
22044 to do the delivery in MMDF format. If a mailbox does not exist or is empty, it
22045 is assumed to match the current transport. If the start of a mailbox doesn't
22046 match any string, or if the transport named for a given string is not defined,
22047 delivery is deferred.
22050 .option file_must_exist appendfile boolean false
22051 If this option is true, the file specified by the &%file%& option must exist.
22052 A temporary error occurs if it does not, causing delivery to be deferred.
22053 If this option is false, the file is created if it does not exist.
22056 .option lock_fcntl_timeout appendfile time 0s
22057 .cindex "timeout" "mailbox locking"
22058 .cindex "mailbox" "locking, blocking and non-blocking"
22059 .cindex "locking files"
22060 By default, the &(appendfile)& transport uses non-blocking calls to &[fcntl()]&
22061 when locking an open mailbox file. If the call fails, the delivery process
22062 sleeps for &%lock_interval%& and tries again, up to &%lock_retries%& times.
22063 Non-blocking calls are used so that the file is not kept open during the wait
22064 for the lock; the reason for this is to make it as safe as possible for
22065 deliveries over NFS in the case when processes might be accessing an NFS
22066 mailbox without using a lock file. This should not be done, but
22067 misunderstandings and hence misconfigurations are not unknown.
22069 On a busy system, however, the performance of a non-blocking lock approach is
22070 not as good as using a blocking lock with a timeout. In this case, the waiting
22071 is done inside the system call, and Exim's delivery process acquires the lock
22072 and can proceed as soon as the previous lock holder releases it.
22074 If &%lock_fcntl_timeout%& is set to a non-zero time, blocking locks, with that
22075 timeout, are used. There may still be some retrying: the maximum number of
22078 (lock_retries * lock_interval) / lock_fcntl_timeout
22080 rounded up to the next whole number. In other words, the total time during
22081 which &(appendfile)& is trying to get a lock is roughly the same, unless
22082 &%lock_fcntl_timeout%& is set very large.
22084 You should consider setting this option if you are getting a lot of delayed
22085 local deliveries because of errors of the form
22087 failed to lock mailbox /some/file (fcntl)
22090 .option lock_flock_timeout appendfile time 0s
22091 This timeout applies to file locking when using &[flock()]& (see
22092 &%use_flock%&); the timeout operates in a similar manner to
22093 &%lock_fcntl_timeout%&.
22096 .option lock_interval appendfile time 3s
22097 This specifies the time to wait between attempts to lock the file. See below
22098 for details of locking.
22101 .option lock_retries appendfile integer 10
22102 This specifies the maximum number of attempts to lock the file. A value of zero
22103 is treated as 1. See below for details of locking.
22106 .option lockfile_mode appendfile "octal integer" 0600
22107 This specifies the mode of the created lock file, when a lock file is being
22108 used (see &%use_lockfile%& and &%use_mbx_lock%&).
22111 .option lockfile_timeout appendfile time 30m
22112 .cindex "timeout" "mailbox locking"
22113 When a lock file is being used (see &%use_lockfile%&), if a lock file already
22114 exists and is older than this value, it is assumed to have been left behind by
22115 accident, and Exim attempts to remove it.
22118 .option mailbox_filecount appendfile string&!! unset
22119 .cindex "mailbox" "specifying size of"
22120 .cindex "size" "of mailbox"
22121 If this option is set, it is expanded, and the result is taken as the current
22122 number of files in the mailbox. It must be a decimal number, optionally
22123 followed by K or M. This provides a way of obtaining this information from an
22124 external source that maintains the data.
22127 .option mailbox_size appendfile string&!! unset
22128 .cindex "mailbox" "specifying size of"
22129 .cindex "size" "of mailbox"
22130 If this option is set, it is expanded, and the result is taken as the current
22131 size the mailbox. It must be a decimal number, optionally followed by K or M.
22132 This provides a way of obtaining this information from an external source that
22133 maintains the data. This is likely to be helpful for maildir deliveries where
22134 it is computationally expensive to compute the size of a mailbox.
22138 .option maildir_format appendfile boolean false
22139 .cindex "maildir format" "specifying"
22140 If this option is set with the &%directory%& option, the delivery is into a new
22141 file, in the &"maildir"& format that is used by other mail software. When the
22142 transport is activated directly from a &(redirect)& router (for example, the
22143 &(address_file)& transport in the default configuration), setting
22144 &%maildir_format%& causes the path received from the router to be treated as a
22145 directory, whether or not it ends with &`/`&. This option is available only if
22146 SUPPORT_MAILDIR is present in &_Local/Makefile_&. See section
22147 &<<SECTmaildirdelivery>>& below for further details.
22150 .option maildir_quota_directory_regex appendfile string "See below"
22151 .cindex "maildir format" "quota; directories included in"
22152 .cindex "quota" "maildir; directories included in"
22153 This option is relevant only when &%maildir_use_size_file%& is set. It defines
22154 a regular expression for specifying directories, relative to the quota
22155 directory (see &%quota_directory%&), that should be included in the quota
22156 calculation. The default value is:
22158 maildir_quota_directory_regex = ^(?:cur|new|\..*)$
22160 This includes the &_cur_& and &_new_& directories, and any maildir++ folders
22161 (directories whose names begin with a dot). If you want to exclude the
22163 folder from the count (as some sites do), you need to change this setting to
22165 maildir_quota_directory_regex = ^(?:cur|new|\.(?!Trash).*)$
22167 This uses a negative lookahead in the regular expression to exclude the
22168 directory whose name is &_.Trash_&. When a directory is excluded from quota
22169 calculations, quota processing is bypassed for any messages that are delivered
22170 directly into that directory.
22173 .option maildir_retries appendfile integer 10
22174 This option specifies the number of times to retry when writing a file in
22175 &"maildir"& format. See section &<<SECTmaildirdelivery>>& below.
22178 .option maildir_tag appendfile string&!! unset
22179 This option applies only to deliveries in maildir format, and is described in
22180 section &<<SECTmaildirdelivery>>& below.
22183 .option maildir_use_size_file appendfile&!! boolean false
22184 .cindex "maildir format" "&_maildirsize_& file"
22185 The result of string expansion for this option must be a valid boolean value.
22186 If it is true, it enables support for &_maildirsize_& files. Exim
22187 creates a &_maildirsize_& file in a maildir if one does not exist, taking the
22188 quota from the &%quota%& option of the transport. If &%quota%& is unset, the
22189 value is zero. See &%maildir_quota_directory_regex%& above and section
22190 &<<SECTmaildirdelivery>>& below for further details.
22192 .option maildirfolder_create_regex appendfile string unset
22193 .cindex "maildir format" "&_maildirfolder_& file"
22194 .cindex "&_maildirfolder_&, creating"
22195 The value of this option is a regular expression. If it is unset, it has no
22196 effect. Otherwise, before a maildir delivery takes place, the pattern is
22197 matched against the name of the maildir directory, that is, the directory
22198 containing the &_new_& and &_tmp_& subdirectories that will be used for the
22199 delivery. If there is a match, Exim checks for the existence of a file called
22200 &_maildirfolder_& in the directory, and creates it if it does not exist.
22201 See section &<<SECTmaildirdelivery>>& for more details.
22204 .option mailstore_format appendfile boolean false
22205 .cindex "mailstore format" "specifying"
22206 If this option is set with the &%directory%& option, the delivery is into two
22207 new files in &"mailstore"& format. The option is available only if
22208 SUPPORT_MAILSTORE is present in &_Local/Makefile_&. See section &<<SECTopdir>>&
22209 below for further details.
22212 .option mailstore_prefix appendfile string&!! unset
22213 This option applies only to deliveries in mailstore format, and is described in
22214 section &<<SECTopdir>>& below.
22217 .option mailstore_suffix appendfile string&!! unset
22218 This option applies only to deliveries in mailstore format, and is described in
22219 section &<<SECTopdir>>& below.
22222 .option mbx_format appendfile boolean false
22223 .cindex "locking files"
22224 .cindex "file" "locking"
22225 .cindex "file" "MBX format"
22226 .cindex "MBX format, specifying"
22227 This option is available only if Exim has been compiled with SUPPORT_MBX
22228 set in &_Local/Makefile_&. If &%mbx_format%& is set with the &%file%& option,
22229 the message is appended to the mailbox file in MBX format instead of
22230 traditional Unix format. This format is supported by Pine4 and its associated
22231 IMAP and POP daemons, by means of the &'c-client'& library that they all use.
22233 &*Note*&: The &%message_prefix%& and &%message_suffix%& options are not
22234 automatically changed by the use of &%mbx_format%&. They should normally be set
22235 empty when using MBX format, so this option almost always appears in this
22242 If none of the locking options are mentioned in the configuration,
22243 &%use_mbx_lock%& is assumed and the other locking options default to false. It
22244 is possible to specify the other kinds of locking with &%mbx_format%&, but
22245 &%use_fcntl_lock%& and &%use_mbx_lock%& are mutually exclusive. MBX locking
22246 interworks with &'c-client'&, providing for shared access to the mailbox. It
22247 should not be used if any program that does not use this form of locking is
22248 going to access the mailbox, nor should it be used if the mailbox file is NFS
22249 mounted, because it works only when the mailbox is accessed from a single host.
22251 If you set &%use_fcntl_lock%& with an MBX-format mailbox, you cannot use
22252 the standard version of &'c-client'&, because as long as it has a mailbox open
22253 (this means for the whole of a Pine or IMAP session), Exim will not be able to
22254 append messages to it.
22257 .option message_prefix appendfile string&!! "see below"
22258 .cindex "&""From""& line"
22259 The string specified here is expanded and output at the start of every message.
22260 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
22261 in which case it is:
22263 message_prefix = "From ${if def:return_path{$return_path}\
22264 {MAILER-DAEMON}} $tod_bsdinbox\n"
22266 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22267 &`\n`& to &`\r\n`& in &%message_prefix%&.
22269 .option message_suffix appendfile string&!! "see below"
22270 The string specified here is expanded and output at the end of every message.
22271 The default is unset unless &%file%& is specified and &%use_bsmtp%& is not set,
22272 in which case it is a single newline character. The suffix can be suppressed by
22277 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
22278 &`\n`& to &`\r\n`& in &%message_suffix%&.
22280 .option mode appendfile "octal integer" 0600
22281 If the output file is created, it is given this mode. If it already exists and
22282 has wider permissions, they are reduced to this mode. If it has narrower
22283 permissions, an error occurs unless &%mode_fail_narrower%& is false. However,
22284 if the delivery is the result of a &%save%& command in a filter file specifying
22285 a particular mode, the mode of the output file is always forced to take that
22286 value, and this option is ignored.
22289 .option mode_fail_narrower appendfile boolean true
22290 This option applies in the case when an existing mailbox file has a narrower
22291 mode than that specified by the &%mode%& option. If &%mode_fail_narrower%& is
22292 true, the delivery is deferred (&"mailbox has the wrong mode"&); otherwise Exim
22293 continues with the delivery attempt, using the existing mode of the file.
22296 .option notify_comsat appendfile boolean false
22297 If this option is true, the &'comsat'& daemon is notified after every
22298 successful delivery to a user mailbox. This is the daemon that notifies logged
22299 on users about incoming mail.
22302 .option quota appendfile string&!! unset
22303 .cindex "quota" "imposed by Exim"
22304 This option imposes a limit on the size of the file to which Exim is appending,
22305 or to the total space used in the directory tree when the &%directory%& option
22306 is set. In the latter case, computation of the space used is expensive, because
22307 all the files in the directory (and any sub-directories) have to be
22308 individually inspected and their sizes summed. (See &%quota_size_regex%& and
22309 &%maildir_use_size_file%& for ways to avoid this in environments where users
22310 have no shell access to their mailboxes).
22312 As there is no interlock against two simultaneous deliveries into a
22313 multi-file mailbox, it is possible for the quota to be overrun in this case.
22314 For single-file mailboxes, of course, an interlock is a necessity.
22316 A file's size is taken as its &'used'& value. Because of blocking effects, this
22317 may be a lot less than the actual amount of disk space allocated to the file.
22318 If the sizes of a number of files are being added up, the rounding effect can
22319 become quite noticeable, especially on systems that have large block sizes.
22320 Nevertheless, it seems best to stick to the &'used'& figure, because this is
22321 the obvious value which users understand most easily.
22323 The value of the option is expanded, and must then be a numerical value
22324 (decimal point allowed), optionally followed by one of the letters K, M, or G,
22325 for kilobytes, megabytes, or gigabytes, optionally followed by a slash
22326 and further option modifiers. If Exim is running on a system with
22327 large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
22330 The option modifier &%no_check%& can be used to force delivery even if the over
22331 quota condition is met. The quota gets updated as usual.
22333 &*Note*&: A value of zero is interpreted as &"no quota"&.
22335 The expansion happens while Exim is running as root, before it changes uid for
22336 the delivery. This means that files that are inaccessible to the end user can
22337 be used to hold quota values that are looked up in the expansion. When delivery
22338 fails because this quota is exceeded, the handling of the error is as for
22339 system quota failures.
22341 By default, Exim's quota checking mimics system quotas, and restricts the
22342 mailbox to the specified maximum size, though the value is not accurate to the
22343 last byte, owing to separator lines and additional headers that may get added
22344 during message delivery. When a mailbox is nearly full, large messages may get
22345 refused even though small ones are accepted, because the size of the current
22346 message is added to the quota when the check is made. This behaviour can be
22347 changed by setting &%quota_is_inclusive%& false. When this is done, the check
22348 for exceeding the quota does not include the current message. Thus, deliveries
22349 continue until the quota has been exceeded; thereafter, no further messages are
22350 delivered. See also &%quota_warn_threshold%&.
22353 .option quota_directory appendfile string&!! unset
22354 This option defines the directory to check for quota purposes when delivering
22355 into individual files. The default is the delivery directory, or, if a file
22356 called &_maildirfolder_& exists in a maildir directory, the parent of the
22357 delivery directory.
22360 .option quota_filecount appendfile string&!! 0
22361 This option applies when the &%directory%& option is set. It limits the total
22362 number of files in the directory (compare the inode limit in system quotas). It
22363 can only be used if &%quota%& is also set. The value is expanded; an expansion
22364 failure causes delivery to be deferred. A value of zero is interpreted as
22367 The option modifier &%no_check%& can be used to force delivery even if the over
22368 quota condition is met. The quota gets updated as usual.
22370 .option quota_is_inclusive appendfile boolean true
22371 See &%quota%& above.
22374 .option quota_size_regex appendfile string unset
22375 This option applies when one of the delivery modes that writes a separate file
22376 for each message is being used. When Exim wants to find the size of one of
22377 these files in order to test the quota, it first checks &%quota_size_regex%&.
22378 If this is set to a regular expression that matches the file name, and it
22379 captures one string, that string is interpreted as a representation of the
22380 file's size. The value of &%quota_size_regex%& is not expanded.
22382 This feature is useful only when users have no shell access to their mailboxes
22383 &-- otherwise they could defeat the quota simply by renaming the files. This
22384 facility can be used with maildir deliveries, by setting &%maildir_tag%& to add
22385 the file length to the file name. For example:
22387 maildir_tag = ,S=$message_size
22388 quota_size_regex = ,S=(\d+)
22390 An alternative to &$message_size$& is &$message_linecount$&, which contains the
22391 number of lines in the message.
22393 The regular expression should not assume that the length is at the end of the
22394 file name (even though &%maildir_tag%& puts it there) because maildir MUAs
22395 sometimes add other information onto the ends of message file names.
22397 Section &<<SECID136>>& contains further information.
22400 .option quota_warn_message appendfile string&!! "see below"
22401 See below for the use of this option. If it is not set when
22402 &%quota_warn_threshold%& is set, it defaults to
22404 quota_warn_message = "\
22405 To: $local_part@$domain\n\
22406 Subject: Your mailbox\n\n\
22407 This message is automatically created \
22408 by mail delivery software.\n\n\
22409 The size of your mailbox has exceeded \
22410 a warning threshold that is\n\
22411 set by the system administrator.\n"
22415 .option quota_warn_threshold appendfile string&!! 0
22416 .cindex "quota" "warning threshold"
22417 .cindex "mailbox" "size warning"
22418 .cindex "size" "of mailbox"
22419 This option is expanded in the same way as &%quota%& (see above). If the
22420 resulting value is greater than zero, and delivery of the message causes the
22421 size of the file or total space in the directory tree to cross the given
22422 threshold, a warning message is sent. If &%quota%& is also set, the threshold
22423 may be specified as a percentage of it by following the value with a percent
22427 quota_warn_threshold = 75%
22429 If &%quota%& is not set, a setting of &%quota_warn_threshold%& that ends with a
22430 percent sign is ignored.
22432 The warning message itself is specified by the &%quota_warn_message%& option,
22433 and it must start with a &'To:'& header line containing the recipient(s) of the
22434 warning message. These do not necessarily have to include the recipient(s) of
22435 the original message. A &'Subject:'& line should also normally be supplied. You
22436 can include any other header lines that you want. If you do not include a
22437 &'From:'& line, the default is:
22439 From: Mail Delivery System <mailer-daemon@$qualify_domain_sender>
22441 .oindex &%errors_reply_to%&
22442 If you supply a &'Reply-To:'& line, it overrides the global &%errors_reply_to%&
22445 The &%quota%& option does not have to be set in order to use this option; they
22446 are independent of one another except when the threshold is specified as a
22450 .option use_bsmtp appendfile boolean false
22451 .cindex "envelope sender"
22452 If this option is set true, &(appendfile)& writes messages in &"batch SMTP"&
22453 format, with the envelope sender and recipient(s) included as SMTP commands. If
22454 you want to include a leading HELO command with such messages, you can do
22455 so by setting the &%message_prefix%& option. See section &<<SECTbatchSMTP>>&
22456 for details of batch SMTP.
22459 .option use_crlf appendfile boolean false
22460 .cindex "carriage return"
22462 This option causes lines to be terminated with the two-character CRLF sequence
22463 (carriage return, linefeed) instead of just a linefeed character. In the case
22464 of batched SMTP, the byte sequence written to the file is then an exact image
22465 of what would be sent down a real SMTP connection.
22467 &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options
22468 (which are used to supply the traditional &"From&~"& and blank line separators
22469 in Berkeley-style mailboxes) are written verbatim, so must contain their own
22470 carriage return characters if these are needed. In cases where these options
22471 have non-empty defaults, the values end with a single linefeed, so they must be
22472 changed to end with &`\r\n`& if &%use_crlf%& is set.
22475 .option use_fcntl_lock appendfile boolean "see below"
22476 This option controls the use of the &[fcntl()]& function to lock a file for
22477 exclusive use when a message is being appended. It is set by default unless
22478 &%use_flock_lock%& is set. Otherwise, it should be turned off only if you know
22479 that all your MUAs use lock file locking. When both &%use_fcntl_lock%& and
22480 &%use_flock_lock%& are unset, &%use_lockfile%& must be set.
22483 .option use_flock_lock appendfile boolean false
22484 This option is provided to support the use of &[flock()]& for file locking, for
22485 the few situations where it is needed. Most modern operating systems support
22486 &[fcntl()]& and &[lockf()]& locking, and these two functions interwork with
22487 each other. Exim uses &[fcntl()]& locking by default.
22489 This option is required only if you are using an operating system where
22490 &[flock()]& is used by programs that access mailboxes (typically MUAs), and
22491 where &[flock()]& does not correctly interwork with &[fcntl()]&. You can use
22492 both &[fcntl()]& and &[flock()]& locking simultaneously if you want.
22494 .cindex "Solaris" "&[flock()]& support"
22495 Not all operating systems provide &[flock()]&. Some versions of Solaris do not
22496 have it (and some, I think, provide a not quite right version built on top of
22497 &[lockf()]&). If the OS does not have &[flock()]&, Exim will be built without
22498 the ability to use it, and any attempt to do so will cause a configuration
22501 &*Warning*&: &[flock()]& locks do not work on NFS files (unless &[flock()]&
22502 is just being mapped onto &[fcntl()]& by the OS).
22505 .option use_lockfile appendfile boolean "see below"
22506 If this option is turned off, Exim does not attempt to create a lock file when
22507 appending to a mailbox file. In this situation, the only locking is by
22508 &[fcntl()]&. You should only turn &%use_lockfile%& off if you are absolutely
22509 sure that every MUA that is ever going to look at your users' mailboxes uses
22510 &[fcntl()]& rather than a lock file, and even then only when you are not
22511 delivering over NFS from more than one host.
22513 .cindex "NFS" "lock file"
22514 In order to append to an NFS file safely from more than one host, it is
22515 necessary to take out a lock &'before'& opening the file, and the lock file
22516 achieves this. Otherwise, even with &[fcntl()]& locking, there is a risk of
22519 The &%use_lockfile%& option is set by default unless &%use_mbx_lock%& is set.
22520 It is not possible to turn both &%use_lockfile%& and &%use_fcntl_lock%& off,
22521 except when &%mbx_format%& is set.
22524 .option use_mbx_lock appendfile boolean "see below"
22525 This option is available only if Exim has been compiled with SUPPORT_MBX
22526 set in &_Local/Makefile_&. Setting the option specifies that special MBX
22527 locking rules be used. It is set by default if &%mbx_format%& is set and none
22528 of the locking options are mentioned in the configuration. The locking rules
22529 are the same as are used by the &'c-client'& library that underlies Pine and
22530 the IMAP4 and POP daemons that come with it (see the discussion below). The
22531 rules allow for shared access to the mailbox. However, this kind of locking
22532 does not work when the mailbox is NFS mounted.
22534 You can set &%use_mbx_lock%& with either (or both) of &%use_fcntl_lock%& and
22535 &%use_flock_lock%& to control what kind of locking is used in implementing the
22536 MBX locking rules. The default is to use &[fcntl()]& if &%use_mbx_lock%& is set
22537 without &%use_fcntl_lock%& or &%use_flock_lock%&.
22542 .section "Operational details for appending" "SECTopappend"
22543 .cindex "appending to a file"
22544 .cindex "file" "appending"
22545 Before appending to a file, the following preparations are made:
22548 If the name of the file is &_/dev/null_&, no action is taken, and a success
22552 .cindex "directory creation"
22553 If any directories on the file's path are missing, Exim creates them if the
22554 &%create_directory%& option is set. A created directory's mode is given by the
22555 &%directory_mode%& option.
22558 If &%file_format%& is set, the format of an existing file is checked. If this
22559 indicates that a different transport should be used, control is passed to that
22563 .cindex "file" "locking"
22564 .cindex "locking files"
22565 .cindex "NFS" "lock file"
22566 If &%use_lockfile%& is set, a lock file is built in a way that will work
22567 reliably over NFS, as follows:
22570 Create a &"hitching post"& file whose name is that of the lock file with the
22571 current time, primary host name, and process id added, by opening for writing
22572 as a new file. If this fails with an access error, delivery is deferred.
22574 Close the hitching post file, and hard link it to the lock file name.
22576 If the call to &[link()]& succeeds, creation of the lock file has succeeded.
22577 Unlink the hitching post name.
22579 Otherwise, use &[stat()]& to get information about the hitching post file, and
22580 then unlink hitching post name. If the number of links is exactly two, creation
22581 of the lock file succeeded but something (for example, an NFS server crash and
22582 restart) caused this fact not to be communicated to the &[link()]& call.
22584 If creation of the lock file failed, wait for &%lock_interval%& and try again,
22585 up to &%lock_retries%& times. However, since any program that writes to a
22586 mailbox should complete its task very quickly, it is reasonable to time out old
22587 lock files that are normally the result of user agent and system crashes. If an
22588 existing lock file is older than &%lockfile_timeout%& Exim attempts to unlink
22589 it before trying again.
22593 A call is made to &[lstat()]& to discover whether the main file exists, and if
22594 so, what its characteristics are. If &[lstat()]& fails for any reason other
22595 than non-existence, delivery is deferred.
22598 .cindex "symbolic link" "to mailbox"
22599 .cindex "mailbox" "symbolic link"
22600 If the file does exist and is a symbolic link, delivery is deferred, unless the
22601 &%allow_symlink%& option is set, in which case the ownership of the link is
22602 checked, and then &[stat()]& is called to find out about the real file, which
22603 is then subjected to the checks below. The check on the top-level link
22604 ownership prevents one user creating a link for another's mailbox in a sticky
22605 directory, though allowing symbolic links in this case is definitely not a good
22606 idea. If there is a chain of symbolic links, the intermediate ones are not
22610 If the file already exists but is not a regular file, or if the file's owner
22611 and group (if the group is being checked &-- see &%check_group%& above) are
22612 different from the user and group under which the delivery is running,
22613 delivery is deferred.
22616 If the file's permissions are more generous than specified, they are reduced.
22617 If they are insufficient, delivery is deferred, unless &%mode_fail_narrower%&
22618 is set false, in which case the delivery is tried using the existing
22622 The file's inode number is saved, and the file is then opened for appending.
22623 If this fails because the file has vanished, &(appendfile)& behaves as if it
22624 hadn't existed (see below). For any other failures, delivery is deferred.
22627 If the file is opened successfully, check that the inode number hasn't
22628 changed, that it is still a regular file, and that the owner and permissions
22629 have not changed. If anything is wrong, defer delivery and freeze the message.
22632 If the file did not exist originally, defer delivery if the &%file_must_exist%&
22633 option is set. Otherwise, check that the file is being created in a permitted
22634 directory if the &%create_file%& option is set (deferring on failure), and then
22635 open for writing as a new file, with the O_EXCL and O_CREAT options,
22636 except when dealing with a symbolic link (the &%allow_symlink%& option must be
22637 set). In this case, which can happen if the link points to a non-existent file,
22638 the file is opened for writing using O_CREAT but not O_EXCL, because
22639 that prevents link following.
22642 .cindex "loop" "while file testing"
22643 If opening fails because the file exists, obey the tests given above for
22644 existing files. However, to avoid looping in a situation where the file is
22645 being continuously created and destroyed, the exists/not-exists loop is broken
22646 after 10 repetitions, and the message is then frozen.
22649 If opening fails with any other error, defer delivery.
22652 .cindex "file" "locking"
22653 .cindex "locking files"
22654 Once the file is open, unless both &%use_fcntl_lock%& and &%use_flock_lock%&
22655 are false, it is locked using &[fcntl()]& or &[flock()]& or both. If
22656 &%use_mbx_lock%& is false, an exclusive lock is requested in each case.
22657 However, if &%use_mbx_lock%& is true, Exim takes out a shared lock on the open
22658 file, and an exclusive lock on the file whose name is
22660 /tmp/.<device-number>.<inode-number>
22662 using the device and inode numbers of the open mailbox file, in accordance with
22663 the MBX locking rules. This file is created with a mode that is specified by
22664 the &%lockfile_mode%& option.
22666 If Exim fails to lock the file, there are two possible courses of action,
22667 depending on the value of the locking timeout. This is obtained from
22668 &%lock_fcntl_timeout%& or &%lock_flock_timeout%&, as appropriate.
22670 If the timeout value is zero, the file is closed, Exim waits for
22671 &%lock_interval%&, and then goes back and re-opens the file as above and tries
22672 to lock it again. This happens up to &%lock_retries%& times, after which the
22673 delivery is deferred.
22675 If the timeout has a value greater than zero, blocking calls to &[fcntl()]& or
22676 &[flock()]& are used (with the given timeout), so there has already been some
22677 waiting involved by the time locking fails. Nevertheless, Exim does not give up
22678 immediately. It retries up to
22680 (lock_retries * lock_interval) / <timeout>
22682 times (rounded up).
22685 At the end of delivery, Exim closes the file (which releases the &[fcntl()]&
22686 and/or &[flock()]& locks) and then deletes the lock file if one was created.
22689 .section "Operational details for delivery to a new file" "SECTopdir"
22690 .cindex "delivery" "to single file"
22691 .cindex "&""From""& line"
22692 When the &%directory%& option is set instead of &%file%&, each message is
22693 delivered into a newly-created file or set of files. When &(appendfile)& is
22694 activated directly from a &(redirect)& router, neither &%file%& nor
22695 &%directory%& is normally set, because the path for delivery is supplied by the
22696 router. (See for example, the &(address_file)& transport in the default
22697 configuration.) In this case, delivery is to a new file if either the path name
22698 ends in &`/`&, or the &%maildir_format%& or &%mailstore_format%& option is set.
22700 No locking is required while writing the message to a new file, so the various
22701 locking options of the transport are ignored. The &"From"& line that by default
22702 separates messages in a single file is not normally needed, nor is the escaping
22703 of message lines that start with &"From"&, and there is no need to ensure a
22704 newline at the end of each message. Consequently, the default values for
22705 &%check_string%&, &%message_prefix%&, and &%message_suffix%& are all unset when
22706 any of &%directory%&, &%maildir_format%&, or &%mailstore_format%& is set.
22708 If Exim is required to check a &%quota%& setting, it adds up the sizes of all
22709 the files in the delivery directory by default. However, you can specify a
22710 different directory by setting &%quota_directory%&. Also, for maildir
22711 deliveries (see below) the &_maildirfolder_& convention is honoured.
22714 .cindex "maildir format"
22715 .cindex "mailstore format"
22716 There are three different ways in which delivery to individual files can be
22717 done, controlled by the settings of the &%maildir_format%& and
22718 &%mailstore_format%& options. Note that code to support maildir or mailstore
22719 formats is not included in the binary unless SUPPORT_MAILDIR or
22720 SUPPORT_MAILSTORE, respectively, is set in &_Local/Makefile_&.
22722 .cindex "directory creation"
22723 In all three cases an attempt is made to create the directory and any necessary
22724 sub-directories if they do not exist, provided that the &%create_directory%&
22725 option is set (the default). The location of a created directory can be
22726 constrained by setting &%create_file%&. A created directory's mode is given by
22727 the &%directory_mode%& option. If creation fails, or if the
22728 &%create_directory%& option is not set when creation is required, delivery is
22733 .section "Maildir delivery" "SECTmaildirdelivery"
22734 .cindex "maildir format" "description of"
22735 If the &%maildir_format%& option is true, Exim delivers each message by writing
22736 it to a file whose name is &_tmp/<stime>.H<mtime>P<pid>.<host>_& in the
22737 directory that is defined by the &%directory%& option (the &"delivery
22738 directory"&). If the delivery is successful, the file is renamed into the
22739 &_new_& subdirectory.
22741 In the file name, <&'stime'&> is the current time of day in seconds, and
22742 <&'mtime'&> is the microsecond fraction of the time. After a maildir delivery,
22743 Exim checks that the time-of-day clock has moved on by at least one microsecond
22744 before terminating the delivery process. This guarantees uniqueness for the
22745 file name. However, as a precaution, Exim calls &[stat()]& for the file before
22746 opening it. If any response other than ENOENT (does not exist) is given,
22747 Exim waits 2 seconds and tries again, up to &%maildir_retries%& times.
22749 Before Exim carries out a maildir delivery, it ensures that subdirectories
22750 called &_new_&, &_cur_&, and &_tmp_& exist in the delivery directory. If they
22751 do not exist, Exim tries to create them and any superior directories in their
22752 path, subject to the &%create_directory%& and &%create_file%& options. If the
22753 &%maildirfolder_create_regex%& option is set, and the regular expression it
22754 contains matches the delivery directory, Exim also ensures that a file called
22755 &_maildirfolder_& exists in the delivery directory. If a missing directory or
22756 &_maildirfolder_& file cannot be created, delivery is deferred.
22758 These features make it possible to use Exim to create all the necessary files
22759 and directories in a maildir mailbox, including subdirectories for maildir++
22760 folders. Consider this example:
22762 maildir_format = true
22763 directory = /var/mail/$local_part\
22764 ${if eq{$local_part_suffix}{}{}\
22765 {/.${substr_1:$local_part_suffix}}}
22766 maildirfolder_create_regex = /\.[^/]+$
22768 If &$local_part_suffix$& is empty (there was no suffix for the local part),
22769 delivery is into a toplevel maildir with a name like &_/var/mail/pimbo_& (for
22770 the user called &'pimbo'&). The pattern in &%maildirfolder_create_regex%& does
22771 not match this name, so Exim will not look for or create the file
22772 &_/var/mail/pimbo/maildirfolder_&, though it will create
22773 &_/var/mail/pimbo/{cur,new,tmp}_& if necessary.
22775 However, if &$local_part_suffix$& contains &`-eximusers`& (for example),
22776 delivery is into the maildir++ folder &_/var/mail/pimbo/.eximusers_&, which
22777 does match &%maildirfolder_create_regex%&. In this case, Exim will create
22778 &_/var/mail/pimbo/.eximusers/maildirfolder_& as well as the three maildir
22779 directories &_/var/mail/pimbo/.eximusers/{cur,new,tmp}_&.
22781 &*Warning:*& Take care when setting &%maildirfolder_create_regex%& that it does
22782 not inadvertently match the toplevel maildir directory, because a
22783 &_maildirfolder_& file at top level would completely break quota calculations.
22785 .cindex "quota" "in maildir delivery"
22786 .cindex "maildir++"
22787 If Exim is required to check a &%quota%& setting before a maildir delivery, and
22788 &%quota_directory%& is not set, it looks for a file called &_maildirfolder_& in
22789 the maildir directory (alongside &_new_&, &_cur_&, &_tmp_&). If this exists,
22790 Exim assumes the directory is a maildir++ folder directory, which is one level
22791 down from the user's top level mailbox directory. This causes it to start at
22792 the parent directory instead of the current directory when calculating the
22793 amount of space used.
22795 One problem with delivering into a multi-file mailbox is that it is
22796 computationally expensive to compute the size of the mailbox for quota
22797 checking. Various approaches have been taken to reduce the amount of work
22798 needed. The next two sections describe two of them. A third alternative is to
22799 use some external process for maintaining the size data, and use the expansion
22800 of the &%mailbox_size%& option as a way of importing it into Exim.
22805 .section "Using tags to record message sizes" "SECID135"
22806 If &%maildir_tag%& is set, the string is expanded for each delivery.
22807 When the maildir file is renamed into the &_new_& sub-directory, the
22808 tag is added to its name. However, if adding the tag takes the length of the
22809 name to the point where the test &[stat()]& call fails with ENAMETOOLONG,
22810 the tag is dropped and the maildir file is created with no tag.
22813 .vindex "&$message_size$&"
22814 Tags can be used to encode the size of files in their names; see
22815 &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%&
22816 happens after the message has been written. The value of the &$message_size$&
22817 variable is set to the number of bytes actually written. If the expansion is
22818 forced to fail, the tag is ignored, but a non-forced failure causes delivery to
22819 be deferred. The expanded tag may contain any printing characters except &"/"&.
22820 Non-printing characters in the string are ignored; if the resulting string is
22821 empty, it is ignored. If it starts with an alphanumeric character, a leading
22822 colon is inserted; this default has not proven to be the path that popular
22823 maildir implementations have chosen (but changing it in Exim would break
22824 backwards compatibility).
22826 For one common implementation, you might set:
22828 maildir_tag = ,S=${message_size}
22830 but you should check the documentation of the other software to be sure.
22832 It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%&
22833 as this allows Exim to extract the size from your tag, instead of having to
22834 &[stat()]& each message file.
22837 .section "Using a maildirsize file" "SECID136"
22838 .cindex "quota" "in maildir delivery"
22839 .cindex "maildir format" "&_maildirsize_& file"
22840 If &%maildir_use_size_file%& is true, Exim implements the maildir++ rules for
22841 storing quota and message size information in a file called &_maildirsize_&
22842 within the toplevel maildir directory. If this file does not exist, Exim
22843 creates it, setting the quota from the &%quota%& option of the transport. If
22844 the maildir directory itself does not exist, it is created before any attempt
22845 to write a &_maildirsize_& file.
22847 The &_maildirsize_& file is used to hold information about the sizes of
22848 messages in the maildir, thus speeding up quota calculations. The quota value
22849 in the file is just a cache; if the quota is changed in the transport, the new
22850 value overrides the cached value when the next message is delivered. The cache
22851 is maintained for the benefit of other programs that access the maildir and
22852 need to know the quota.
22854 If the &%quota%& option in the transport is unset or zero, the &_maildirsize_&
22855 file is maintained (with a zero quota setting), but no quota is imposed.
22857 A regular expression is available for controlling which directories in the
22858 maildir participate in quota calculations when a &_maildirsizefile_& is in use.
22859 See the description of the &%maildir_quota_directory_regex%& option above for
22863 .section "Mailstore delivery" "SECID137"
22864 .cindex "mailstore format" "description of"
22865 If the &%mailstore_format%& option is true, each message is written as two
22866 files in the given directory. A unique base name is constructed from the
22867 message id and the current delivery process, and the files that are written use
22868 this base name plus the suffixes &_.env_& and &_.msg_&. The &_.env_& file
22869 contains the message's envelope, and the &_.msg_& file contains the message
22870 itself. The base name is placed in the variable &$mailstore_basename$&.
22872 During delivery, the envelope is first written to a file with the suffix
22873 &_.tmp_&. The &_.msg_& file is then written, and when it is complete, the
22874 &_.tmp_& file is renamed as the &_.env_& file. Programs that access messages in
22875 mailstore format should wait for the presence of both a &_.msg_& and a &_.env_&
22876 file before accessing either of them. An alternative approach is to wait for
22877 the absence of a &_.tmp_& file.
22879 The envelope file starts with any text defined by the &%mailstore_prefix%&
22880 option, expanded and terminated by a newline if there isn't one. Then follows
22881 the sender address on one line, then all the recipient addresses, one per line.
22882 There can be more than one recipient only if the &%batch_max%& option is set
22883 greater than one. Finally, &%mailstore_suffix%& is expanded and the result
22884 appended to the file, followed by a newline if it does not end with one.
22886 If expansion of &%mailstore_prefix%& or &%mailstore_suffix%& ends with a forced
22887 failure, it is ignored. Other expansion errors are treated as serious
22888 configuration errors, and delivery is deferred. The variable
22889 &$mailstore_basename$& is available for use during these expansions.
22892 .section "Non-special new file delivery" "SECID138"
22893 If neither &%maildir_format%& nor &%mailstore_format%& is set, a single new
22894 file is created directly in the named directory. For example, when delivering
22895 messages into files in batched SMTP format for later delivery to some host (see
22896 section &<<SECTbatchSMTP>>&), a setting such as
22898 directory = /var/bsmtp/$host
22900 might be used. A message is written to a file with a temporary name, which is
22901 then renamed when the delivery is complete. The final name is obtained by
22902 expanding the contents of the &%directory_file%& option.
22903 .ecindex IIDapptra1
22904 .ecindex IIDapptra2
22911 . ////////////////////////////////////////////////////////////////////////////
22912 . ////////////////////////////////////////////////////////////////////////////
22914 .chapter "The autoreply transport" "CHID8"
22915 .scindex IIDauttra1 "transports" "&(autoreply)&"
22916 .scindex IIDauttra2 "&(autoreply)& transport"
22917 The &(autoreply)& transport is not a true transport in that it does not cause
22918 the message to be transmitted. Instead, it generates a new mail message as an
22919 automatic reply to the incoming message. &'References:'& and
22920 &'Auto-Submitted:'& header lines are included. These are constructed according
22921 to the rules in RFCs 2822 and 3834, respectively.
22923 If the router that passes the message to this transport does not have the
22924 &%unseen%& option set, the original message (for the current recipient) is not
22925 delivered anywhere. However, when the &%unseen%& option is set on the router
22926 that passes the message to this transport, routing of the address continues, so
22927 another router can set up a normal message delivery.
22930 The &(autoreply)& transport is usually run as the result of mail filtering, a
22931 &"vacation"& message being the standard example. However, it can also be run
22932 directly from a router like any other transport. To reduce the possibility of
22933 message cascades, messages created by the &(autoreply)& transport always have
22934 empty envelope sender addresses, like bounce messages.
22936 The parameters of the message to be sent can be specified in the configuration
22937 by options described below. However, these are used only when the address
22938 passed to the transport does not contain its own reply information. When the
22939 transport is run as a consequence of a
22941 or &%vacation%& command in a filter file, the parameters of the message are
22942 supplied by the filter, and passed with the address. The transport's options
22943 that define the message are then ignored (so they are not usually set in this
22944 case). The message is specified entirely by the filter or by the transport; it
22945 is never built from a mixture of options. However, the &%file_optional%&,
22946 &%mode%&, and &%return_message%& options apply in all cases.
22948 &(Autoreply)& is implemented as a local transport. When used as a result of a
22949 command in a user's filter file, &(autoreply)& normally runs under the uid and
22950 gid of the user, and with appropriate current and home directories (see chapter
22951 &<<CHAPenvironment>>&).
22953 There is a subtle difference between routing a message to a &(pipe)& transport
22954 that generates some text to be returned to the sender, and routing it to an
22955 &(autoreply)& transport. This difference is noticeable only if more than one
22956 address from the same message is so handled. In the case of a pipe, the
22957 separate outputs from the different addresses are gathered up and returned to
22958 the sender in a single message, whereas if &(autoreply)& is used, a separate
22959 message is generated for each address that is passed to it.
22961 Non-printing characters are not permitted in the header lines generated for the
22962 message that &(autoreply)& creates, with the exception of newlines that are
22963 immediately followed by white space. If any non-printing characters are found,
22964 the transport defers.
22965 Whether characters with the top bit set count as printing characters or not is
22966 controlled by the &%print_topbitchars%& global option.
22968 If any of the generic options for manipulating headers (for example,
22969 &%headers_add%&) are set on an &(autoreply)& transport, they apply to the copy
22970 of the original message that is included in the generated message when
22971 &%return_message%& is set. They do not apply to the generated message itself.
22973 .vindex "&$sender_address$&"
22974 If the &(autoreply)& transport receives return code 2 from Exim when it submits
22975 the message, indicating that there were no recipients, it does not treat this
22976 as an error. This means that autoreplies sent to &$sender_address$& when this
22977 is empty (because the incoming message is a bounce message) do not cause
22978 problems. They are just discarded.
22982 .section "Private options for autoreply" "SECID139"
22983 .cindex "options" "&(autoreply)& transport"
22985 .option bcc autoreply string&!! unset
22986 This specifies the addresses that are to receive &"blind carbon copies"& of the
22987 message when the message is specified by the transport.
22990 .option cc autoreply string&!! unset
22991 This specifies recipients of the message and the contents of the &'Cc:'& header
22992 when the message is specified by the transport.
22995 .option file autoreply string&!! unset
22996 The contents of the file are sent as the body of the message when the message
22997 is specified by the transport. If both &%file%& and &%text%& are set, the text
22998 string comes first.
23001 .option file_expand autoreply boolean false
23002 If this is set, the contents of the file named by the &%file%& option are
23003 subjected to string expansion as they are added to the message.
23006 .option file_optional autoreply boolean false
23007 If this option is true, no error is generated if the file named by the &%file%&
23008 option or passed with the address does not exist or cannot be read.
23011 .option from autoreply string&!! unset
23012 This specifies the contents of the &'From:'& header when the message is
23013 specified by the transport.
23016 .option headers autoreply string&!! unset
23017 This specifies additional RFC 2822 headers that are to be added to the message
23018 when the message is specified by the transport. Several can be given by using
23019 &"\n"& to separate them. There is no check on the format.
23022 .option log autoreply string&!! unset
23023 This option names a file in which a record of every message sent is logged when
23024 the message is specified by the transport.
23027 .option mode autoreply "octal integer" 0600
23028 If either the log file or the &"once"& file has to be created, this mode is
23032 .option never_mail autoreply "address list&!!" unset
23033 If any run of the transport creates a message with a recipient that matches any
23034 item in the list, that recipient is quietly discarded. If all recipients are
23035 discarded, no message is created. This applies both when the recipients are
23036 generated by a filter and when they are specified in the transport.
23040 .option once autoreply string&!! unset
23041 This option names a file or DBM database in which a record of each &'To:'&
23042 recipient is kept when the message is specified by the transport. &*Note*&:
23043 This does not apply to &'Cc:'& or &'Bcc:'& recipients.
23045 If &%once%& is unset, or is set to an empty string, the message is always sent.
23046 By default, if &%once%& is set to a non-empty file name, the message
23047 is not sent if a potential recipient is already listed in the database.
23048 However, if the &%once_repeat%& option specifies a time greater than zero, the
23049 message is sent if that much time has elapsed since a message was last sent to
23050 this recipient. A setting of zero time for &%once_repeat%& (the default)
23051 prevents a message from being sent a second time &-- in this case, zero means
23054 If &%once_file_size%& is zero, a DBM database is used to remember recipients,
23055 and it is allowed to grow as large as necessary. If &%once_file_size%& is set
23056 greater than zero, it changes the way Exim implements the &%once%& option.
23057 Instead of using a DBM file to record every recipient it sends to, it uses a
23058 regular file, whose size will never get larger than the given value.
23060 In the file, Exim keeps a linear list of recipient addresses and the times at
23061 which they were sent messages. If the file is full when a new address needs to
23062 be added, the oldest address is dropped. If &%once_repeat%& is not set, this
23063 means that a given recipient may receive multiple messages, but at
23064 unpredictable intervals that depend on the rate of turnover of addresses in the
23065 file. If &%once_repeat%& is set, it specifies a maximum time between repeats.
23068 .option once_file_size autoreply integer 0
23069 See &%once%& above.
23072 .option once_repeat autoreply time&!! 0s
23073 See &%once%& above.
23074 After expansion, the value of this option must be a valid time value.
23077 .option reply_to autoreply string&!! unset
23078 This specifies the contents of the &'Reply-To:'& header when the message is
23079 specified by the transport.
23082 .option return_message autoreply boolean false
23083 If this is set, a copy of the original message is returned with the new
23084 message, subject to the maximum size set in the &%return_size_limit%& global
23085 configuration option.
23088 .option subject autoreply string&!! unset
23089 This specifies the contents of the &'Subject:'& header when the message is
23090 specified by the transport. It is tempting to quote the original subject in
23091 automatic responses. For example:
23093 subject = Re: $h_subject:
23095 There is a danger in doing this, however. It may allow a third party to
23096 subscribe your users to an opt-in mailing list, provided that the list accepts
23097 bounce messages as subscription confirmations. Well-managed lists require a
23098 non-bounce message to confirm a subscription, so the danger is relatively
23103 .option text autoreply string&!! unset
23104 This specifies a single string to be used as the body of the message when the
23105 message is specified by the transport. If both &%text%& and &%file%& are set,
23106 the text comes first.
23109 .option to autoreply string&!! unset
23110 This specifies recipients of the message and the contents of the &'To:'& header
23111 when the message is specified by the transport.
23112 .ecindex IIDauttra1
23113 .ecindex IIDauttra2
23118 . ////////////////////////////////////////////////////////////////////////////
23119 . ////////////////////////////////////////////////////////////////////////////
23121 .chapter "The lmtp transport" "CHAPLMTP"
23122 .cindex "transports" "&(lmtp)&"
23123 .cindex "&(lmtp)& transport"
23124 .cindex "LMTP" "over a pipe"
23125 .cindex "LMTP" "over a socket"
23126 The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a
23128 or by interacting with a Unix domain socket.
23129 This transport is something of a cross between the &(pipe)& and &(smtp)&
23130 transports. Exim also has support for using LMTP over TCP/IP; this is
23131 implemented as an option for the &(smtp)& transport. Because LMTP is expected
23132 to be of minority interest, the default build-time configure in &_src/EDITME_&
23133 has it commented out. You need to ensure that
23137 .cindex "options" "&(lmtp)& transport"
23138 is present in your &_Local/Makefile_& in order to have the &(lmtp)& transport
23139 included in the Exim binary. The private options of the &(lmtp)& transport are
23142 .option batch_id lmtp string&!! unset
23143 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23146 .option batch_max lmtp integer 1
23147 This limits the number of addresses that can be handled in a single delivery.
23148 Most LMTP servers can handle several addresses at once, so it is normally a
23149 good idea to increase this value. See the description of local delivery
23150 batching in chapter &<<CHAPbatching>>&.
23153 .option command lmtp string&!! unset
23154 This option must be set if &%socket%& is not set. The string is a command which
23155 is run in a separate process. It is split up into a command name and list of
23156 arguments, each of which is separately expanded (so expansion cannot change the
23157 number of arguments). The command is run directly, not via a shell. The message
23158 is passed to the new process using the standard input and output to operate the
23161 .option ignore_quota lmtp boolean false
23162 .cindex "LMTP" "ignoring quota errors"
23163 If this option is set true, the string &`IGNOREQUOTA`& is added to RCPT
23164 commands, provided that the LMTP server has advertised support for IGNOREQUOTA
23165 in its response to the LHLO command.
23167 .option socket lmtp string&!! unset
23168 This option must be set if &%command%& is not set. The result of expansion must
23169 be the name of a Unix domain socket. The transport connects to the socket and
23170 delivers the message to it using the LMTP protocol.
23173 .option timeout lmtp time 5m
23174 The transport is aborted if the created process or Unix domain socket does not
23175 respond to LMTP commands or message input within this timeout. Delivery
23176 is deferred, and will be tried again later. Here is an example of a typical
23181 command = /some/local/lmtp/delivery/program
23185 This delivers up to 20 addresses at a time, in a mixture of domains if
23186 necessary, running as the user &'exim'&.
23190 . ////////////////////////////////////////////////////////////////////////////
23191 . ////////////////////////////////////////////////////////////////////////////
23193 .chapter "The pipe transport" "CHAPpipetransport"
23194 .scindex IIDpiptra1 "transports" "&(pipe)&"
23195 .scindex IIDpiptra2 "&(pipe)& transport"
23196 The &(pipe)& transport is used to deliver messages via a pipe to a command
23197 running in another process. One example is the use of &(pipe)& as a
23198 pseudo-remote transport for passing messages to some other delivery mechanism
23199 (such as UUCP). Another is the use by individual users to automatically process
23200 their incoming messages. The &(pipe)& transport can be used in one of the
23204 .vindex "&$local_part$&"
23205 A router routes one address to a transport in the normal way, and the
23206 transport is configured as a &(pipe)& transport. In this case, &$local_part$&
23207 contains the local part of the address (as usual), and the command that is run
23208 is specified by the &%command%& option on the transport.
23210 .vindex "&$pipe_addresses$&"
23211 If the &%batch_max%& option is set greater than 1 (the default is 1), the
23212 transport can handle more than one address in a single run. In this case, when
23213 more than one address is routed to the transport, &$local_part$& is not set
23214 (because it is not unique). However, the pseudo-variable &$pipe_addresses$&
23215 (described in section &<<SECThowcommandrun>>& below) contains all the addresses
23216 that are routed to the transport.
23218 .vindex "&$address_pipe$&"
23219 A router redirects an address directly to a pipe command (for example, from an
23220 alias or forward file). In this case, &$address_pipe$& contains the text of the
23221 pipe command, and the &%command%& option on the transport is ignored unless
23222 &%force_command%& is set. If only one address is being transported
23223 (&%batch_max%& is not greater than one, or only one address was redirected to
23224 this pipe command), &$local_part$& contains the local part that was redirected.
23228 The &(pipe)& transport is a non-interactive delivery method. Exim can also
23229 deliver messages over pipes using the LMTP interactive protocol. This is
23230 implemented by the &(lmtp)& transport.
23232 In the case when &(pipe)& is run as a consequence of an entry in a local user's
23233 &_.forward_& file, the command runs under the uid and gid of that user. In
23234 other cases, the uid and gid have to be specified explicitly, either on the
23235 transport or on the router that handles the address. Current and &"home"&
23236 directories are also controllable. See chapter &<<CHAPenvironment>>& for
23237 details of the local delivery environment and chapter &<<CHAPbatching>>&
23238 for a discussion of local delivery batching.
23241 .section "Concurrent delivery" "SECID140"
23242 If two messages arrive at almost the same time, and both are routed to a pipe
23243 delivery, the two pipe transports may be run concurrently. You must ensure that
23244 any pipe commands you set up are robust against this happening. If the commands
23245 write to a file, the &%exim_lock%& utility might be of use.
23246 Alternatively the &%max_parallel%& option could be used with a value
23247 of "1" to enforce serialization.
23252 .section "Returned status and data" "SECID141"
23253 .cindex "&(pipe)& transport" "returned data"
23254 If the command exits with a non-zero return code, the delivery is deemed to
23255 have failed, unless either the &%ignore_status%& option is set (in which case
23256 the return code is treated as zero), or the return code is one of those listed
23257 in the &%temp_errors%& option, which are interpreted as meaning &"try again
23258 later"&. In this case, delivery is deferred. Details of a permanent failure are
23259 logged, but are not included in the bounce message, which merely contains
23260 &"local delivery failed"&.
23262 If the command exits on a signal and the &%freeze_signal%& option is set then
23263 the message will be frozen in the queue. If that option is not set, a bounce
23264 will be sent as normal.
23266 If the return code is greater than 128 and the command being run is a shell
23267 script, it normally means that the script was terminated by a signal whose
23268 value is the return code minus 128. The &%freeze_signal%& option does not
23269 apply in this case.
23271 If Exim is unable to run the command (that is, if &[execve()]& fails), the
23272 return code is set to 127. This is the value that a shell returns if it is
23273 asked to run a non-existent command. The wording for the log line suggests that
23274 a non-existent command may be the problem.
23276 The &%return_output%& option can affect the result of a pipe delivery. If it is
23277 set and the command produces any output on its standard output or standard
23278 error streams, the command is considered to have failed, even if it gave a zero
23279 return code or if &%ignore_status%& is set. The output from the command is
23280 included as part of the bounce message. The &%return_fail_output%& option is
23281 similar, except that output is returned only when the command exits with a
23282 failure return code, that is, a value other than zero or a code that matches
23287 .section "How the command is run" "SECThowcommandrun"
23288 .cindex "&(pipe)& transport" "path for command"
23289 The command line is (by default) broken down into a command name and arguments
23290 by the &(pipe)& transport itself. The &%allow_commands%& and
23291 &%restrict_to_path%& options can be used to restrict the commands that may be
23294 .cindex "quoting" "in pipe command"
23295 Unquoted arguments are delimited by white space. If an argument appears in
23296 double quotes, backslash is interpreted as an escape character in the usual
23297 way. If an argument appears in single quotes, no escaping is done.
23299 String expansion is applied to the command line except when it comes from a
23300 traditional &_.forward_& file (commands from a filter file are expanded). The
23301 expansion is applied to each argument in turn rather than to the whole line.
23302 For this reason, any string expansion item that contains white space must be
23303 quoted so as to be contained within a single argument. A setting such as
23305 command = /some/path ${if eq{$local_part}{postmaster}{xx}{yy}}
23307 will not work, because the expansion item gets split between several
23308 arguments. You have to write
23310 command = /some/path "${if eq{$local_part}{postmaster}{xx}{yy}}"
23312 to ensure that it is all in one argument. The expansion is done in this way,
23313 argument by argument, so that the number of arguments cannot be changed as a
23314 result of expansion, and quotes or backslashes in inserted variables do not
23315 interact with external quoting. However, this leads to problems if you want to
23316 generate multiple arguments (or the command name plus arguments) from a single
23317 expansion. In this situation, the simplest solution is to use a shell. For
23320 command = /bin/sh -c ${lookup{$local_part}lsearch{/some/file}}
23323 .cindex "transport" "filter"
23324 .cindex "filter" "transport filter"
23325 .vindex "&$pipe_addresses$&"
23326 Special handling takes place when an argument consists of precisely the text
23327 &`$pipe_addresses`&. This is not a general expansion variable; the only
23328 place this string is recognized is when it appears as an argument for a pipe or
23329 transport filter command. It causes each address that is being handled to be
23330 inserted in the argument list at that point &'as a separate argument'&. This
23331 avoids any problems with spaces or shell metacharacters, and is of use when a
23332 &(pipe)& transport is handling groups of addresses in a batch.
23334 If &%force_command%& is enabled on the transport, Special handling takes place
23335 for an argument that consists of precisely the text &`$address_pipe`&. It
23336 is handled similarly to &$pipe_addresses$& above. It is expanded and each
23337 argument is inserted in the argument list at that point
23338 &'as a separate argument'&. The &`$address_pipe`& item does not need to be
23339 the only item in the argument; in fact, if it were then &%force_command%&
23340 should behave as a no-op. Rather, it should be used to adjust the command
23341 run while preserving the argument vector separation.
23343 After splitting up into arguments and expansion, the resulting command is run
23344 in a subprocess directly from the transport, &'not'& under a shell. The
23345 message that is being delivered is supplied on the standard input, and the
23346 standard output and standard error are both connected to a single pipe that is
23347 read by Exim. The &%max_output%& option controls how much output the command
23348 may produce, and the &%return_output%& and &%return_fail_output%& options
23349 control what is done with it.
23351 Not running the command under a shell (by default) lessens the security risks
23352 in cases when a command from a user's filter file is built out of data that was
23353 taken from an incoming message. If a shell is required, it can of course be
23354 explicitly specified as the command to be run. However, there are circumstances
23355 where existing commands (for example, in &_.forward_& files) expect to be run
23356 under a shell and cannot easily be modified. To allow for these cases, there is
23357 an option called &%use_shell%&, which changes the way the &(pipe)& transport
23358 works. Instead of breaking up the command line as just described, it expands it
23359 as a single string and passes the result to &_/bin/sh_&. The
23360 &%restrict_to_path%& option and the &$pipe_addresses$& facility cannot be used
23361 with &%use_shell%&, and the whole mechanism is inherently less secure.
23365 .section "Environment variables" "SECTpipeenv"
23366 .cindex "&(pipe)& transport" "environment for command"
23367 .cindex "environment" "&(pipe)& transport"
23368 The environment variables listed below are set up when the command is invoked.
23369 This list is a compromise for maximum compatibility with other MTAs. Note that
23370 the &%environment%& option can be used to add additional variables to this
23371 environment. The environment for the &(pipe)& transport is not subject
23372 to the &%add_environment%& and &%keep_environment%& main config options.
23374 &`DOMAIN `& the domain of the address
23375 &`HOME `& the home directory, if set
23376 &`HOST `& the host name when called from a router (see below)
23377 &`LOCAL_PART `& see below
23378 &`LOCAL_PART_PREFIX `& see below
23379 &`LOCAL_PART_SUFFIX `& see below
23380 &`LOGNAME `& see below
23381 &`MESSAGE_ID `& Exim's local ID for the message
23382 &`PATH `& as specified by the &%path%& option below
23383 &`QUALIFY_DOMAIN `& the sender qualification domain
23384 &`RECIPIENT `& the complete recipient address
23385 &`SENDER `& the sender of the message (empty if a bounce)
23386 &`SHELL `& &`/bin/sh`&
23387 &`TZ `& the value of the &%timezone%& option, if set
23388 &`USER `& see below
23390 When a &(pipe)& transport is called directly from (for example) an &(accept)&
23391 router, LOCAL_PART is set to the local part of the address. When it is
23392 called as a result of a forward or alias expansion, LOCAL_PART is set to
23393 the local part of the address that was expanded. In both cases, any affixes are
23394 removed from the local part, and made available in LOCAL_PART_PREFIX and
23395 LOCAL_PART_SUFFIX, respectively. LOGNAME and USER are set to the
23396 same value as LOCAL_PART for compatibility with other MTAs.
23399 HOST is set only when a &(pipe)& transport is called from a router that
23400 associates hosts with an address, typically when using &(pipe)& as a
23401 pseudo-remote transport. HOST is set to the first host name specified by
23405 If the transport's generic &%home_directory%& option is set, its value is used
23406 for the HOME environment variable. Otherwise, a home directory may be set
23407 by the router's &%transport_home_directory%& option, which defaults to the
23408 user's home directory if &%check_local_user%& is set.
23411 .section "Private options for pipe" "SECID142"
23412 .cindex "options" "&(pipe)& transport"
23416 .option allow_commands pipe "string list&!!" unset
23417 .cindex "&(pipe)& transport" "permitted commands"
23418 The string is expanded, and is then interpreted as a colon-separated list of
23419 permitted commands. If &%restrict_to_path%& is not set, the only commands
23420 permitted are those in the &%allow_commands%& list. They need not be absolute
23421 paths; the &%path%& option is still used for relative paths. If
23422 &%restrict_to_path%& is set with &%allow_commands%&, the command must either be
23423 in the &%allow_commands%& list, or a name without any slashes that is found on
23424 the path. In other words, if neither &%allow_commands%& nor
23425 &%restrict_to_path%& is set, there is no restriction on the command, but
23426 otherwise only commands that are permitted by one or the other are allowed. For
23429 allow_commands = /usr/bin/vacation
23431 and &%restrict_to_path%& is not set, the only permitted command is
23432 &_/usr/bin/vacation_&. The &%allow_commands%& option may not be set if
23433 &%use_shell%& is set.
23436 .option batch_id pipe string&!! unset
23437 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23440 .option batch_max pipe integer 1
23441 This limits the number of addresses that can be handled in a single delivery.
23442 See the description of local delivery batching in chapter &<<CHAPbatching>>&.
23445 .option check_string pipe string unset
23446 As &(pipe)& writes the message, the start of each line is tested for matching
23447 &%check_string%&, and if it does, the initial matching characters are replaced
23448 by the contents of &%escape_string%&, provided both are set. The value of
23449 &%check_string%& is a literal string, not a regular expression, and the case of
23450 any letters it contains is significant. When &%use_bsmtp%& is set, the contents
23451 of &%check_string%& and &%escape_string%& are forced to values that implement
23452 the SMTP escaping protocol. Any settings made in the configuration file are
23456 .option command pipe string&!! unset
23457 This option need not be set when &(pipe)& is being used to deliver to pipes
23458 obtained directly from address redirections. In other cases, the option must be
23459 set, to provide a command to be run. It need not yield an absolute path (see
23460 the &%path%& option below). The command is split up into separate arguments by
23461 Exim, and each argument is separately expanded, as described in section
23462 &<<SECThowcommandrun>>& above.
23465 .option environment pipe string&!! unset
23466 .cindex "&(pipe)& transport" "environment for command"
23467 .cindex "environment" "&(pipe)& transport"
23468 This option is used to add additional variables to the environment in which the
23469 command runs (see section &<<SECTpipeenv>>& for the default list). Its value is
23470 a string which is expanded, and then interpreted as a colon-separated list of
23471 environment settings of the form <&'name'&>=<&'value'&>.
23474 .option escape_string pipe string unset
23475 See &%check_string%& above.
23478 .option freeze_exec_fail pipe boolean false
23479 .cindex "exec failure"
23480 .cindex "failure of exec"
23481 .cindex "&(pipe)& transport" "failure of exec"
23482 Failure to exec the command in a pipe transport is by default treated like
23483 any other failure while running the command. However, if &%freeze_exec_fail%&
23484 is set, failure to exec is treated specially, and causes the message to be
23485 frozen, whatever the setting of &%ignore_status%&.
23488 .option freeze_signal pipe boolean false
23489 .cindex "signal exit"
23490 .cindex "&(pipe)& transport", "signal exit"
23491 Normally if the process run by a command in a pipe transport exits on a signal,
23492 a bounce message is sent. If &%freeze_signal%& is set, the message will be
23493 frozen in Exim's queue instead.
23496 .option force_command pipe boolean false
23497 .cindex "force command"
23498 .cindex "&(pipe)& transport", "force command"
23499 Normally when a router redirects an address directly to a pipe command
23500 the &%command%& option on the transport is ignored. If &%force_command%&
23501 is set, the &%command%& option will used. This is especially
23502 useful for forcing a wrapper or additional argument to be added to the
23503 command. For example:
23505 command = /usr/bin/remote_exec myhost -- $address_pipe
23509 Note that &$address_pipe$& is handled specially in &%command%& when
23510 &%force_command%& is set, expanding out to the original argument vector as
23511 separate items, similarly to a Unix shell &`"$@"`& construct.
23514 .option ignore_status pipe boolean false
23515 If this option is true, the status returned by the subprocess that is set up to
23516 run the command is ignored, and Exim behaves as if zero had been returned.
23517 Otherwise, a non-zero status or termination by signal causes an error return
23518 from the transport unless the status value is one of those listed in
23519 &%temp_errors%&; these cause the delivery to be deferred and tried again later.
23521 &*Note*&: This option does not apply to timeouts, which do not return a status.
23522 See the &%timeout_defer%& option for how timeouts are handled.
23525 .option log_defer_output pipe boolean false
23526 .cindex "&(pipe)& transport" "logging output"
23527 If this option is set, and the status returned by the command is
23528 one of the codes listed in &%temp_errors%& (that is, delivery was deferred),
23529 and any output was produced on stdout or stderr, the first line of it is
23530 written to the main log.
23533 .option log_fail_output pipe boolean false
23534 If this option is set, and the command returns any output on stdout or
23535 stderr, and also ends with a return code that is neither zero nor one of
23536 the return codes listed in &%temp_errors%& (that is, the delivery
23537 failed), the first line of output is written to the main log. This
23538 option and &%log_output%& are mutually exclusive. Only one of them may
23542 .option log_output pipe boolean false
23543 If this option is set and the command returns any output on stdout or
23544 stderr, the first line of output is written to the main log, whatever
23545 the return code. This option and &%log_fail_output%& are mutually
23546 exclusive. Only one of them may be set.
23549 .option max_output pipe integer 20K
23550 This specifies the maximum amount of output that the command may produce on its
23551 standard output and standard error file combined. If the limit is exceeded, the
23552 process running the command is killed. This is intended as a safety measure to
23553 catch runaway processes. The limit is applied independently of the settings of
23554 the options that control what is done with such output (for example,
23555 &%return_output%&). Because of buffering effects, the amount of output may
23556 exceed the limit by a small amount before Exim notices.
23559 .option message_prefix pipe string&!! "see below"
23560 The string specified here is expanded and output at the start of every message.
23561 The default is unset if &%use_bsmtp%& is set. Otherwise it is
23564 From ${if def:return_path{$return_path}{MAILER-DAEMON}}\
23568 .cindex "&%tmail%&"
23569 .cindex "&""From""& line"
23570 This is required by the commonly used &_/usr/bin/vacation_& program.
23571 However, it must &'not'& be present if delivery is to the Cyrus IMAP server,
23572 or to the &%tmail%& local delivery agent. The prefix can be suppressed by
23577 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23578 &`\n`& to &`\r\n`& in &%message_prefix%&.
23581 .option message_suffix pipe string&!! "see below"
23582 The string specified here is expanded and output at the end of every message.
23583 The default is unset if &%use_bsmtp%& is set. Otherwise it is a single newline.
23584 The suffix can be suppressed by setting
23588 &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of
23589 &`\n`& to &`\r\n`& in &%message_suffix%&.
23592 .option path pipe string&!! "/bin:/usr/bin"
23593 This option is expanded and
23594 specifies the string that is set up in the PATH environment
23595 variable of the subprocess.
23596 If the &%command%& option does not yield an absolute path name, the command is
23597 sought in the PATH directories, in the usual way. &*Warning*&: This does not
23598 apply to a command specified as a transport filter.
23601 .option permit_coredump pipe boolean false
23602 Normally Exim inhibits core-dumps during delivery. If you have a need to get
23603 a core-dump of a pipe command, enable this command. This enables core-dumps
23604 during delivery and affects both the Exim binary and the pipe command run.
23605 It is recommended that this option remain off unless and until you have a need
23606 for it and that this only be enabled when needed, as the risk of excessive
23607 resource consumption can be quite high. Note also that Exim is typically
23608 installed as a setuid binary and most operating systems will inhibit coredumps
23609 of these by default, so further OS-specific action may be required.
23612 .option pipe_as_creator pipe boolean false
23613 .cindex "uid (user id)" "local delivery"
23614 If the generic &%user%& option is not set and this option is true, the delivery
23615 process is run under the uid that was in force when Exim was originally called
23616 to accept the message. If the group id is not otherwise set (via the generic
23617 &%group%& option), the gid that was in force when Exim was originally called to
23618 accept the message is used.
23621 .option restrict_to_path pipe boolean false
23622 When this option is set, any command name not listed in &%allow_commands%& must
23623 contain no slashes. The command is searched for only in the directories listed
23624 in the &%path%& option. This option is intended for use in the case when a pipe
23625 command has been generated from a user's &_.forward_& file. This is usually
23626 handled by a &(pipe)& transport called &%address_pipe%&.
23629 .option return_fail_output pipe boolean false
23630 If this option is true, and the command produced any output and ended with a
23631 return code other than zero or one of the codes listed in &%temp_errors%& (that
23632 is, the delivery failed), the output is returned in the bounce message.
23633 However, if the message has a null sender (that is, it is itself a bounce
23634 message), output from the command is discarded. This option and
23635 &%return_output%& are mutually exclusive. Only one of them may be set.
23639 .option return_output pipe boolean false
23640 If this option is true, and the command produced any output, the delivery is
23641 deemed to have failed whatever the return code from the command, and the output
23642 is returned in the bounce message. Otherwise, the output is just discarded.
23643 However, if the message has a null sender (that is, it is a bounce message),
23644 output from the command is always discarded, whatever the setting of this
23645 option. This option and &%return_fail_output%& are mutually exclusive. Only one
23646 of them may be set.
23650 .option temp_errors pipe "string list" "see below"
23651 .cindex "&(pipe)& transport" "temporary failure"
23652 This option contains either a colon-separated list of numbers, or a single
23653 asterisk. If &%ignore_status%& is false
23654 and &%return_output%& is not set,
23655 and the command exits with a non-zero return code, the failure is treated as
23656 temporary and the delivery is deferred if the return code matches one of the
23657 numbers, or if the setting is a single asterisk. Otherwise, non-zero return
23658 codes are treated as permanent errors. The default setting contains the codes
23659 defined by EX_TEMPFAIL and EX_CANTCREAT in &_sysexits.h_&. If Exim is
23660 compiled on a system that does not define these macros, it assumes values of 75
23661 and 73, respectively.
23664 .option timeout pipe time 1h
23665 If the command fails to complete within this time, it is killed. This normally
23666 causes the delivery to fail (but see &%timeout_defer%&). A zero time interval
23667 specifies no timeout. In order to ensure that any subprocesses created by the
23668 command are also killed, Exim makes the initial process a process group leader,
23669 and kills the whole process group on a timeout. However, this can be defeated
23670 if one of the processes starts a new process group.
23672 .option timeout_defer pipe boolean false
23673 A timeout in a &(pipe)& transport, either in the command that the transport
23674 runs, or in a transport filter that is associated with it, is by default
23675 treated as a hard error, and the delivery fails. However, if &%timeout_defer%&
23676 is set true, both kinds of timeout become temporary errors, causing the
23677 delivery to be deferred.
23679 .option umask pipe "octal integer" 022
23680 This specifies the umask setting for the subprocess that runs the command.
23683 .option use_bsmtp pipe boolean false
23684 .cindex "envelope sender"
23685 If this option is set true, the &(pipe)& transport writes messages in &"batch
23686 SMTP"& format, with the envelope sender and recipient(s) included as SMTP
23687 commands. If you want to include a leading HELO command with such messages,
23688 you can do so by setting the &%message_prefix%& option. See section
23689 &<<SECTbatchSMTP>>& for details of batch SMTP.
23691 .option use_classresources pipe boolean false
23692 .cindex "class resources (BSD)"
23693 This option is available only when Exim is running on FreeBSD, NetBSD, or
23694 BSD/OS. If it is set true, the &[setclassresources()]& function is used to set
23695 resource limits when a &(pipe)& transport is run to perform a delivery. The
23696 limits for the uid under which the pipe is to run are obtained from the login
23700 .option use_crlf pipe boolean false
23701 .cindex "carriage return"
23703 This option causes lines to be terminated with the two-character CRLF sequence
23704 (carriage return, linefeed) instead of just a linefeed character. In the case
23705 of batched SMTP, the byte sequence written to the pipe is then an exact image
23706 of what would be sent down a real SMTP connection.
23708 The contents of the &%message_prefix%& and &%message_suffix%& options are
23709 written verbatim, so must contain their own carriage return characters if these
23710 are needed. When &%use_bsmtp%& is not set, the default values for both
23711 &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their
23712 values must be changed to end with &`\r\n`& if &%use_crlf%& is set.
23715 .option use_shell pipe boolean false
23716 .vindex "&$pipe_addresses$&"
23717 If this option is set, it causes the command to be passed to &_/bin/sh_&
23718 instead of being run directly from the transport, as described in section
23719 &<<SECThowcommandrun>>&. This is less secure, but is needed in some situations
23720 where the command is expected to be run under a shell and cannot easily be
23721 modified. The &%allow_commands%& and &%restrict_to_path%& options, and the
23722 &`$pipe_addresses`& facility are incompatible with &%use_shell%&. The
23723 command is expanded as a single string, and handed to &_/bin/sh_& as data for
23728 .section "Using an external local delivery agent" "SECID143"
23729 .cindex "local delivery" "using an external agent"
23730 .cindex "&'procmail'&"
23731 .cindex "external local delivery"
23732 .cindex "delivery" "&'procmail'&"
23733 .cindex "delivery" "by external agent"
23734 The &(pipe)& transport can be used to pass all messages that require local
23735 delivery to a separate local delivery agent such as &%procmail%&. When doing
23736 this, care must be taken to ensure that the pipe is run under an appropriate
23737 uid and gid. In some configurations one wants this to be a uid that is trusted
23738 by the delivery agent to supply the correct sender of the message. It may be
23739 necessary to recompile or reconfigure the delivery agent so that it trusts an
23740 appropriate user. The following is an example transport and router
23741 configuration for &%procmail%&:
23746 command = /usr/local/bin/procmail -d $local_part
23750 check_string = "From "
23751 escape_string = ">From "
23760 transport = procmail_pipe
23762 In this example, the pipe is run as the local user, but with the group set to
23763 &'mail'&. An alternative is to run the pipe as a specific user such as &'mail'&
23764 or &'exim'&, but in this case you must arrange for &%procmail%& to trust that
23765 user to supply a correct sender address. If you do not specify either a
23766 &%group%& or a &%user%& option, the pipe command is run as the local user. The
23767 home directory is the user's home directory by default.
23769 &*Note*&: The command that the pipe transport runs does &'not'& begin with
23773 as shown in some &%procmail%& documentation, because Exim does not by default
23774 use a shell to run pipe commands.
23777 The next example shows a transport and a router for a system where local
23778 deliveries are handled by the Cyrus IMAP server.
23781 local_delivery_cyrus:
23783 command = /usr/cyrus/bin/deliver \
23784 -m ${substr_1:$local_part_suffix} -- $local_part
23796 local_part_suffix = .*
23797 transport = local_delivery_cyrus
23799 Note the unsetting of &%message_prefix%& and &%message_suffix%&, and the use of
23800 &%return_output%& to cause any text written by Cyrus to be returned to the
23802 .ecindex IIDpiptra1
23803 .ecindex IIDpiptra2
23806 . ////////////////////////////////////////////////////////////////////////////
23807 . ////////////////////////////////////////////////////////////////////////////
23809 .chapter "The smtp transport" "CHAPsmtptrans"
23810 .scindex IIDsmttra1 "transports" "&(smtp)&"
23811 .scindex IIDsmttra2 "&(smtp)& transport"
23812 The &(smtp)& transport delivers messages over TCP/IP connections using the SMTP
23813 or LMTP protocol. The list of hosts to try can either be taken from the address
23814 that is being processed (having been set up by the router), or specified
23815 explicitly for the transport. Timeout and retry processing (see chapter
23816 &<<CHAPretry>>&) is applied to each IP address independently.
23819 .section "Multiple messages on a single connection" "SECID144"
23820 The sending of multiple messages over a single TCP/IP connection can arise in
23824 If a message contains more than &%max_rcpt%& (see below) addresses that are
23825 routed to the same host, more than one copy of the message has to be sent to
23826 that host. In this situation, multiple copies may be sent in a single run of
23827 the &(smtp)& transport over a single TCP/IP connection. (What Exim actually
23828 does when it has too many addresses to send in one message also depends on the
23829 value of the global &%remote_max_parallel%& option. Details are given in
23830 section &<<SECToutSMTPTCP>>&.)
23832 .cindex "hints database" "remembering routing"
23833 When a message has been successfully delivered over a TCP/IP connection, Exim
23834 looks in its hints database to see if there are any other messages awaiting a
23835 connection to the same host. If there are, a new delivery process is started
23836 for one of them, and the current TCP/IP connection is passed on to it. The new
23837 process may in turn send multiple copies and possibly create yet another
23842 For each copy sent over the same TCP/IP connection, a sequence counter is
23843 incremented, and if it ever gets to the value of &%connection_max_messages%&,
23844 no further messages are sent over that connection.
23848 .section "Use of the $host and $host_address variables" "SECID145"
23850 .vindex "&$host_address$&"
23851 At the start of a run of the &(smtp)& transport, the values of &$host$& and
23852 &$host_address$& are the name and IP address of the first host on the host list
23853 passed by the router. However, when the transport is about to connect to a
23854 specific host, and while it is connected to that host, &$host$& and
23855 &$host_address$& are set to the values for that host. These are the values
23856 that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&,
23857 &%serialize_hosts%&, and the various TLS options are expanded.
23860 .section "Use of $tls_cipher and $tls_peerdn" "usecippeer"
23861 .vindex &$tls_bits$&
23862 .vindex &$tls_cipher$&
23863 .vindex &$tls_peerdn$&
23864 .vindex &$tls_sni$&
23865 At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&,
23866 &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$&
23867 are the values that were set when the message was received.
23868 These are the values that are used for options that are expanded before any
23869 SMTP connections are made. Just before each connection is made, these four
23870 variables are emptied. If TLS is subsequently started, they are set to the
23871 appropriate values for the outgoing connection, and these are the values that
23872 are in force when any authenticators are run and when the
23873 &%authenticated_sender%& option is expanded.
23875 These variables are deprecated in favour of &$tls_in_cipher$& et. al.
23876 and will be removed in a future release.
23879 .section "Private options for smtp" "SECID146"
23880 .cindex "options" "&(smtp)& transport"
23881 The private options of the &(smtp)& transport are as follows:
23884 .option address_retry_include_sender smtp boolean true
23885 .cindex "4&'xx'& responses" "retrying after"
23886 When an address is delayed because of a 4&'xx'& response to a RCPT command, it
23887 is the combination of sender and recipient that is delayed in subsequent queue
23888 runs until the retry time is reached. You can delay the recipient without
23889 reference to the sender (which is what earlier versions of Exim did), by
23890 setting &%address_retry_include_sender%& false. However, this can lead to
23891 problems with servers that regularly issue 4&'xx'& responses to RCPT commands.
23893 .option allow_localhost smtp boolean false
23894 .cindex "local host" "sending to"
23895 .cindex "fallback" "hosts specified on transport"
23896 When a host specified in &%hosts%& or &%fallback_hosts%& (see below) turns out
23897 to be the local host, or is listed in &%hosts_treat_as_local%&, delivery is
23898 deferred by default. However, if &%allow_localhost%& is set, Exim goes on to do
23899 the delivery anyway. This should be used only in special cases when the
23900 configuration ensures that no looping will result (for example, a differently
23901 configured Exim is listening on the port to which the message is sent).
23904 .option authenticated_sender smtp string&!! unset
23906 When Exim has authenticated as a client, or if &%authenticated_sender_force%&
23907 is true, this option sets a value for the AUTH= item on outgoing MAIL commands,
23908 overriding any existing authenticated sender value. If the string expansion is
23909 forced to fail, the option is ignored. Other expansion failures cause delivery
23910 to be deferred. If the result of expansion is an empty string, that is also
23913 The expansion happens after the outgoing connection has been made and TLS
23914 started, if required. This means that the &$host$&, &$host_address$&,
23915 &$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the
23916 particular connection.
23918 If the SMTP session is not authenticated, the expansion of
23919 &%authenticated_sender%& still happens (and can cause the delivery to be
23920 deferred if it fails), but no AUTH= item is added to MAIL commands
23921 unless &%authenticated_sender_force%& is true.
23923 This option allows you to use the &(smtp)& transport in LMTP mode to
23924 deliver mail to Cyrus IMAP and provide the proper local part as the
23925 &"authenticated sender"&, via a setting such as:
23927 authenticated_sender = $local_part
23929 This removes the need for IMAP subfolders to be assigned special ACLs to
23930 allow direct delivery to those subfolders.
23932 Because of expected uses such as that just described for Cyrus (when no
23933 domain is involved), there is no checking on the syntax of the provided
23937 .option authenticated_sender_force smtp boolean false
23938 If this option is set true, the &%authenticated_sender%& option's value
23939 is used for the AUTH= item on outgoing MAIL commands, even if Exim has not
23940 authenticated as a client.
23943 .option command_timeout smtp time 5m
23944 This sets a timeout for receiving a response to an SMTP command that has been
23945 sent out. It is also used when waiting for the initial banner line from the
23946 remote host. Its value must not be zero.
23949 .option connect_timeout smtp time 5m
23950 This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
23951 to a remote host. A setting of zero allows the system timeout (typically
23952 several minutes) to act. To have any effect, the value of this option must be
23953 less than the system timeout. However, it has been observed that on some
23954 systems there is no system timeout, which is why the default value for this
23955 option is 5 minutes, a value recommended by RFC 1123.
23958 .option connection_max_messages smtp integer 500
23959 .cindex "SMTP" "passed connection"
23960 .cindex "SMTP" "multiple deliveries"
23961 .cindex "multiple SMTP deliveries"
23962 This controls the maximum number of separate message deliveries that are sent
23963 over a single TCP/IP connection. If the value is zero, there is no limit.
23964 For testing purposes, this value can be overridden by the &%-oB%& command line
23968 .option dane_require_tls_ciphers smtp string&!! unset
23969 .cindex "TLS" "requiring specific ciphers for DANE"
23970 .cindex "cipher" "requiring specific"
23971 .cindex DANE "TLS ciphers"
23972 This option may be used to override &%tls_require_ciphers%& for connections
23973 where DANE has been determined to be in effect.
23974 If not set, then &%tls_require_ciphers%& will be used.
23975 Normal SMTP delivery is not able to make strong demands of TLS cipher
23976 configuration, because delivery will fall back to plaintext. Once DANE has
23977 been determined to be in effect, there is no plaintext fallback and making the
23978 TLS cipherlist configuration stronger will increase security, rather than
23979 counter-intuitively decreasing it.
23980 If the option expands to be empty or is forced to fail, then it will
23981 be treated as unset and &%tls_require_ciphers%& will be used instead.
23984 .option data_timeout smtp time 5m
23985 This sets a timeout for the transmission of each block in the data portion of
23986 the message. As a result, the overall timeout for a message depends on the size
23987 of the message. Its value must not be zero. See also &%final_timeout%&.
23990 .option dkim_canon smtp string&!! unset
23991 .option dkim_domain smtp string list&!! unset
23992 .option dkim_hash smtp string&!! sha256
23993 .option dkim_identity smtp string&!! unset
23994 .option dkim_private_key smtp string&!! unset
23995 .option dkim_selector smtp string&!! unset
23996 .option dkim_strict smtp string&!! unset
23997 .option dkim_sign_headers smtp string&!! "per RFC"
23998 .option dkim_timestamps smtp string&!! unset
23999 DKIM signing options. For details see section &<<SECDKIMSIGN>>&.
24002 .option delay_after_cutoff smtp boolean true
24003 This option controls what happens when all remote IP addresses for a given
24004 domain have been inaccessible for so long that they have passed their retry
24007 In the default state, if the next retry time has not been reached for any of
24008 them, the address is bounced without trying any deliveries. In other words,
24009 Exim delays retrying an IP address after the final cutoff time until a new
24010 retry time is reached, and can therefore bounce an address without ever trying
24011 a delivery, when machines have been down for a long time. Some people are
24012 unhappy at this prospect, so...
24014 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
24015 addresses are past their final cutoff time, Exim tries to deliver to those
24016 IP addresses that have not been tried since the message arrived. If there are
24017 none, of if they all fail, the address is bounced. In other words, it does not
24018 delay when a new message arrives, but immediately tries those expired IP
24019 addresses that haven't been tried since the message arrived. If there is a
24020 continuous stream of messages for the dead hosts, unsetting
24021 &%delay_after_cutoff%& means that there will be many more attempts to deliver
24025 .option dns_qualify_single smtp boolean true
24026 If the &%hosts%& or &%fallback_hosts%& option is being used,
24027 and the &%gethostbyname%& option is false,
24028 the RES_DEFNAMES resolver option is set. See the &%qualify_single%& option
24029 in chapter &<<CHAPdnslookup>>& for more details.
24032 .option dns_search_parents smtp boolean false
24033 If the &%hosts%& or &%fallback_hosts%& option is being used, and the
24034 &%gethostbyname%& option is false, the RES_DNSRCH resolver option is set.
24035 See the &%search_parents%& option in chapter &<<CHAPdnslookup>>& for more
24039 .option dnssec_request_domains smtp "domain list&!!" unset
24040 .cindex "MX record" "security"
24041 .cindex "DNSSEC" "MX lookup"
24042 .cindex "security" "MX lookup"
24043 .cindex "DNS" "DNSSEC"
24044 DNS lookups for domains matching &%dnssec_request_domains%& will be done with
24045 the dnssec request bit set.
24046 This applies to all of the SRV, MX, AAAA, A lookup sequence.
24050 .option dnssec_require_domains smtp "domain list&!!" unset
24051 .cindex "MX record" "security"
24052 .cindex "DNSSEC" "MX lookup"
24053 .cindex "security" "MX lookup"
24054 .cindex "DNS" "DNSSEC"
24055 DNS lookups for domains matching &%dnssec_require_domains%& will be done with
24056 the dnssec request bit set. Any returns not having the Authenticated Data bit
24057 (AD bit) set will be ignored and logged as a host-lookup failure.
24058 This applies to all of the SRV, MX, AAAA, A lookup sequence.
24062 .option dscp smtp string&!! unset
24063 .cindex "DCSP" "outbound"
24064 This option causes the DSCP value associated with a socket to be set to one
24065 of a number of fixed strings or to numeric value.
24066 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
24067 Common values include &`throughput`&, &`mincost`&, and on newer systems
24068 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
24070 The outbound packets from Exim will be marked with this value in the header
24071 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
24072 that these values will have any effect, not be stripped by networking
24073 equipment, or do much of anything without cooperation with your Network
24074 Engineer and those of all network operators between the source and destination.
24077 .option fallback_hosts smtp "string list" unset
24078 .cindex "fallback" "hosts specified on transport"
24079 String expansion is not applied to this option. The argument must be a
24080 colon-separated list of host names or IP addresses, optionally also including
24081 port numbers, though the separator can be changed, as described in section
24082 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
24083 item in a &%route_list%& setting for the &(manualroute)& router, as described
24084 in section &<<SECTformatonehostitem>>&.
24086 Fallback hosts can also be specified on routers, which associate them with the
24087 addresses they process. As for the &%hosts%& option without &%hosts_override%&,
24088 &%fallback_hosts%& specified on the transport is used only if the address does
24089 not have its own associated fallback host list. Unlike &%hosts%&, a setting of
24090 &%fallback_hosts%& on an address is not overridden by &%hosts_override%&.
24091 However, &%hosts_randomize%& does apply to fallback host lists.
24093 If Exim is unable to deliver to any of the hosts for a particular address, and
24094 the errors are not permanent rejections, the address is put on a separate
24095 transport queue with its host list replaced by the fallback hosts, unless the
24096 address was routed via MX records and the current host was in the original MX
24097 list. In that situation, the fallback host list is not used.
24099 Once normal deliveries are complete, the fallback queue is delivered by
24100 re-running the same transports with the new host lists. If several failing
24101 addresses have the same fallback hosts (and &%max_rcpt%& permits it), a single
24102 copy of the message is sent.
24104 The resolution of the host names on the fallback list is controlled by the
24105 &%gethostbyname%& option, as for the &%hosts%& option. Fallback hosts apply
24106 both to cases when the host list comes with the address and when it is taken
24107 from &%hosts%&. This option provides a &"use a smart host only if delivery
24111 .option final_timeout smtp time 10m
24112 This is the timeout that applies while waiting for the response to the final
24113 line containing just &"."& that terminates a message. Its value must not be
24116 .option gethostbyname smtp boolean false
24117 If this option is true when the &%hosts%& and/or &%fallback_hosts%& options are
24118 being used, names are looked up using &[gethostbyname()]&
24119 (or &[getipnodebyname()]& when available)
24120 instead of using the DNS. Of course, that function may in fact use the DNS, but
24121 it may also consult other sources of information such as &_/etc/hosts_&.
24123 .option gnutls_compat_mode smtp boolean unset
24124 This option controls whether GnuTLS is used in compatibility mode in an Exim
24125 server. This reduces security slightly, but improves interworking with older
24126 implementations of TLS.
24128 .option helo_data smtp string&!! "see below"
24129 .cindex "HELO" "argument, setting"
24130 .cindex "EHLO" "argument, setting"
24131 .cindex "LHLO argument setting"
24132 The value of this option is expanded after a connection to a another host has
24133 been set up. The result is used as the argument for the EHLO, HELO, or LHLO
24134 command that starts the outgoing SMTP or LMTP session. The default value of the
24139 During the expansion, the variables &$host$& and &$host_address$& are set to
24140 the identity of the remote host, and the variables &$sending_ip_address$& and
24141 &$sending_port$& are set to the local IP address and port number that are being
24142 used. These variables can be used to generate different values for different
24143 servers or different local IP addresses. For example, if you want the string
24144 that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing
24145 interface address, you could use this:
24147 helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\
24148 {$primary_hostname}}
24150 The use of &%helo_data%& applies both to sending messages and when doing
24153 .option hosts smtp "string list&!!" unset
24154 Hosts are associated with an address by a router such as &(dnslookup)&, which
24155 finds the hosts by looking up the address domain in the DNS, or by
24156 &(manualroute)&, which has lists of hosts in its configuration. However,
24157 email addresses can be passed to the &(smtp)& transport by any router, and not
24158 all of them can provide an associated list of hosts.
24160 The &%hosts%& option specifies a list of hosts to be used if the address being
24161 processed does not have any hosts associated with it. The hosts specified by
24162 &%hosts%& are also used, whether or not the address has its own hosts, if
24163 &%hosts_override%& is set.
24165 The string is first expanded, before being interpreted as a colon-separated
24166 list of host names or IP addresses, possibly including port numbers. The
24167 separator may be changed to something other than colon, as described in section
24168 &<<SECTlistconstruct>>&. Each individual item in the list is the same as an
24169 item in a &%route_list%& setting for the &(manualroute)& router, as described
24170 in section &<<SECTformatonehostitem>>&. However, note that the &`/MX`& facility
24171 of the &(manualroute)& router is not available here.
24173 If the expansion fails, delivery is deferred. Unless the failure was caused by
24174 the inability to complete a lookup, the error is logged to the panic log as
24175 well as the main log. Host names are looked up either by searching directly for
24176 address records in the DNS or by calling &[gethostbyname()]& (or
24177 &[getipnodebyname()]& when available), depending on the setting of the
24178 &%gethostbyname%& option. When Exim is compiled with IPv6 support, if a host
24179 that is looked up in the DNS has both IPv4 and IPv6 addresses, both types of
24182 During delivery, the hosts are tried in order, subject to their retry status,
24183 unless &%hosts_randomize%& is set.
24186 .option hosts_avoid_esmtp smtp "host list&!!" unset
24187 .cindex "ESMTP, avoiding use of"
24188 .cindex "HELO" "forcing use of"
24189 .cindex "EHLO" "avoiding use of"
24190 .cindex "PIPELINING" "avoiding the use of"
24191 This option is for use with broken hosts that announce ESMTP facilities (for
24192 example, PIPELINING) and then fail to implement them properly. When a host
24193 matches &%hosts_avoid_esmtp%&, Exim sends HELO rather than EHLO at the
24194 start of the SMTP session. This means that it cannot use any of the ESMTP
24195 facilities such as AUTH, PIPELINING, SIZE, and STARTTLS.
24198 .option hosts_avoid_pipelining smtp "host list&!!" unset
24199 .cindex "PIPELINING" "avoiding the use of"
24200 Exim will not use the SMTP PIPELINING extension when delivering to any host
24201 that matches this list, even if the server host advertises PIPELINING support.
24204 .option hosts_avoid_tls smtp "host list&!!" unset
24205 .cindex "TLS" "avoiding for certain hosts"
24206 Exim will not try to start a TLS session when delivering to any host that
24207 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
24209 .option hosts_verify_avoid_tls smtp "host list&!!" unset
24210 .cindex "TLS" "avoiding for certain hosts"
24211 Exim will not try to start a TLS session for a verify callout,
24212 or when delivering in cutthrough mode,
24213 to any host that matches this list.
24216 .option hosts_max_try smtp integer 5
24217 .cindex "host" "maximum number to try"
24218 .cindex "limit" "number of hosts tried"
24219 .cindex "limit" "number of MX tried"
24220 .cindex "MX record" "maximum tried"
24221 This option limits the number of IP addresses that are tried for any one
24222 delivery in cases where there are temporary delivery errors. Section
24223 &<<SECTvalhosmax>>& describes in detail how the value of this option is used.
24226 .option hosts_max_try_hardlimit smtp integer 50
24227 This is an additional check on the maximum number of IP addresses that Exim
24228 tries for any one delivery. Section &<<SECTvalhosmax>>& describes its use and
24233 .option hosts_nopass_tls smtp "host list&!!" unset
24234 .cindex "TLS" "passing connection"
24235 .cindex "multiple SMTP deliveries"
24236 .cindex "TLS" "multiple message deliveries"
24237 For any host that matches this list, a connection on which a TLS session has
24238 been started will not be passed to a new delivery process for sending another
24239 message on the same connection. See section &<<SECTmulmessam>>& for an
24240 explanation of when this might be needed.
24242 .option hosts_noproxy_tls smtp "host list&!!" *
24243 .cindex "TLS" "passing connection"
24244 .cindex "multiple SMTP deliveries"
24245 .cindex "TLS" "multiple message deliveries"
24246 For any host that matches this list, a TLS session which has
24247 been started will not be passed to a new delivery process for sending another
24248 message on the same session.
24250 The traditional implementation closes down TLS and re-starts it in the new
24251 process, on the same open TCP connection, for each successive message
24252 sent. If permitted by this option a pipe to to the new process is set up
24253 instead, and the original process maintains the TLS connection and proxies
24254 the SMTP connection from and to the new process and any subsequents.
24255 The new process has no access to TLS information, so cannot include it in
24260 .option hosts_override smtp boolean false
24261 If this option is set and the &%hosts%& option is also set, any hosts that are
24262 attached to the address are ignored, and instead the hosts specified by the
24263 &%hosts%& option are always used. This option does not apply to
24264 &%fallback_hosts%&.
24267 .option hosts_randomize smtp boolean false
24268 .cindex "randomized host list"
24269 .cindex "host" "list of; randomized"
24270 .cindex "fallback" "randomized hosts"
24271 If this option is set, and either the list of hosts is taken from the
24272 &%hosts%& or the &%fallback_hosts%& option, or the hosts supplied by the router
24273 were not obtained from MX records (this includes fallback hosts from the
24274 router), and were not randomized by the router, the order of trying the hosts
24275 is randomized each time the transport runs. Randomizing the order of a host
24276 list can be used to do crude load sharing.
24278 When &%hosts_randomize%& is true, a host list may be split into groups whose
24279 order is separately randomized. This makes it possible to set up MX-like
24280 behaviour. The boundaries between groups are indicated by an item that is just
24281 &`+`& in the host list. For example:
24283 hosts = host1:host2:host3:+:host4:host5
24285 The order of the first three hosts and the order of the last two hosts is
24286 randomized for each use, but the first three always end up before the last two.
24287 If &%hosts_randomize%& is not set, a &`+`& item in the list is ignored.
24289 .option hosts_require_auth smtp "host list&!!" unset
24290 .cindex "authentication" "required by client"
24291 This option provides a list of servers for which authentication must succeed
24292 before Exim will try to transfer a message. If authentication fails for
24293 servers which are not in this list, Exim tries to send unauthenticated. If
24294 authentication fails for one of these servers, delivery is deferred. This
24295 temporary error is detectable in the retry rules, so it can be turned into a
24296 hard failure if required. See also &%hosts_try_auth%&, and chapter
24297 &<<CHAPSMTPAUTH>>& for details of authentication.
24300 .option hosts_request_ocsp smtp "host list&!!" *
24301 .cindex "TLS" "requiring for certain servers"
24302 Exim will request a Certificate Status on a
24303 TLS session for any host that matches this list.
24304 &%tls_verify_certificates%& should also be set for the transport.
24306 .option hosts_require_dane smtp "host list&!!" unset
24307 .cindex DANE "transport options"
24308 .cindex DANE "requiring for certain servers"
24309 If built with DANE support, Exim will require that a DNSSEC-validated
24310 TLSA record is present for any host matching the list,
24311 and that a DANE-verified TLS connection is made.
24312 There will be no fallback to in-clear communication.
24313 See section &<<SECDANE>>&.
24315 .option hosts_require_ocsp smtp "host list&!!" unset
24316 .cindex "TLS" "requiring for certain servers"
24317 Exim will request, and check for a valid Certificate Status being given, on a
24318 TLS session for any host that matches this list.
24319 &%tls_verify_certificates%& should also be set for the transport.
24321 .option hosts_require_tls smtp "host list&!!" unset
24322 .cindex "TLS" "requiring for certain servers"
24323 Exim will insist on using a TLS session when delivering to any host that
24324 matches this list. See chapter &<<CHAPTLS>>& for details of TLS.
24325 &*Note*&: This option affects outgoing mail only. To insist on TLS for
24326 incoming messages, use an appropriate ACL.
24328 .option hosts_try_auth smtp "host list&!!" unset
24329 .cindex "authentication" "optional in client"
24330 This option provides a list of servers to which, provided they announce
24331 authentication support, Exim will attempt to authenticate as a client when it
24332 connects. If authentication fails, Exim will try to transfer the message
24333 unauthenticated. See also &%hosts_require_auth%&, and chapter
24334 &<<CHAPSMTPAUTH>>& for details of authentication.
24336 .option hosts_try_chunking smtp "host list&!!" *
24337 .cindex CHUNKING "enabling, in client"
24338 .cindex BDAT "SMTP command"
24339 .cindex "RFC 3030" "CHUNKING"
24340 This option provides a list of servers to which, provided they announce
24341 CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
24342 BDAT will not be used in conjunction with a transport filter.
24344 .option hosts_try_dane smtp "host list&!!" unset
24345 .cindex DANE "transport options"
24346 .cindex DANE "attempting for certain servers"
24347 If built with DANE support, Exim will lookup a
24348 TLSA record for any host matching the list.
24349 If found and verified by DNSSEC,
24350 a DANE-verified TLS connection is made to that host;
24351 there will be no fallback to in-clear communication.
24352 See section &<<SECDANE>>&.
24354 .option hosts_try_fastopen smtp "host list&!!" unset
24355 .cindex "fast open, TCP" "enabling, in client"
24356 .cindex "TCP Fast Open" "enabling, in client"
24357 .cindex "RFC 7413" "TCP Fast Open"
24358 This option provides a list of servers to which, provided
24359 the facility is supported by this system, Exim will attempt to
24360 perform a TCP Fast Open.
24361 No data is sent on the SYN segment but, if the remote server also
24362 supports the facility, it can send its SMTP banner immediately after
24363 the SYN,ACK segment. This can save up to one round-trip time.
24365 The facility is only active for previously-contacted servers,
24366 as the initiator must present a cookie in the SYN segment.
24368 On (at least some) current Linux distributions the facility must be enabled
24369 in the kernel by the sysadmin before the support is usable.
24370 There is no option for control of the server side; if the system supports
24371 it it is always enabled. Note that lengthy operations in the connect ACL,
24372 such as DNSBL lookups, will still delay the emission of the SMTP banner.
24374 .option hosts_try_prdr smtp "host list&!!" *
24375 .cindex "PRDR" "enabling, optional in client"
24376 This option provides a list of servers to which, provided they announce
24377 PRDR support, Exim will attempt to negotiate PRDR
24378 for multi-recipient messages.
24379 The option can usually be left as default.
24381 .option interface smtp "string list&!!" unset
24382 .cindex "bind IP address"
24383 .cindex "IP address" "binding"
24385 .vindex "&$host_address$&"
24386 This option specifies which interface to bind to when making an outgoing SMTP
24387 call. The value is an IP address, not an interface name such as
24388 &`eth0`&. Do not confuse this with the interface address that was used when a
24389 message was received, which is in &$received_ip_address$&, formerly known as
24390 &$interface_address$&. The name was changed to minimize confusion with the
24391 outgoing interface address. There is no variable that contains an outgoing
24392 interface address because, unless it is set by this option, its value is
24395 During the expansion of the &%interface%& option the variables &$host$& and
24396 &$host_address$& refer to the host to which a connection is about to be made
24397 during the expansion of the string. Forced expansion failure, or an empty
24398 string result causes the option to be ignored. Otherwise, after expansion, the
24399 string must be a list of IP addresses, colon-separated by default, but the
24400 separator can be changed in the usual way. For example:
24402 interface = <; 192.168.123.123 ; 3ffe:ffff:836f::fe86:a061
24404 The first interface of the correct type (IPv4 or IPv6) is used for the outgoing
24405 connection. If none of them are the correct type, the option is ignored. If
24406 &%interface%& is not set, or is ignored, the system's IP functions choose which
24407 interface to use if the host has more than one.
24410 .option keepalive smtp boolean true
24411 .cindex "keepalive" "on outgoing connection"
24412 This option controls the setting of SO_KEEPALIVE on outgoing TCP/IP socket
24413 connections. When set, it causes the kernel to probe idle connections
24414 periodically, by sending packets with &"old"& sequence numbers. The other end
24415 of the connection should send a acknowledgment if the connection is still okay
24416 or a reset if the connection has been aborted. The reason for doing this is
24417 that it has the beneficial effect of freeing up certain types of connection
24418 that can get stuck when the remote host is disconnected without tidying up the
24419 TCP/IP call properly. The keepalive mechanism takes several hours to detect
24423 .option lmtp_ignore_quota smtp boolean false
24424 .cindex "LMTP" "ignoring quota errors"
24425 If this option is set true when the &%protocol%& option is set to &"lmtp"&, the
24426 string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server
24427 has advertised support for IGNOREQUOTA in its response to the LHLO command.
24429 .option max_rcpt smtp integer 100
24430 .cindex "RCPT" "maximum number of outgoing"
24431 This option limits the number of RCPT commands that are sent in a single
24432 SMTP message transaction. Each set of addresses is treated independently, and
24433 so can cause parallel connections to the same host if &%remote_max_parallel%&
24437 .option multi_domain smtp boolean&!! true
24438 .vindex "&$domain$&"
24439 When this option is set, the &(smtp)& transport can handle a number of
24440 addresses containing a mixture of different domains provided they all resolve
24441 to the same list of hosts. Turning the option off restricts the transport to
24442 handling only one domain at a time. This is useful if you want to use
24443 &$domain$& in an expansion for the transport, because it is set only when there
24444 is a single domain involved in a remote delivery.
24446 It is expanded per-address and can depend on any of
24447 &$address_data$&, &$domain_data$&, &$local_part_data$&,
24448 &$host$&, &$host_address$& and &$host_port$&.
24450 .option port smtp string&!! "see below"
24451 .cindex "port" "sending TCP/IP"
24452 .cindex "TCP/IP" "setting outgoing port"
24453 This option specifies the TCP/IP port on the server to which Exim connects.
24454 &*Note:*& Do not confuse this with the port that was used when a message was
24455 received, which is in &$received_port$&, formerly known as &$interface_port$&.
24456 The name was changed to minimize confusion with the outgoing port. There is no
24457 variable that contains an outgoing port.
24459 If the value of this option begins with a digit it is taken as a port number;
24460 otherwise it is looked up using &[getservbyname()]&. The default value is
24461 normally &"smtp"&, but if &%protocol%& is set to &"lmtp"&, the default is
24462 &"lmtp"&. If the expansion fails, or if a port number cannot be found, delivery
24467 .option protocol smtp string smtp
24468 .cindex "LMTP" "over TCP/IP"
24469 .cindex "ssmtp protocol" "outbound"
24470 .cindex "TLS" "SSL-on-connect outbound"
24472 If this option is set to &"lmtp"& instead of &"smtp"&, the default value for
24473 the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP
24474 protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local
24475 deliveries into closed message stores. Exim also has support for running LMTP
24476 over a pipe to a local process &-- see chapter &<<CHAPLMTP>>&.
24478 If this option is set to &"smtps"&, the default value for the &%port%& option
24479 changes to &"smtps"&, and the transport initiates TLS immediately after
24480 connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
24481 The Internet standards bodies strongly discourage use of this mode.
24484 .option retry_include_ip_address smtp boolean&!! true
24485 Exim normally includes both the host name and the IP address in the key it
24486 constructs for indexing retry data after a temporary delivery failure. This
24487 means that when one of several IP addresses for a host is failing, it gets
24488 tried periodically (controlled by the retry rules), but use of the other IP
24489 addresses is not affected.
24491 However, in some dialup environments hosts are assigned a different IP address
24492 each time they connect. In this situation the use of the IP address as part of
24493 the retry key leads to undesirable behaviour. Setting this option false causes
24494 Exim to use only the host name.
24495 Since it is expanded it can be made to depend on the host or domain.
24498 .option serialize_hosts smtp "host list&!!" unset
24499 .cindex "serializing connections"
24500 .cindex "host" "serializing connections"
24501 Because Exim operates in a distributed manner, if several messages for the same
24502 host arrive at around the same time, more than one simultaneous connection to
24503 the remote host can occur. This is not usually a problem except when there is a
24504 slow link between the hosts. In that situation it may be helpful to restrict
24505 Exim to one connection at a time. This can be done by setting
24506 &%serialize_hosts%& to match the relevant hosts.
24508 .cindex "hints database" "serializing deliveries to a host"
24509 Exim implements serialization by means of a hints database in which a record is
24510 written whenever a process connects to one of the restricted hosts. The record
24511 is deleted when the connection is completed. Obviously there is scope for
24512 records to get left lying around if there is a system or program crash. To
24513 guard against this, Exim ignores any records that are more than six hours old.
24515 If you set up this kind of serialization, you should also arrange to delete the
24516 relevant hints database whenever your system reboots. The names of the files
24517 start with &_misc_& and they are kept in the &_spool/db_& directory. There
24518 may be one or two files, depending on the type of DBM in use. The same files
24519 are used for ETRN serialization.
24521 See also the &%max_parallel%& generic transport option.
24524 .option size_addition smtp integer 1024
24525 .cindex "SMTP" "SIZE"
24526 .cindex "message" "size issue for transport filter"
24527 .cindex "size" "of message"
24528 .cindex "transport" "filter"
24529 .cindex "filter" "transport filter"
24530 If a remote SMTP server indicates that it supports the SIZE option of the
24531 MAIL command, Exim uses this to pass over the message size at the start of
24532 an SMTP transaction. It adds the value of &%size_addition%& to the value it
24533 sends, to allow for headers and other text that may be added during delivery by
24534 configuration options or in a transport filter. It may be necessary to increase
24535 this if a lot of text is added to messages.
24537 Alternatively, if the value of &%size_addition%& is set negative, it disables
24538 the use of the SIZE option altogether.
24541 .option socks_proxy smtp string&!! unset
24542 .cindex proxy SOCKS
24543 This option enables use of SOCKS proxies for connections made by the
24544 transport. For details see section &<<SECTproxySOCKS>>&.
24547 .option tls_certificate smtp string&!! unset
24548 .cindex "TLS" "client certificate, location of"
24549 .cindex "certificate" "client, location of"
24551 .vindex "&$host_address$&"
24552 The value of this option must be the absolute path to a file which contains the
24553 client's certificate, for possible use when sending a message over an encrypted
24554 connection. The values of &$host$& and &$host_address$& are set to the name and
24555 address of the server during the expansion. See chapter &<<CHAPTLS>>& for
24558 &*Note*&: This option must be set if you want Exim to be able to use a TLS
24559 certificate when sending messages as a client. The global option of the same
24560 name specifies the certificate for Exim as a server; it is not automatically
24561 assumed that the same certificate should be used when Exim is operating as a
24565 .option tls_crl smtp string&!! unset
24566 .cindex "TLS" "client certificate revocation list"
24567 .cindex "certificate" "revocation list for client"
24568 This option specifies a certificate revocation list. The expanded value must
24569 be the name of a file that contains a CRL in PEM format.
24572 .option tls_dh_min_bits smtp integer 1024
24573 .cindex "TLS" "Diffie-Hellman minimum acceptable size"
24574 When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman
24575 key agreement is negotiated, the server will provide a large prime number
24576 for use. This option establishes the minimum acceptable size of that number.
24577 If the parameter offered by the server is too small, then the TLS handshake
24580 Only supported when using GnuTLS.
24583 .option tls_privatekey smtp string&!! unset
24584 .cindex "TLS" "client private key, location of"
24586 .vindex "&$host_address$&"
24587 The value of this option must be the absolute path to a file which contains the
24588 client's private key. This is used when sending a message over an encrypted
24589 connection using a client certificate. The values of &$host$& and
24590 &$host_address$& are set to the name and address of the server during the
24591 expansion. If this option is unset, or the expansion is forced to fail, or the
24592 result is an empty string, the private key is assumed to be in the same file as
24593 the certificate. See chapter &<<CHAPTLS>>& for details of TLS.
24596 .option tls_require_ciphers smtp string&!! unset
24597 .cindex "TLS" "requiring specific ciphers"
24598 .cindex "cipher" "requiring specific"
24600 .vindex "&$host_address$&"
24601 The value of this option must be a list of permitted cipher suites, for use
24602 when setting up an outgoing encrypted connection. (There is a global option of
24603 the same name for controlling incoming connections.) The values of &$host$& and
24604 &$host_address$& are set to the name and address of the server during the
24605 expansion. See chapter &<<CHAPTLS>>& for details of TLS; note that this option
24606 is used in different ways by OpenSSL and GnuTLS (see sections
24607 &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&). For GnuTLS, the order of the
24608 ciphers is a preference order.
24612 .option tls_sni smtp string&!! unset
24613 .cindex "TLS" "Server Name Indication"
24614 .vindex "&$tls_sni$&"
24615 If this option is set then it sets the $tls_out_sni variable and causes any
24616 TLS session to pass this value as the Server Name Indication extension to
24617 the remote side, which can be used by the remote side to select an appropriate
24618 certificate and private key for the session.
24620 See &<<SECTtlssni>>& for more information.
24622 Note that for OpenSSL, this feature requires a build of OpenSSL that supports
24628 .option tls_tempfail_tryclear smtp boolean true
24629 .cindex "4&'xx'& responses" "to STARTTLS"
24630 When the server host is not in &%hosts_require_tls%&, and there is a problem in
24631 setting up a TLS session, this option determines whether or not Exim should try
24632 to deliver the message unencrypted. If it is set false, delivery to the
24633 current host is deferred; if there are other hosts, they are tried. If this
24634 option is set true, Exim attempts to deliver unencrypted after a 4&'xx'&
24635 response to STARTTLS. Also, if STARTTLS is accepted, but the subsequent
24636 TLS negotiation fails, Exim closes the current connection (because it is in an
24637 unknown state), opens a new one to the same host, and then tries the delivery
24641 .option tls_try_verify_hosts smtp "host list&!!" *
24642 .cindex "TLS" "server certificate verification"
24643 .cindex "certificate" "verification of server"
24644 This option gives a list of hosts for which, on encrypted connections,
24645 certificate verification will be tried but need not succeed.
24646 The &%tls_verify_certificates%& option must also be set.
24647 Note that unless the host is in this list
24648 TLS connections will be denied to hosts using self-signed certificates
24649 when &%tls_verify_certificates%& is matched.
24650 The &$tls_out_certificate_verified$& variable is set when
24651 certificate verification succeeds.
24654 .option tls_verify_cert_hostnames smtp "host list&!!" *
24655 .cindex "TLS" "server certificate hostname verification"
24656 .cindex "certificate" "verification of server"
24657 This option give a list of hosts for which,
24658 while verifying the server certificate,
24659 checks will be included on the host name
24660 (note that this will generally be the result of a DNS MX lookup)
24661 versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted
24662 limited to being the initial component of a 3-or-more component FQDN.
24664 There is no equivalent checking on client certificates.
24667 .option tls_verify_certificates smtp string&!! system
24668 .cindex "TLS" "server certificate verification"
24669 .cindex "certificate" "verification of server"
24671 .vindex "&$host_address$&"
24672 The value of this option must be either the
24674 or the absolute path to
24675 a file or directory containing permitted certificates for servers,
24676 for use when setting up an encrypted connection.
24678 The "system" value for the option will use a location compiled into the SSL library.
24679 This is not available for GnuTLS versions preceding 3.0.20; a value of "system"
24680 is taken as empty and an explicit location
24683 The use of a directory for the option value is not available for GnuTLS versions
24684 preceding 3.3.6 and a single file must be used.
24686 With OpenSSL the certificates specified
24688 either by file or directory
24689 are added to those given by the system default location.
24691 The values of &$host$& and
24692 &$host_address$& are set to the name and address of the server during the
24693 expansion of this option. See chapter &<<CHAPTLS>>& for details of TLS.
24695 For back-compatibility,
24696 if neither tls_verify_hosts nor tls_try_verify_hosts are set
24697 (a single-colon empty list counts as being set)
24698 and certificate verification fails the TLS connection is closed.
24701 .option tls_verify_hosts smtp "host list&!!" unset
24702 .cindex "TLS" "server certificate verification"
24703 .cindex "certificate" "verification of server"
24704 This option gives a list of hosts for which, on encrypted connections,
24705 certificate verification must succeed.
24706 The &%tls_verify_certificates%& option must also be set.
24707 If both this option and &%tls_try_verify_hosts%& are unset
24708 operation is as if this option selected all hosts.
24713 .section "How the limits for the number of hosts to try are used" &&&
24715 .cindex "host" "maximum number to try"
24716 .cindex "limit" "hosts; maximum number tried"
24717 There are two options that are concerned with the number of hosts that are
24718 tried when an SMTP delivery takes place. They are &%hosts_max_try%& and
24719 &%hosts_max_try_hardlimit%&.
24722 The &%hosts_max_try%& option limits the number of hosts that are tried
24723 for a single delivery. However, despite the term &"host"& in its name, the
24724 option actually applies to each IP address independently. In other words, a
24725 multihomed host is treated as several independent hosts, just as it is for
24728 Many of the larger ISPs have multiple MX records which often point to
24729 multihomed hosts. As a result, a list of a dozen or more IP addresses may be
24730 created as a result of routing one of these domains.
24732 Trying every single IP address on such a long list does not seem sensible; if
24733 several at the top of the list fail, it is reasonable to assume there is some
24734 problem that is likely to affect all of them. Roughly speaking, the value of
24735 &%hosts_max_try%& is the maximum number that are tried before deferring the
24736 delivery. However, the logic cannot be quite that simple.
24738 Firstly, IP addresses that are skipped because their retry times have not
24739 arrived do not count, and in addition, addresses that are past their retry
24740 limits are also not counted, even when they are tried. This means that when
24741 some IP addresses are past their retry limits, more than the value of
24742 &%hosts_max_retry%& may be tried. The reason for this behaviour is to ensure
24743 that all IP addresses are considered before timing out an email address (but
24744 see below for an exception).
24746 Secondly, when the &%hosts_max_try%& limit is reached, Exim looks down the host
24747 list to see if there is a subsequent host with a different (higher valued) MX.
24748 If there is, that host is considered next, and the current IP address is used
24749 but not counted. This behaviour helps in the case of a domain with a retry rule
24750 that hardly ever delays any hosts, as is now explained:
24752 Consider the case of a long list of hosts with one MX value, and a few with a
24753 higher MX value. If &%hosts_max_try%& is small (the default is 5) only a few
24754 hosts at the top of the list are tried at first. With the default retry rule,
24755 which specifies increasing retry times, the higher MX hosts are eventually
24756 tried when those at the top of the list are skipped because they have not
24757 reached their retry times.
24759 However, it is common practice to put a fixed short retry time on domains for
24760 large ISPs, on the grounds that their servers are rarely down for very long.
24761 Unfortunately, these are exactly the domains that tend to resolve to long lists
24762 of hosts. The short retry time means that the lowest MX hosts are tried every
24763 time. The attempts may be in a different order because of random sorting, but
24764 without the special MX check, the higher MX hosts would never be tried until
24765 all the lower MX hosts had timed out (which might be several days), because
24766 there are always some lower MX hosts that have reached their retry times. With
24767 the special check, Exim considers at least one IP address from each MX value at
24768 every delivery attempt, even if the &%hosts_max_try%& limit has already been
24771 The above logic means that &%hosts_max_try%& is not a hard limit, and in
24772 particular, Exim normally eventually tries all the IP addresses before timing
24773 out an email address. When &%hosts_max_try%& was implemented, this seemed a
24774 reasonable thing to do. Recently, however, some lunatic DNS configurations have
24775 been set up with hundreds of IP addresses for some domains. It can
24776 take a very long time indeed for an address to time out in these cases.
24778 The &%hosts_max_try_hardlimit%& option was added to help with this problem.
24779 Exim never tries more than this number of IP addresses; if it hits this limit
24780 and they are all timed out, the email address is bounced, even though not all
24781 possible IP addresses have been tried.
24782 .ecindex IIDsmttra1
24783 .ecindex IIDsmttra2
24789 . ////////////////////////////////////////////////////////////////////////////
24790 . ////////////////////////////////////////////////////////////////////////////
24792 .chapter "Address rewriting" "CHAPrewrite"
24793 .scindex IIDaddrew "rewriting" "addresses"
24794 There are some circumstances in which Exim automatically rewrites domains in
24795 addresses. The two most common are when an address is given without a domain
24796 (referred to as an &"unqualified address"&) or when an address contains an
24797 abbreviated domain that is expanded by DNS lookup.
24799 Unqualified envelope addresses are accepted only for locally submitted
24800 messages, or for messages that are received from hosts matching
24801 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
24802 appropriate. Unqualified addresses in header lines are qualified if they are in
24803 locally submitted messages, or messages from hosts that are permitted to send
24804 unqualified envelope addresses. Otherwise, unqualified addresses in header
24805 lines are neither qualified nor rewritten.
24807 One situation in which Exim does &'not'& automatically rewrite a domain is
24808 when it is the name of a CNAME record in the DNS. The older RFCs suggest that
24809 such a domain should be rewritten using the &"canonical"& name, and some MTAs
24810 do this. The new RFCs do not contain this suggestion.
24813 .section "Explicitly configured address rewriting" "SECID147"
24814 This chapter describes the rewriting rules that can be used in the
24815 main rewrite section of the configuration file, and also in the generic
24816 &%headers_rewrite%& option that can be set on any transport.
24818 Some people believe that configured address rewriting is a Mortal Sin.
24819 Others believe that life is not possible without it. Exim provides the
24820 facility; you do not have to use it.
24822 The main rewriting rules that appear in the &"rewrite"& section of the
24823 configuration file are applied to addresses in incoming messages, both envelope
24824 addresses and addresses in header lines. Each rule specifies the types of
24825 address to which it applies.
24827 Whether or not addresses in header lines are rewritten depends on the origin of
24828 the headers and the type of rewriting. Global rewriting, that is, rewriting
24829 rules from the rewrite section of the configuration file, is applied only to
24830 those headers that were received with the message. Header lines that are added
24831 by ACLs or by a system filter or by individual routers or transports (which
24832 are specific to individual recipient addresses) are not rewritten by the global
24835 Rewriting at transport time, by means of the &%headers_rewrite%& option,
24836 applies all headers except those added by routers and transports. That is, as
24837 well as the headers that were received with the message, it also applies to
24838 headers that were added by an ACL or a system filter.
24841 In general, rewriting addresses from your own system or domain has some
24842 legitimacy. Rewriting other addresses should be done only with great care and
24843 in special circumstances. The author of Exim believes that rewriting should be
24844 used sparingly, and mainly for &"regularizing"& addresses in your own domains.
24845 Although it can sometimes be used as a routing tool, this is very strongly
24848 There are two commonly encountered circumstances where rewriting is used, as
24849 illustrated by these examples:
24852 The company whose domain is &'hitch.fict.example'& has a number of hosts that
24853 exchange mail with each other behind a firewall, but there is only a single
24854 gateway to the outer world. The gateway rewrites &'*.hitch.fict.example'& as
24855 &'hitch.fict.example'& when sending mail off-site.
24857 A host rewrites the local parts of its own users so that, for example,
24858 &'fp42@hitch.fict.example'& becomes &'Ford.Prefect@hitch.fict.example'&.
24863 .section "When does rewriting happen?" "SECID148"
24864 .cindex "rewriting" "timing of"
24865 .cindex "&ACL;" "rewriting addresses in"
24866 Configured address rewriting can take place at several different stages of a
24867 message's processing.
24869 .vindex "&$sender_address$&"
24870 At the start of an ACL for MAIL, the sender address may have been rewritten
24871 by a special SMTP-time rewrite rule (see section &<<SECTrewriteS>>&), but no
24872 ordinary rewrite rules have yet been applied. If, however, the sender address
24873 is verified in the ACL, it is rewritten before verification, and remains
24874 rewritten thereafter. The subsequent value of &$sender_address$& is the
24875 rewritten address. This also applies if sender verification happens in a
24876 RCPT ACL. Otherwise, when the sender address is not verified, it is
24877 rewritten as soon as a message's header lines have been received.
24879 .vindex "&$domain$&"
24880 .vindex "&$local_part$&"
24881 Similarly, at the start of an ACL for RCPT, the current recipient's address
24882 may have been rewritten by a special SMTP-time rewrite rule, but no ordinary
24883 rewrite rules have yet been applied to it. However, the behaviour is different
24884 from the sender address when a recipient is verified. The address is rewritten
24885 for the verification, but the rewriting is not remembered at this stage. The
24886 value of &$local_part$& and &$domain$& after verification are always the same
24887 as they were before (that is, they contain the unrewritten &-- except for
24888 SMTP-time rewriting &-- address).
24890 As soon as a message's header lines have been received, all the envelope
24891 recipient addresses are permanently rewritten, and rewriting is also applied to
24892 the addresses in the header lines (if configured). This happens before adding
24893 any header lines that were specified in MAIL or RCPT ACLs, and
24894 .cindex "&[local_scan()]& function" "address rewriting; timing of"
24895 before the DATA ACL and &[local_scan()]& functions are run.
24897 When an address is being routed, either for delivery or for verification,
24898 rewriting is applied immediately to child addresses that are generated by
24899 redirection, unless &%no_rewrite%& is set on the router.
24901 .cindex "envelope sender" "rewriting at transport time"
24902 .cindex "rewriting" "at transport time"
24903 .cindex "header lines" "rewriting at transport time"
24904 At transport time, additional rewriting of addresses in header lines can be
24905 specified by setting the generic &%headers_rewrite%& option on a transport.
24906 This option contains rules that are identical in form to those in the rewrite
24907 section of the configuration file. They are applied to the original message
24908 header lines and any that were added by ACLs or a system filter. They are not
24909 applied to header lines that are added by routers or the transport.
24911 The outgoing envelope sender can be rewritten by means of the &%return_path%&
24912 transport option. However, it is not possible to rewrite envelope recipients at
24918 .section "Testing the rewriting rules that apply on input" "SECID149"
24919 .cindex "rewriting" "testing"
24920 .cindex "testing" "rewriting"
24921 Exim's input rewriting configuration appears in a part of the run time
24922 configuration file headed by &"begin rewrite"&. It can be tested by the
24923 &%-brw%& command line option. This takes an address (which can be a full RFC
24924 2822 address) as its argument. The output is a list of how the address would be
24925 transformed by the rewriting rules for each of the different places it might
24926 appear in an incoming message, that is, for each different header and for the
24927 envelope sender and recipient fields. For example,
24929 exim -brw ph10@exim.workshop.example
24931 might produce the output
24933 sender: Philip.Hazel@exim.workshop.example
24934 from: Philip.Hazel@exim.workshop.example
24935 to: ph10@exim.workshop.example
24936 cc: ph10@exim.workshop.example
24937 bcc: ph10@exim.workshop.example
24938 reply-to: Philip.Hazel@exim.workshop.example
24939 env-from: Philip.Hazel@exim.workshop.example
24940 env-to: ph10@exim.workshop.example
24942 which shows that rewriting has been set up for that address when used in any of
24943 the source fields, but not when it appears as a recipient address. At the
24944 present time, there is no equivalent way of testing rewriting rules that are
24945 set for a particular transport.
24948 .section "Rewriting rules" "SECID150"
24949 .cindex "rewriting" "rules"
24950 The rewrite section of the configuration file consists of lines of rewriting
24953 <&'source pattern'&> <&'replacement'&> <&'flags'&>
24955 Rewriting rules that are specified for the &%headers_rewrite%& generic
24956 transport option are given as a colon-separated list. Each item in the list
24957 takes the same form as a line in the main rewriting configuration (except that
24958 any colons must be doubled, of course).
24960 The formats of source patterns and replacement strings are described below.
24961 Each is terminated by white space, unless enclosed in double quotes, in which
24962 case normal quoting conventions apply inside the quotes. The flags are single
24963 characters which may appear in any order. Spaces and tabs between them are
24966 For each address that could potentially be rewritten, the rules are scanned in
24967 order, and replacements for the address from earlier rules can themselves be
24968 replaced by later rules (but see the &"q"& and &"R"& flags).
24970 The order in which addresses are rewritten is undefined, may change between
24971 releases, and must not be relied on, with one exception: when a message is
24972 received, the envelope sender is always rewritten first, before any header
24973 lines are rewritten. For example, the replacement string for a rewrite of an
24974 address in &'To:'& must not assume that the message's address in &'From:'& has
24975 (or has not) already been rewritten. However, a rewrite of &'From:'& may assume
24976 that the envelope sender has already been rewritten.
24978 .vindex "&$domain$&"
24979 .vindex "&$local_part$&"
24980 The variables &$local_part$& and &$domain$& can be used in the replacement
24981 string to refer to the address that is being rewritten. Note that lookup-driven
24982 rewriting can be done by a rule of the form
24986 where the lookup key uses &$1$& and &$2$& or &$local_part$& and &$domain$& to
24987 refer to the address that is being rewritten.
24990 .section "Rewriting patterns" "SECID151"
24991 .cindex "rewriting" "patterns"
24992 .cindex "address list" "in a rewriting pattern"
24993 The source pattern in a rewriting rule is any item which may appear in an
24994 address list (see section &<<SECTaddresslist>>&). It is in fact processed as a
24995 single-item address list, which means that it is expanded before being tested
24996 against the address. As always, if you use a regular expression as a pattern,
24997 you must take care to escape dollar and backslash characters, or use the &`\N`&
24998 facility to suppress string expansion within the regular expression.
25000 Domains in patterns should be given in lower case. Local parts in patterns are
25001 case-sensitive. If you want to do case-insensitive matching of local parts, you
25002 can use a regular expression that starts with &`^(?i)`&.
25004 .cindex "numerical variables (&$1$& &$2$& etc)" "in rewriting rules"
25005 After matching, the numerical variables &$1$&, &$2$&, etc. may be set,
25006 depending on the type of match which occurred. These can be used in the
25007 replacement string to insert portions of the incoming address. &$0$& always
25008 refers to the complete incoming address. When a regular expression is used, the
25009 numerical variables are set from its capturing subexpressions. For other types
25010 of pattern they are set as follows:
25013 If a local part or domain starts with an asterisk, the numerical variables
25014 refer to the character strings matched by asterisks, with &$1$& associated with
25015 the first asterisk, and &$2$& with the second, if present. For example, if the
25018 *queen@*.fict.example
25020 is matched against the address &'hearts-queen@wonderland.fict.example'& then
25022 $0 = hearts-queen@wonderland.fict.example
25026 Note that if the local part does not start with an asterisk, but the domain
25027 does, it is &$1$& that contains the wild part of the domain.
25030 If the domain part of the pattern is a partial lookup, the wild and fixed parts
25031 of the domain are placed in the next available numerical variables. Suppose,
25032 for example, that the address &'foo@bar.baz.example'& is processed by a
25033 rewriting rule of the form
25035 &`*@partial-dbm;/some/dbm/file`& <&'replacement string'&>
25037 and the key in the file that matches the domain is &`*.baz.example`&. Then
25043 If the address &'foo@baz.example'& is looked up, this matches the same
25044 wildcard file entry, and in this case &$2$& is set to the empty string, but
25045 &$3$& is still set to &'baz.example'&. If a non-wild key is matched in a
25046 partial lookup, &$2$& is again set to the empty string and &$3$& is set to the
25047 whole domain. For non-partial domain lookups, no numerical variables are set.
25051 .section "Rewriting replacements" "SECID152"
25052 .cindex "rewriting" "replacements"
25053 If the replacement string for a rule is a single asterisk, addresses that
25054 match the pattern and the flags are &'not'& rewritten, and no subsequent
25055 rewriting rules are scanned. For example,
25057 hatta@lookingglass.fict.example * f
25059 specifies that &'hatta@lookingglass.fict.example'& is never to be rewritten in
25062 .vindex "&$domain$&"
25063 .vindex "&$local_part$&"
25064 If the replacement string is not a single asterisk, it is expanded, and must
25065 yield a fully qualified address. Within the expansion, the variables
25066 &$local_part$& and &$domain$& refer to the address that is being rewritten.
25067 Any letters they contain retain their original case &-- they are not lower
25068 cased. The numerical variables are set up according to the type of pattern that
25069 matched the address, as described above. If the expansion is forced to fail by
25070 the presence of &"fail"& in a conditional or lookup item, rewriting by the
25071 current rule is abandoned, but subsequent rules may take effect. Any other
25072 expansion failure causes the entire rewriting operation to be abandoned, and an
25073 entry written to the panic log.
25077 .section "Rewriting flags" "SECID153"
25078 There are three different kinds of flag that may appear on rewriting rules:
25081 Flags that specify which headers and envelope addresses to rewrite: E, F, T, b,
25084 A flag that specifies rewriting at SMTP time: S.
25086 Flags that control the rewriting process: Q, q, R, w.
25089 For rules that are part of the &%headers_rewrite%& generic transport option,
25090 E, F, T, and S are not permitted.
25094 .section "Flags specifying which headers and envelope addresses to rewrite" &&&
25096 .cindex "rewriting" "flags"
25097 If none of the following flag letters, nor the &"S"& flag (see section
25098 &<<SECTrewriteS>>&) are present, a main rewriting rule applies to all headers
25099 and to both the sender and recipient fields of the envelope, whereas a
25100 transport-time rewriting rule just applies to all headers. Otherwise, the
25101 rewriting rule is skipped unless the relevant addresses are being processed.
25103 &`E`& rewrite all envelope fields
25104 &`F`& rewrite the envelope From field
25105 &`T`& rewrite the envelope To field
25106 &`b`& rewrite the &'Bcc:'& header
25107 &`c`& rewrite the &'Cc:'& header
25108 &`f`& rewrite the &'From:'& header
25109 &`h`& rewrite all headers
25110 &`r`& rewrite the &'Reply-To:'& header
25111 &`s`& rewrite the &'Sender:'& header
25112 &`t`& rewrite the &'To:'& header
25114 "All headers" means all of the headers listed above that can be selected
25115 individually, plus their &'Resent-'& versions. It does not include
25116 other headers such as &'Subject:'& etc.
25118 You should be particularly careful about rewriting &'Sender:'& headers, and
25119 restrict this to special known cases in your own domains.
25122 .section "The SMTP-time rewriting flag" "SECTrewriteS"
25123 .cindex "SMTP" "rewriting malformed addresses"
25124 .cindex "RCPT" "rewriting argument of"
25125 .cindex "MAIL" "rewriting argument of"
25126 The rewrite flag &"S"& specifies a rewrite of incoming envelope addresses at
25127 SMTP time, as soon as an address is received in a MAIL or RCPT command, and
25128 before any other processing; even before syntax checking. The pattern is
25129 required to be a regular expression, and it is matched against the whole of the
25130 data for the command, including any surrounding angle brackets.
25132 .vindex "&$domain$&"
25133 .vindex "&$local_part$&"
25134 This form of rewrite rule allows for the handling of addresses that are not
25135 compliant with RFCs 2821 and 2822 (for example, &"bang paths"& in batched SMTP
25136 input). Because the input is not required to be a syntactically valid address,
25137 the variables &$local_part$& and &$domain$& are not available during the
25138 expansion of the replacement string. The result of rewriting replaces the
25139 original address in the MAIL or RCPT command.
25142 .section "Flags controlling the rewriting process" "SECID155"
25143 There are four flags which control the way the rewriting process works. These
25144 take effect only when a rule is invoked, that is, when the address is of the
25145 correct type (matches the flags) and matches the pattern:
25148 If the &"Q"& flag is set on a rule, the rewritten address is permitted to be an
25149 unqualified local part. It is qualified with &%qualify_recipient%&. In the
25150 absence of &"Q"& the rewritten address must always include a domain.
25152 If the &"q"& flag is set on a rule, no further rewriting rules are considered,
25153 even if no rewriting actually takes place because of a &"fail"& in the
25154 expansion. The &"q"& flag is not effective if the address is of the wrong type
25155 (does not match the flags) or does not match the pattern.
25157 The &"R"& flag causes a successful rewriting rule to be re-applied to the new
25158 address, up to ten times. It can be combined with the &"q"& flag, to stop
25159 rewriting once it fails to match (after at least one successful rewrite).
25161 .cindex "rewriting" "whole addresses"
25162 When an address in a header is rewritten, the rewriting normally applies only
25163 to the working part of the address, with any comments and RFC 2822 &"phrase"&
25164 left unchanged. For example, rewriting might change
25166 From: Ford Prefect <fp42@restaurant.hitch.fict.example>
25170 From: Ford Prefect <prefectf@hitch.fict.example>
25173 Sometimes there is a need to replace the whole address item, and this can be
25174 done by adding the flag letter &"w"& to a rule. If this is set on a rule that
25175 causes an address in a header line to be rewritten, the entire address is
25176 replaced, not just the working part. The replacement must be a complete RFC
25177 2822 address, including the angle brackets if necessary. If text outside angle
25178 brackets contains a character whose value is greater than 126 or less than 32
25179 (except for tab), the text is encoded according to RFC 2047. The character set
25180 is taken from &%headers_charset%&, which gets its default at build time.
25182 When the &"w"& flag is set on a rule that causes an envelope address to be
25183 rewritten, all but the working part of the replacement address is discarded.
25187 .section "Rewriting examples" "SECID156"
25188 Here is an example of the two common rewriting paradigms:
25190 *@*.hitch.fict.example $1@hitch.fict.example
25191 *@hitch.fict.example ${lookup{$1}dbm{/etc/realnames}\
25192 {$value}fail}@hitch.fict.example bctfrF
25194 Note the use of &"fail"& in the lookup expansion in the second rule, forcing
25195 the string expansion to fail if the lookup does not succeed. In this context it
25196 has the effect of leaving the original address unchanged, but Exim goes on to
25197 consider subsequent rewriting rules, if any, because the &"q"& flag is not
25198 present in that rule. An alternative to &"fail"& would be to supply &$1$&
25199 explicitly, which would cause the rewritten address to be the same as before,
25200 at the cost of a small bit of processing. Not supplying either of these is an
25201 error, since the rewritten address would then contain no local part.
25203 The first example above replaces the domain with a superior, more general
25204 domain. This may not be desirable for certain local parts. If the rule
25206 root@*.hitch.fict.example *
25208 were inserted before the first rule, rewriting would be suppressed for the
25209 local part &'root'& at any domain ending in &'hitch.fict.example'&.
25211 Rewriting can be made conditional on a number of tests, by making use of
25212 &${if$& in the expansion item. For example, to apply a rewriting rule only to
25213 messages that originate outside the local host:
25215 *@*.hitch.fict.example "${if !eq {$sender_host_address}{}\
25216 {$1@hitch.fict.example}fail}"
25218 The replacement string is quoted in this example because it contains white
25221 .cindex "rewriting" "bang paths"
25222 .cindex "bang paths" "rewriting"
25223 Exim does not handle addresses in the form of &"bang paths"&. If it sees such
25224 an address it treats it as an unqualified local part which it qualifies with
25225 the local qualification domain (if the source of the message is local or if the
25226 remote host is permitted to send unqualified addresses). Rewriting can
25227 sometimes be used to handle simple bang paths with a fixed number of
25228 components. For example, the rule
25230 \N^([^!]+)!(.*)@your.domain.example$\N $2@$1
25232 rewrites a two-component bang path &'host.name!user'& as the domain address
25233 &'user@host.name'&. However, there is a security implication in using this as
25234 a global rewriting rule for envelope addresses. It can provide a backdoor
25235 method for using your system as a relay, because the incoming addresses appear
25236 to be local. If the bang path addresses are received via SMTP, it is safer to
25237 use the &"S"& flag to rewrite them as they are received, so that relay checking
25238 can be done on the rewritten addresses.
25245 . ////////////////////////////////////////////////////////////////////////////
25246 . ////////////////////////////////////////////////////////////////////////////
25248 .chapter "Retry configuration" "CHAPretry"
25249 .scindex IIDretconf1 "retry" "configuration, description of"
25250 .scindex IIDregconf2 "configuration file" "retry section"
25251 The &"retry"& section of the runtime configuration file contains a list of
25252 retry rules that control how often Exim tries to deliver messages that cannot
25253 be delivered at the first attempt. If there are no retry rules (the section is
25254 empty or not present), there are no retries. In this situation, temporary
25255 errors are treated as permanent. The default configuration contains a single,
25256 general-purpose retry rule (see section &<<SECID57>>&). The &%-brt%& command
25257 line option can be used to test which retry rule will be used for a given
25258 address, domain and error.
25260 The most common cause of retries is temporary failure to deliver to a remote
25261 host because the host is down, or inaccessible because of a network problem.
25262 Exim's retry processing in this case is applied on a per-host (strictly, per IP
25263 address) basis, not on a per-message basis. Thus, if one message has recently
25264 been delayed, delivery of a new message to the same host is not immediately
25265 tried, but waits for the host's retry time to arrive. If the &%retry_defer%&
25266 log selector is set, the message
25267 .cindex "retry" "time not reached"
25268 &"retry time not reached"& is written to the main log whenever a delivery is
25269 skipped for this reason. Section &<<SECToutSMTPerr>>& contains more details of
25270 the handling of errors during remote deliveries.
25272 Retry processing applies to routing as well as to delivering, except as covered
25273 in the next paragraph. The retry rules do not distinguish between these
25274 actions. It is not possible, for example, to specify different behaviour for
25275 failures to route the domain &'snark.fict.example'& and failures to deliver to
25276 the host &'snark.fict.example'&. I didn't think anyone would ever need this
25277 added complication, so did not implement it. However, although they share the
25278 same retry rule, the actual retry times for routing and transporting a given
25279 domain are maintained independently.
25281 When a delivery is not part of a queue run (typically an immediate delivery on
25282 receipt of a message), the routers are always run, and local deliveries are
25283 always attempted, even if retry times are set for them. This makes for better
25284 behaviour if one particular message is causing problems (for example, causing
25285 quota overflow, or provoking an error in a filter file). If such a delivery
25286 suffers a temporary failure, the retry data is updated as normal, and
25287 subsequent delivery attempts from queue runs occur only when the retry time for
25288 the local address is reached.
25290 .section "Changing retry rules" "SECID157"
25291 If you change the retry rules in your configuration, you should consider
25292 whether or not to delete the retry data that is stored in Exim's spool area in
25293 files with names like &_db/retry_&. Deleting any of Exim's hints files is
25294 always safe; that is why they are called &"hints"&.
25296 The hints retry data contains suggested retry times based on the previous
25297 rules. In the case of a long-running problem with a remote host, it might
25298 record the fact that the host has timed out. If your new rules increase the
25299 timeout time for such a host, you should definitely remove the old retry data
25300 and let Exim recreate it, based on the new rules. Otherwise Exim might bounce
25301 messages that it should now be retaining.
25305 .section "Format of retry rules" "SECID158"
25306 .cindex "retry" "rules"
25307 Each retry rule occupies one line and consists of three or four parts,
25308 separated by white space: a pattern, an error name, an optional list of sender
25309 addresses, and a list of retry parameters. The pattern and sender lists must be
25310 enclosed in double quotes if they contain white space. The rules are searched
25311 in order until one is found where the pattern, error name, and sender list (if
25312 present) match the failing host or address, the error that occurred, and the
25313 message's sender, respectively.
25316 The pattern is any single item that may appear in an address list (see section
25317 &<<SECTaddresslist>>&). It is in fact processed as a one-item address list,
25318 which means that it is expanded before being tested against the address that
25319 has been delayed. A negated address list item is permitted. Address
25320 list processing treats a plain domain name as if it were preceded by &"*@"&,
25321 which makes it possible for many retry rules to start with just a domain. For
25324 lookingglass.fict.example * F,24h,30m;
25326 provides a rule for any address in the &'lookingglass.fict.example'& domain,
25329 alice@lookingglass.fict.example * F,24h,30m;
25331 applies only to temporary failures involving the local part &%alice%&.
25332 In practice, almost all rules start with a domain name pattern without a local
25335 .cindex "regular expressions" "in retry rules"
25336 &*Warning*&: If you use a regular expression in a retry rule pattern, it
25337 must match a complete address, not just a domain, because that is how regular
25338 expressions work in address lists.
25340 &`^\Nxyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Wrong%&
25341 &`^\N[^@]+@xyz\d+\.abc\.example$\N * G,1h,10m,2`& &%Right%&
25345 .section "Choosing which retry rule to use for address errors" "SECID159"
25346 When Exim is looking for a retry rule after a routing attempt has failed (for
25347 example, after a DNS timeout), each line in the retry configuration is tested
25348 against the complete address only if &%retry_use_local_part%& is set for the
25349 router. Otherwise, only the domain is used, except when matching against a
25350 regular expression, when the local part of the address is replaced with &"*"&.
25351 A domain on its own can match a domain pattern, or a pattern that starts with
25352 &"*@"&. By default, &%retry_use_local_part%& is true for routers where
25353 &%check_local_user%& is true, and false for other routers.
25355 Similarly, when Exim is looking for a retry rule after a local delivery has
25356 failed (for example, after a mailbox full error), each line in the retry
25357 configuration is tested against the complete address only if
25358 &%retry_use_local_part%& is set for the transport (it defaults true for all
25361 .cindex "4&'xx'& responses" "retry rules for"
25362 However, when Exim is looking for a retry rule after a remote delivery attempt
25363 suffers an address error (a 4&'xx'& SMTP response for a recipient address), the
25364 whole address is always used as the key when searching the retry rules. The
25365 rule that is found is used to create a retry time for the combination of the
25366 failing address and the message's sender. It is the combination of sender and
25367 recipient that is delayed in subsequent queue runs until its retry time is
25368 reached. You can delay the recipient without regard to the sender by setting
25369 &%address_retry_include_sender%& false in the &(smtp)& transport but this can
25370 lead to problems with servers that regularly issue 4&'xx'& responses to RCPT
25375 .section "Choosing which retry rule to use for host and message errors" &&&
25377 For a temporary error that is not related to an individual address (for
25378 example, a connection timeout), each line in the retry configuration is checked
25379 twice. First, the name of the remote host is used as a domain name (preceded by
25380 &"*@"& when matching a regular expression). If this does not match the line,
25381 the domain from the email address is tried in a similar fashion. For example,
25382 suppose the MX records for &'a.b.c.example'& are
25384 a.b.c.example MX 5 x.y.z.example
25388 and the retry rules are
25390 p.q.r.example * F,24h,30m;
25391 a.b.c.example * F,4d,45m;
25393 and a delivery to the host &'x.y.z.example'& suffers a connection failure. The
25394 first rule matches neither the host nor the domain, so Exim looks at the second
25395 rule. This does not match the host, but it does match the domain, so it is used
25396 to calculate the retry time for the host &'x.y.z.example'&. Meanwhile, Exim
25397 tries to deliver to &'p.q.r.example'&. If this also suffers a host error, the
25398 first retry rule is used, because it matches the host.
25400 In other words, temporary failures to deliver to host &'p.q.r.example'& use the
25401 first rule to determine retry times, but for all the other hosts for the domain
25402 &'a.b.c.example'&, the second rule is used. The second rule is also used if
25403 routing to &'a.b.c.example'& suffers a temporary failure.
25405 &*Note*&: The host name is used when matching the patterns, not its IP address.
25406 However, if a message is routed directly to an IP address without the use of a
25407 host name, for example, if a &(manualroute)& router contains a setting such as:
25409 route_list = *.a.example 192.168.34.23
25411 then the &"host name"& that is used when searching for a retry rule is the
25412 textual form of the IP address.
25414 .section "Retry rules for specific errors" "SECID161"
25415 .cindex "retry" "specific errors; specifying"
25416 The second field in a retry rule is the name of a particular error, or an
25417 asterisk, which matches any error. The errors that can be tested for are:
25420 .vitem &%auth_failed%&
25421 Authentication failed when trying to send to a host in the
25422 &%hosts_require_auth%& list in an &(smtp)& transport.
25424 .vitem &%data_4xx%&
25425 A 4&'xx'& error was received for an outgoing DATA command, either immediately
25426 after the command, or after sending the message's data.
25428 .vitem &%mail_4xx%&
25429 A 4&'xx'& error was received for an outgoing MAIL command.
25431 .vitem &%rcpt_4xx%&
25432 A 4&'xx'& error was received for an outgoing RCPT command.
25435 For the three 4&'xx'& errors, either the first or both of the x's can be given
25436 as specific digits, for example: &`mail_45x`& or &`rcpt_436`&. For example, to
25437 recognize 452 errors given to RCPT commands for addresses in a certain domain,
25438 and have retries every ten minutes with a one-hour timeout, you could set up a
25439 retry rule of this form:
25441 the.domain.name rcpt_452 F,1h,10m
25443 These errors apply to both outgoing SMTP (the &(smtp)& transport) and outgoing
25444 LMTP (either the &(lmtp)& transport, or the &(smtp)& transport in LMTP mode).
25447 .vitem &%lost_connection%&
25448 A server unexpectedly closed the SMTP connection. There may, of course,
25449 legitimate reasons for this (host died, network died), but if it repeats a lot
25450 for the same host, it indicates something odd.
25453 A DNS lookup for a host failed.
25454 Note that a &%dnslookup%& router will need to have matched
25455 its &%fail_defer_domains%& option for this retry type to be usable.
25456 Also note that a &%manualroute%& router will probably need
25457 its &%host_find_failed%& option set to &%defer%&.
25459 .vitem &%refused_MX%&
25460 A connection to a host obtained from an MX record was refused.
25462 .vitem &%refused_A%&
25463 A connection to a host not obtained from an MX record was refused.
25466 A connection was refused.
25468 .vitem &%timeout_connect_MX%&
25469 A connection attempt to a host obtained from an MX record timed out.
25471 .vitem &%timeout_connect_A%&
25472 A connection attempt to a host not obtained from an MX record timed out.
25474 .vitem &%timeout_connect%&
25475 A connection attempt timed out.
25477 .vitem &%timeout_MX%&
25478 There was a timeout while connecting or during an SMTP session with a host
25479 obtained from an MX record.
25481 .vitem &%timeout_A%&
25482 There was a timeout while connecting or during an SMTP session with a host not
25483 obtained from an MX record.
25486 There was a timeout while connecting or during an SMTP session.
25488 .vitem &%tls_required%&
25489 The server was required to use TLS (it matched &%hosts_require_tls%& in the
25490 &(smtp)& transport), but either did not offer TLS, or it responded with 4&'xx'&
25491 to STARTTLS, or there was a problem setting up the TLS connection.
25494 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
25497 .vitem &%quota_%&<&'time'&>
25498 .cindex "quota" "error testing in retry rule"
25499 .cindex "retry" "quota error testing"
25500 A mailbox quota was exceeded in a local delivery by the &(appendfile)&
25501 transport, and the mailbox has not been accessed for <&'time'&>. For example,
25502 &'quota_4d'& applies to a quota error when the mailbox has not been accessed
25506 .cindex "mailbox" "time of last read"
25507 The idea of &%quota_%&<&'time'&> is to make it possible to have shorter
25508 timeouts when the mailbox is full and is not being read by its owner. Ideally,
25509 it should be based on the last time that the user accessed the mailbox.
25510 However, it is not always possible to determine this. Exim uses the following
25514 If the mailbox is a single file, the time of last access (the &"atime"&) is
25515 used. As no new messages are being delivered (because the mailbox is over
25516 quota), Exim does not access the file, so this is the time of last user access.
25518 .cindex "maildir format" "time of last read"
25519 For a maildir delivery, the time of last modification of the &_new_&
25520 subdirectory is used. As the mailbox is over quota, no new files are created in
25521 the &_new_& subdirectory, because no new messages are being delivered. Any
25522 change to the &_new_& subdirectory is therefore assumed to be the result of an
25523 MUA moving a new message to the &_cur_& directory when it is first read. The
25524 time that is used is therefore the last time that the user read a new message.
25526 For other kinds of multi-file mailbox, the time of last access cannot be
25527 obtained, so a retry rule that uses this type of error field is never matched.
25530 The quota errors apply both to system-enforced quotas and to Exim's own quota
25531 mechanism in the &(appendfile)& transport. The &'quota'& error also applies
25532 when a local delivery is deferred because a partition is full (the ENOSPC
25537 .section "Retry rules for specified senders" "SECID162"
25538 .cindex "retry" "rules; sender-specific"
25539 You can specify retry rules that apply only when the failing message has a
25540 specific sender. In particular, this can be used to define retry rules that
25541 apply only to bounce messages. The third item in a retry rule can be of this
25544 &`senders=`&<&'address list'&>
25546 The retry timings themselves are then the fourth item. For example:
25548 * rcpt_4xx senders=: F,1h,30m
25550 matches recipient 4&'xx'& errors for bounce messages sent to any address at any
25551 host. If the address list contains white space, it must be enclosed in quotes.
25554 a.domain rcpt_452 senders="xb.dom : yc.dom" G,8h,10m,1.5
25556 &*Warning*&: This facility can be unhelpful if it is used for host errors
25557 (which do not depend on the recipient). The reason is that the sender is used
25558 only to match the retry rule. Once the rule has been found for a host error,
25559 its contents are used to set a retry time for the host, and this will apply to
25560 all messages, not just those with specific senders.
25562 When testing retry rules using &%-brt%&, you can supply a sender using the
25563 &%-f%& command line option, like this:
25565 exim -f "" -brt user@dom.ain
25567 If you do not set &%-f%& with &%-brt%&, a retry rule that contains a senders
25568 list is never matched.
25574 .section "Retry parameters" "SECID163"
25575 .cindex "retry" "parameters in rules"
25576 The third (or fourth, if a senders list is present) field in a retry rule is a
25577 sequence of retry parameter sets, separated by semicolons. Each set consists of
25579 <&'letter'&>,<&'cutoff time'&>,<&'arguments'&>
25581 The letter identifies the algorithm for computing a new retry time; the cutoff
25582 time is the time beyond which this algorithm no longer applies, and the
25583 arguments vary the algorithm's action. The cutoff time is measured from the
25584 time that the first failure for the domain (combined with the local part if
25585 relevant) was detected, not from the time the message was received.
25587 .cindex "retry" "algorithms"
25588 .cindex "retry" "fixed intervals"
25589 .cindex "retry" "increasing intervals"
25590 .cindex "retry" "random intervals"
25591 The available algorithms are:
25594 &'F'&: retry at fixed intervals. There is a single time parameter specifying
25597 &'G'&: retry at geometrically increasing intervals. The first argument
25598 specifies a starting value for the interval, and the second a multiplier, which
25599 is used to increase the size of the interval at each retry.
25601 &'H'&: retry at randomized intervals. The arguments are as for &'G'&. For each
25602 retry, the previous interval is multiplied by the factor in order to get a
25603 maximum for the next interval. The minimum interval is the first argument of
25604 the parameter, and an actual interval is chosen randomly between them. Such a
25605 rule has been found to be helpful in cluster configurations when all the
25606 members of the cluster restart at once, and may therefore synchronize their
25607 queue processing times.
25610 When computing the next retry time, the algorithm definitions are scanned in
25611 order until one whose cutoff time has not yet passed is reached. This is then
25612 used to compute a new retry time that is later than the current time. In the
25613 case of fixed interval retries, this simply means adding the interval to the
25614 current time. For geometrically increasing intervals, retry intervals are
25615 computed from the rule's parameters until one that is greater than the previous
25616 interval is found. The main configuration variable
25617 .cindex "limit" "retry interval"
25618 .cindex "retry" "interval, maximum"
25619 .oindex "&%retry_interval_max%&"
25620 &%retry_interval_max%& limits the maximum interval between retries. It
25621 cannot be set greater than &`24h`&, which is its default value.
25623 A single remote domain may have a number of hosts associated with it, and each
25624 host may have more than one IP address. Retry algorithms are selected on the
25625 basis of the domain name, but are applied to each IP address independently. If,
25626 for example, a host has two IP addresses and one is unusable, Exim will
25627 generate retry times for it and will not try to use it until its next retry
25628 time comes. Thus the good IP address is likely to be tried first most of the
25631 .cindex "hints database" "use for retrying"
25632 Retry times are hints rather than promises. Exim does not make any attempt to
25633 run deliveries exactly at the computed times. Instead, a queue runner process
25634 starts delivery processes for delayed messages periodically, and these attempt
25635 new deliveries only for those addresses that have passed their next retry time.
25636 If a new message arrives for a deferred address, an immediate delivery attempt
25637 occurs only if the address has passed its retry time. In the absence of new
25638 messages, the minimum time between retries is the interval between queue runner
25639 processes. There is not much point in setting retry times of five minutes if
25640 your queue runners happen only once an hour, unless there are a significant
25641 number of incoming messages (which might be the case on a system that is
25642 sending everything to a smart host, for example).
25644 The data in the retry hints database can be inspected by using the
25645 &'exim_dumpdb'& or &'exim_fixdb'& utility programs (see chapter
25646 &<<CHAPutils>>&). The latter utility can also be used to change the data. The
25647 &'exinext'& utility script can be used to find out what the next retry times
25648 are for the hosts associated with a particular mail domain, and also for local
25649 deliveries that have been deferred.
25652 .section "Retry rule examples" "SECID164"
25653 Here are some example retry rules:
25655 alice@wonderland.fict.example quota_5d F,7d,3h
25656 wonderland.fict.example quota_5d
25657 wonderland.fict.example * F,1h,15m; G,2d,1h,2;
25658 lookingglass.fict.example * F,24h,30m;
25659 * refused_A F,2h,20m;
25660 * * F,2h,15m; G,16h,1h,1.5; F,5d,8h
25662 The first rule sets up special handling for mail to
25663 &'alice@wonderland.fict.example'& when there is an over-quota error and the
25664 mailbox has not been read for at least 5 days. Retries continue every three
25665 hours for 7 days. The second rule handles over-quota errors for all other local
25666 parts at &'wonderland.fict.example'&; the absence of a local part has the same
25667 effect as supplying &"*@"&. As no retry algorithms are supplied, messages that
25668 fail are bounced immediately if the mailbox has not been read for at least 5
25671 The third rule handles all other errors at &'wonderland.fict.example'&; retries
25672 happen every 15 minutes for an hour, then with geometrically increasing
25673 intervals until two days have passed since a delivery first failed. After the
25674 first hour there is a delay of one hour, then two hours, then four hours, and
25675 so on (this is a rather extreme example).
25677 The fourth rule controls retries for the domain &'lookingglass.fict.example'&.
25678 They happen every 30 minutes for 24 hours only. The remaining two rules handle
25679 all other domains, with special action for connection refusal from hosts that
25680 were not obtained from an MX record.
25682 The final rule in a retry configuration should always have asterisks in the
25683 first two fields so as to provide a general catch-all for any addresses that do
25684 not have their own special handling. This example tries every 15 minutes for 2
25685 hours, then with intervals starting at one hour and increasing by a factor of
25686 1.5 up to 16 hours, then every 8 hours up to 5 days.
25690 .section "Timeout of retry data" "SECID165"
25691 .cindex "timeout" "of retry data"
25692 .oindex "&%retry_data_expire%&"
25693 .cindex "hints database" "data expiry"
25694 .cindex "retry" "timeout of data"
25695 Exim timestamps the data that it writes to its retry hints database. When it
25696 consults the data during a delivery it ignores any that is older than the value
25697 set in &%retry_data_expire%& (default 7 days). If, for example, a host hasn't
25698 been tried for 7 days, Exim will try to deliver to it immediately a message
25699 arrives, and if that fails, it will calculate a retry time as if it were
25700 failing for the first time.
25702 This improves the behaviour for messages routed to rarely-used hosts such as MX
25703 backups. If such a host was down at one time, and happens to be down again when
25704 Exim tries a month later, using the old retry data would imply that it had been
25705 down all the time, which is not a justified assumption.
25707 If a host really is permanently dead, this behaviour causes a burst of retries
25708 every now and again, but only if messages routed to it are rare. If there is a
25709 message at least once every 7 days the retry data never expires.
25714 .section "Long-term failures" "SECID166"
25715 .cindex "delivery failure, long-term"
25716 .cindex "retry" "after long-term failure"
25717 Special processing happens when an email address has been failing for so long
25718 that the cutoff time for the last algorithm is reached. For example, using the
25719 default retry rule:
25721 * * F,2h,15m; G,16h,1h,1.5; F,4d,6h
25723 the cutoff time is four days. Reaching the retry cutoff is independent of how
25724 long any specific message has been failing; it is the length of continuous
25725 failure for the recipient address that counts.
25727 When the cutoff time is reached for a local delivery, or for all the IP
25728 addresses associated with a remote delivery, a subsequent delivery failure
25729 causes Exim to give up on the address, and a bounce message is generated.
25730 In order to cater for new messages that use the failing address, a next retry
25731 time is still computed from the final algorithm, and is used as follows:
25733 For local deliveries, one delivery attempt is always made for any subsequent
25734 messages. If this delivery fails, the address fails immediately. The
25735 post-cutoff retry time is not used.
25737 If the delivery is remote, there are two possibilities, controlled by the
25738 .oindex "&%delay_after_cutoff%&"
25739 &%delay_after_cutoff%& option of the &(smtp)& transport. The option is true by
25740 default. Until the post-cutoff retry time for one of the IP addresses is
25741 reached, the failing email address is bounced immediately, without a delivery
25742 attempt taking place. After that time, one new delivery attempt is made to
25743 those IP addresses that are past their retry times, and if that still fails,
25744 the address is bounced and new retry times are computed.
25746 In other words, when all the hosts for a given email address have been failing
25747 for a long time, Exim bounces rather then defers until one of the hosts' retry
25748 times is reached. Then it tries once, and bounces if that attempt fails. This
25749 behaviour ensures that few resources are wasted in repeatedly trying to deliver
25750 to a broken destination, but if the host does recover, Exim will eventually
25753 If &%delay_after_cutoff%& is set false, Exim behaves differently. If all IP
25754 addresses are past their final cutoff time, Exim tries to deliver to those IP
25755 addresses that have not been tried since the message arrived. If there are
25756 no suitable IP addresses, or if they all fail, the address is bounced. In other
25757 words, it does not delay when a new message arrives, but tries the expired
25758 addresses immediately, unless they have been tried since the message arrived.
25759 If there is a continuous stream of messages for the failing domains, setting
25760 &%delay_after_cutoff%& false means that there will be many more attempts to
25761 deliver to permanently failing IP addresses than when &%delay_after_cutoff%& is
25764 .section "Deliveries that work intermittently" "SECID167"
25765 .cindex "retry" "intermittently working deliveries"
25766 Some additional logic is needed to cope with cases where a host is
25767 intermittently available, or when a message has some attribute that prevents
25768 its delivery when others to the same address get through. In this situation,
25769 because some messages are successfully delivered, the &"retry clock"& for the
25770 host or address keeps getting reset by the successful deliveries, and so
25771 failing messages remain on the queue for ever because the cutoff time is never
25774 Two exceptional actions are applied to prevent this happening. The first
25775 applies to errors that are related to a message rather than a remote host.
25776 Section &<<SECToutSMTPerr>>& has a discussion of the different kinds of error;
25777 examples of message-related errors are 4&'xx'& responses to MAIL or DATA
25778 commands, and quota failures. For this type of error, if a message's arrival
25779 time is earlier than the &"first failed"& time for the error, the earlier time
25780 is used when scanning the retry rules to decide when to try next and when to
25781 time out the address.
25783 The exceptional second action applies in all cases. If a message has been on
25784 the queue for longer than the cutoff time of any applicable retry rule for a
25785 given address, a delivery is attempted for that address, even if it is not yet
25786 time, and if this delivery fails, the address is timed out. A new retry time is
25787 not computed in this case, so that other messages for the same address are
25788 considered immediately.
25789 .ecindex IIDretconf1
25790 .ecindex IIDregconf2
25797 . ////////////////////////////////////////////////////////////////////////////
25798 . ////////////////////////////////////////////////////////////////////////////
25800 .chapter "SMTP authentication" "CHAPSMTPAUTH"
25801 .scindex IIDauthconf1 "SMTP" "authentication configuration"
25802 .scindex IIDauthconf2 "authentication"
25803 The &"authenticators"& section of Exim's run time configuration is concerned
25804 with SMTP authentication. This facility is an extension to the SMTP protocol,
25805 described in RFC 2554, which allows a client SMTP host to authenticate itself
25806 to a server. This is a common way for a server to recognize clients that are
25807 permitted to use it as a relay. SMTP authentication is not of relevance to the
25808 transfer of mail between servers that have no managerial connection with each
25811 .cindex "AUTH" "description of"
25812 Very briefly, the way SMTP authentication works is as follows:
25815 The server advertises a number of authentication &'mechanisms'& in response to
25816 the client's EHLO command.
25818 The client issues an AUTH command, naming a specific mechanism. The command
25819 may, optionally, contain some authentication data.
25821 The server may issue one or more &'challenges'&, to which the client must send
25822 appropriate responses. In simple authentication mechanisms, the challenges are
25823 just prompts for user names and passwords. The server does not have to issue
25824 any challenges &-- in some mechanisms the relevant data may all be transmitted
25825 with the AUTH command.
25827 The server either accepts or denies authentication.
25829 If authentication succeeds, the client may optionally make use of the AUTH
25830 option on the MAIL command to pass an authenticated sender in subsequent
25831 mail transactions. Authentication lasts for the remainder of the SMTP
25834 If authentication fails, the client may give up, or it may try a different
25835 authentication mechanism, or it may try transferring mail over the
25836 unauthenticated connection.
25839 If you are setting up a client, and want to know which authentication
25840 mechanisms the server supports, you can use Telnet to connect to port 25 (the
25841 SMTP port) on the server, and issue an EHLO command. The response to this
25842 includes the list of supported mechanisms. For example:
25844 &`$ `&&*&`telnet server.example 25`&*&
25845 &`Trying 192.168.34.25...`&
25846 &`Connected to server.example.`&
25847 &`Escape character is '^]'.`&
25848 &`220 server.example ESMTP Exim 4.20 ...`&
25849 &*&`ehlo client.example`&*&
25850 &`250-server.example Hello client.example [10.8.4.5]`&
25851 &`250-SIZE 52428800`&
25856 The second-last line of this example output shows that the server supports
25857 authentication using the PLAIN mechanism. In Exim, the different authentication
25858 mechanisms are configured by specifying &'authenticator'& drivers. Like the
25859 routers and transports, which authenticators are included in the binary is
25860 controlled by build-time definitions. The following are currently available,
25861 included by setting
25864 AUTH_CYRUS_SASL=yes
25867 AUTH_HEIMDAL_GSSAPI=yes
25872 in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5
25873 authentication mechanism (RFC 2195), and the second provides an interface to
25874 the Cyrus SASL authentication library.
25875 The third is an interface to Dovecot's authentication system, delegating the
25876 work via a socket interface.
25877 The fourth provides an interface to the GNU SASL authentication library, which
25878 provides mechanisms but typically not data sources.
25879 The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but
25880 supporting setting a server keytab.
25881 The sixth can be configured to support
25882 the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is
25883 not formally documented, but used by several MUAs. The seventh authenticator
25884 supports Microsoft's &'Secure Password Authentication'& mechanism.
25885 The eighth is an Exim authenticator but not an SMTP one;
25886 instead it can use information from a TLS negotiation.
25888 The authenticators are configured using the same syntax as other drivers (see
25889 section &<<SECTfordricon>>&). If no authenticators are required, no
25890 authentication section need be present in the configuration file. Each
25891 authenticator can in principle have both server and client functions. When Exim
25892 is receiving SMTP mail, it is acting as a server; when it is sending out
25893 messages over SMTP, it is acting as a client. Authenticator configuration
25894 options are provided for use in both these circumstances.
25896 To make it clear which options apply to which situation, the prefixes
25897 &%server_%& and &%client_%& are used on option names that are specific to
25898 either the server or the client function, respectively. Server and client
25899 functions are disabled if none of their options are set. If an authenticator is
25900 to be used for both server and client functions, a single definition, using
25901 both sets of options, is required. For example:
25905 public_name = CRAM-MD5
25906 server_secret = ${if eq{$auth1}{ph10}{secret1}fail}
25908 client_secret = secret2
25910 The &%server_%& option is used when Exim is acting as a server, and the
25911 &%client_%& options when it is acting as a client.
25913 Descriptions of the individual authenticators are given in subsequent chapters.
25914 The remainder of this chapter covers the generic options for the
25915 authenticators, followed by general discussion of the way authentication works
25918 &*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and
25919 per-mechanism basis. Please read carefully to determine which variables hold
25920 account labels such as usercodes and which hold passwords or other
25921 authenticating data.
25923 Note that some mechanisms support two different identifiers for accounts: the
25924 &'authentication id'& and the &'authorization id'&. The contractions &'authn'&
25925 and &'authz'& are commonly encountered. The American spelling is standard here.
25926 Conceptually, authentication data such as passwords are tied to the identifier
25927 used to authenticate; servers may have rules to permit one user to act as a
25928 second user, so that after login the session is treated as though that second
25929 user had logged in. That second user is the &'authorization id'&. A robust
25930 configuration might confirm that the &'authz'& field is empty or matches the
25931 &'authn'& field. Often this is just ignored. The &'authn'& can be considered
25932 as verified data, the &'authz'& as an unverified request which the server might
25935 A &'realm'& is a text string, typically a domain name, presented by a server
25936 to a client to help it select an account and credentials to use. In some
25937 mechanisms, the client and server provably agree on the realm, but clients
25938 typically can not treat the realm as secure data to be blindly trusted.
25942 .section "Generic options for authenticators" "SECID168"
25943 .cindex "authentication" "generic options"
25944 .cindex "options" "generic; for authenticators"
25946 .option client_condition authenticators string&!! unset
25947 When Exim is authenticating as a client, it skips any authenticator whose
25948 &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be
25949 used, for example, to skip plain text authenticators when the connection is not
25950 encrypted by a setting such as:
25952 client_condition = ${if !eq{$tls_out_cipher}{}}
25956 .option client_set_id authenticators string&!! unset
25957 When client authentication succeeds, this condition is expanded; the
25958 result is used in the log lines for outbound messages.
25959 Typically it will be the user name used for authentication.
25962 .option driver authenticators string unset
25963 This option must always be set. It specifies which of the available
25964 authenticators is to be used.
25967 .option public_name authenticators string unset
25968 This option specifies the name of the authentication mechanism that the driver
25969 implements, and by which it is known to the outside world. These names should
25970 contain only upper case letters, digits, underscores, and hyphens (RFC 2222),
25971 but Exim in fact matches them caselessly. If &%public_name%& is not set, it
25972 defaults to the driver's instance name.
25975 .option server_advertise_condition authenticators string&!! unset
25976 When a server is about to advertise an authentication mechanism, the condition
25977 is expanded. If it yields the empty string, &"0"&, &"no"&, or &"false"&, the
25978 mechanism is not advertised.
25979 If the expansion fails, the mechanism is not advertised. If the failure was not
25980 forced, and was not caused by a lookup defer, the incident is logged.
25981 See section &<<SECTauthexiser>>& below for further discussion.
25984 .option server_condition authenticators string&!! unset
25985 This option must be set for a &%plaintext%& server authenticator, where it
25986 is used directly to control authentication. See section &<<SECTplainserver>>&
25989 For the &(gsasl)& authenticator, this option is required for various
25990 mechanisms; see chapter &<<CHAPgsasl>>& for details.
25992 For the other authenticators, &%server_condition%& can be used as an additional
25993 authentication or authorization mechanism that is applied after the other
25994 authenticator conditions succeed. If it is set, it is expanded when the
25995 authenticator would otherwise return a success code. If the expansion is forced
25996 to fail, authentication fails. Any other expansion failure causes a temporary
25997 error code to be returned. If the result of a successful expansion is an empty
25998 string, &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
25999 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds. For any
26000 other result, a temporary error code is returned, with the expanded string as
26004 .option server_debug_print authenticators string&!! unset
26005 If this option is set and authentication debugging is enabled (see the &%-d%&
26006 command line option), the string is expanded and included in the debugging
26007 output when the authenticator is run as a server. This can help with checking
26008 out the values of variables.
26009 If expansion of the string fails, the error message is written to the debugging
26010 output, and Exim carries on processing.
26013 .option server_set_id authenticators string&!! unset
26014 .vindex "&$authenticated_id$&"
26015 When an Exim server successfully authenticates a client, this string is
26016 expanded using data from the authentication, and preserved for any incoming
26017 messages in the variable &$authenticated_id$&. It is also included in the log
26018 lines for incoming messages. For example, a user/password authenticator
26019 configuration might preserve the user name that was used to authenticate, and
26020 refer to it subsequently during delivery of the message.
26021 If expansion fails, the option is ignored.
26024 .option server_mail_auth_condition authenticators string&!! unset
26025 This option allows a server to discard authenticated sender addresses supplied
26026 as part of MAIL commands in SMTP connections that are authenticated by the
26027 driver on which &%server_mail_auth_condition%& is set. The option is not used
26028 as part of the authentication process; instead its (unexpanded) value is
26029 remembered for later use.
26030 How it is used is described in the following section.
26036 .section "The AUTH parameter on MAIL commands" "SECTauthparamail"
26037 .cindex "authentication" "sender; authenticated"
26038 .cindex "AUTH" "on MAIL command"
26039 When a client supplied an AUTH= item on a MAIL command, Exim applies
26040 the following checks before accepting it as the authenticated sender of the
26044 If the connection is not using extended SMTP (that is, HELO was used rather
26045 than EHLO), the use of AUTH= is a syntax error.
26047 If the value of the AUTH= parameter is &"<>"&, it is ignored.
26049 .vindex "&$authenticated_sender$&"
26050 If &%acl_smtp_mailauth%& is defined, the ACL it specifies is run. While it is
26051 running, the value of &$authenticated_sender$& is set to the value obtained
26052 from the AUTH= parameter. If the ACL does not yield &"accept"&, the value of
26053 &$authenticated_sender$& is deleted. The &%acl_smtp_mailauth%& ACL may not
26054 return &"drop"& or &"discard"&. If it defers, a temporary error code (451) is
26055 given for the MAIL command.
26057 If &%acl_smtp_mailauth%& is not defined, the value of the AUTH= parameter
26058 is accepted and placed in &$authenticated_sender$& only if the client has
26061 If the AUTH= value was accepted by either of the two previous rules, and
26062 the client has authenticated, and the authenticator has a setting for the
26063 &%server_mail_auth_condition%&, the condition is checked at this point. The
26064 valued that was saved from the authenticator is expanded. If the expansion
26065 fails, or yields an empty string, &"0"&, &"no"&, or &"false"&, the value of
26066 &$authenticated_sender$& is deleted. If the expansion yields any other value,
26067 the value of &$authenticated_sender$& is retained and passed on with the
26072 When &$authenticated_sender$& is set for a message, it is passed on to other
26073 hosts to which Exim authenticates as a client. Do not confuse this value with
26074 &$authenticated_id$&, which is a string obtained from the authentication
26075 process, and which is not usually a complete email address.
26077 .vindex "&$sender_address$&"
26078 Whenever an AUTH= value is ignored, the incident is logged. The ACL for
26079 MAIL, if defined, is run after AUTH= is accepted or ignored. It can
26080 therefore make use of &$authenticated_sender$&. The converse is not true: the
26081 value of &$sender_address$& is not yet set up when the &%acl_smtp_mailauth%&
26086 .section "Authentication on an Exim server" "SECTauthexiser"
26087 .cindex "authentication" "on an Exim server"
26088 When Exim receives an EHLO command, it advertises the public names of those
26089 authenticators that are configured as servers, subject to the following
26093 The client host must match &%auth_advertise_hosts%& (default *).
26095 It the &%server_advertise_condition%& option is set, its expansion must not
26096 yield the empty string, &"0"&, &"no"&, or &"false"&.
26099 The order in which the authenticators are defined controls the order in which
26100 the mechanisms are advertised.
26102 Some mail clients (for example, some versions of Netscape) require the user to
26103 provide a name and password for authentication whenever AUTH is advertised,
26104 even though authentication may not in fact be needed (for example, Exim may be
26105 set up to allow unconditional relaying from the client by an IP address check).
26106 You can make such clients more friendly by not advertising AUTH to them.
26107 For example, if clients on the 10.9.8.0/24 network are permitted (by the ACL
26108 that runs for RCPT) to relay without authentication, you should set
26110 auth_advertise_hosts = ! 10.9.8.0/24
26112 so that no authentication mechanisms are advertised to them.
26114 The &%server_advertise_condition%& controls the advertisement of individual
26115 authentication mechanisms. For example, it can be used to restrict the
26116 advertisement of a particular mechanism to encrypted connections, by a setting
26119 server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}}
26121 .vindex "&$tls_in_cipher$&"
26122 If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion
26123 yields &"yes"&, which allows the advertisement to happen.
26125 When an Exim server receives an AUTH command from a client, it rejects it
26126 immediately if AUTH was not advertised in response to an earlier EHLO
26127 command. This is the case if
26130 The client host does not match &%auth_advertise_hosts%&; or
26132 No authenticators are configured with server options; or
26134 Expansion of &%server_advertise_condition%& blocked the advertising of all the
26135 server authenticators.
26139 Otherwise, Exim runs the ACL specified by &%acl_smtp_auth%& in order
26140 to decide whether to accept the command. If &%acl_smtp_auth%& is not set,
26141 AUTH is accepted from any client host.
26143 If AUTH is not rejected by the ACL, Exim searches its configuration for a
26144 server authentication mechanism that was advertised in response to EHLO and
26145 that matches the one named in the AUTH command. If it finds one, it runs
26146 the appropriate authentication protocol, and authentication either succeeds or
26147 fails. If there is no matching advertised mechanism, the AUTH command is
26148 rejected with a 504 error.
26150 .vindex "&$received_protocol$&"
26151 .vindex "&$sender_host_authenticated$&"
26152 When a message is received from an authenticated host, the value of
26153 &$received_protocol$& is set to &"esmtpa"& or &"esmtpsa"& instead of &"esmtp"&
26154 or &"esmtps"&, and &$sender_host_authenticated$& contains the name (not the
26155 public name) of the authenticator driver that successfully authenticated the
26156 client from which the message was received. This variable is empty if there was
26157 no successful authentication.
26159 .cindex authentication "expansion item"
26160 Successful authentication sets up information used by the
26161 &$authresults$& expansion item.
26166 .section "Testing server authentication" "SECID169"
26167 .cindex "authentication" "testing a server"
26168 .cindex "AUTH" "testing a server"
26169 .cindex "base64 encoding" "creating authentication test data"
26170 Exim's &%-bh%& option can be useful for testing server authentication
26171 configurations. The data for the AUTH command has to be sent using base64
26172 encoding. A quick way to produce such data for testing is the following Perl
26176 printf ("%s", encode_base64(eval "\"$ARGV[0]\""));
26178 .cindex "binary zero" "in authentication data"
26179 This interprets its argument as a Perl string, and then encodes it. The
26180 interpretation as a Perl string allows binary zeros, which are required for
26181 some kinds of authentication, to be included in the data. For example, a
26182 command line to run this script on such data might be
26184 encode '\0user\0password'
26186 Note the use of single quotes to prevent the shell interpreting the
26187 backslashes, so that they can be interpreted by Perl to specify characters
26188 whose code value is zero.
26190 &*Warning 1*&: If either of the user or password strings starts with an octal
26191 digit, you must use three zeros instead of one after the leading backslash. If
26192 you do not, the octal digit that starts your string will be incorrectly
26193 interpreted as part of the code for the first character.
26195 &*Warning 2*&: If there are characters in the strings that Perl interprets
26196 specially, you must use a Perl escape to prevent them being misinterpreted. For
26197 example, a command such as
26199 encode '\0user@domain.com\0pas$$word'
26201 gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
26203 If you have the &%mimencode%& command installed, another way to do produce
26204 base64-encoded strings is to run the command
26206 echo -e -n `\0user\0password' | mimencode
26208 The &%-e%& option of &%echo%& enables the interpretation of backslash escapes
26209 in the argument, and the &%-n%& option specifies no newline at the end of its
26210 output. However, not all versions of &%echo%& recognize these options, so you
26211 should check your version before relying on this suggestion.
26215 .section "Authentication by an Exim client" "SECID170"
26216 .cindex "authentication" "on an Exim client"
26217 The &(smtp)& transport has two options called &%hosts_require_auth%& and
26218 &%hosts_try_auth%&. When the &(smtp)& transport connects to a server that
26219 announces support for authentication, and the host matches an entry in either
26220 of these options, Exim (as a client) tries to authenticate as follows:
26223 For each authenticator that is configured as a client, in the order in which
26224 they are defined in the configuration, it searches the authentication
26225 mechanisms announced by the server for one whose name matches the public name
26226 of the authenticator.
26229 .vindex "&$host_address$&"
26230 When it finds one that matches, it runs the authenticator's client code. The
26231 variables &$host$& and &$host_address$& are available for any string expansions
26232 that the client might do. They are set to the server's name and IP address. If
26233 any expansion is forced to fail, the authentication attempt is abandoned, and
26234 Exim moves on to the next authenticator. Otherwise an expansion failure causes
26235 delivery to be deferred.
26237 If the result of the authentication attempt is a temporary error or a timeout,
26238 Exim abandons trying to send the message to the host for the moment. It will
26239 try again later. If there are any backup hosts available, they are tried in the
26242 If the response to authentication is a permanent error (5&'xx'& code), Exim
26243 carries on searching the list of authenticators and tries another one if
26244 possible. If all authentication attempts give permanent errors, or if there are
26245 no attempts because no mechanisms match (or option expansions force failure),
26246 what happens depends on whether the host matches &%hosts_require_auth%& or
26247 &%hosts_try_auth%&. In the first case, a temporary error is generated, and
26248 delivery is deferred. The error can be detected in the retry rules, and thereby
26249 turned into a permanent error if you wish. In the second case, Exim tries to
26250 deliver the message unauthenticated.
26253 Note that the hostlist test for whether to do authentication can be
26254 confused if name-IP lookups change between the time the peer is decided
26255 upon and the time that the transport runs. For example, with a manualroute
26256 router given a host name, and with DNS "round-robin" used by that name: if
26257 the local resolver cache times out between the router and the transport
26258 running, the transport may get an IP for the name for its authentication
26259 check which does not match the connection peer IP.
26260 No authentication will then be done, despite the names being identical.
26262 For such cases use a separate transport which always authenticates.
26264 .cindex "AUTH" "on MAIL command"
26265 When Exim has authenticated itself to a remote server, it adds the AUTH
26266 parameter to the MAIL commands it sends, if it has an authenticated sender for
26267 the message. If the message came from a remote host, the authenticated sender
26268 is the one that was receiving on an incoming MAIL command, provided that the
26269 incoming connection was authenticated and the &%server_mail_auth%& condition
26270 allowed the authenticated sender to be retained. If a local process calls Exim
26271 to send a message, the sender address that is built from the login name and
26272 &%qualify_domain%& is treated as authenticated. However, if the
26273 &%authenticated_sender%& option is set on the &(smtp)& transport, it overrides
26274 the authenticated sender that was received with the message.
26275 .ecindex IIDauthconf1
26276 .ecindex IIDauthconf2
26283 . ////////////////////////////////////////////////////////////////////////////
26284 . ////////////////////////////////////////////////////////////////////////////
26286 .chapter "The plaintext authenticator" "CHAPplaintext"
26287 .scindex IIDplaiauth1 "&(plaintext)& authenticator"
26288 .scindex IIDplaiauth2 "authenticators" "&(plaintext)&"
26289 The &(plaintext)& authenticator can be configured to support the PLAIN and
26290 LOGIN authentication mechanisms, both of which transfer authentication data as
26291 plain (unencrypted) text (though base64 encoded). The use of plain text is a
26292 security risk; you are strongly advised to insist on the use of SMTP encryption
26293 (see chapter &<<CHAPTLS>>&) if you use the PLAIN or LOGIN mechanisms. If you do
26294 use unencrypted plain text, you should not use the same passwords for SMTP
26295 connections as you do for login accounts.
26297 .section "Plaintext options" "SECID171"
26298 .cindex "options" "&(plaintext)& authenticator (server)"
26299 When configured as a server, &(plaintext)& uses the following options:
26301 .option server_condition authenticators string&!! unset
26302 This is actually a global authentication option, but it must be set in order to
26303 configure the &(plaintext)& driver as a server. Its use is described below.
26305 .option server_prompts plaintext string&!! unset
26306 The contents of this option, after expansion, must be a colon-separated list of
26307 prompt strings. If expansion fails, a temporary authentication rejection is
26310 .section "Using plaintext in a server" "SECTplainserver"
26311 .cindex "AUTH" "in &(plaintext)& authenticator"
26312 .cindex "binary zero" "in &(plaintext)& authenticator"
26313 .cindex "numerical variables (&$1$& &$2$& etc)" &&&
26314 "in &(plaintext)& authenticator"
26315 .vindex "&$auth1$&, &$auth2$&, etc"
26316 .cindex "base64 encoding" "in &(plaintext)& authenticator"
26318 When running as a server, &(plaintext)& performs the authentication test by
26319 expanding a string. The data sent by the client with the AUTH command, or in
26320 response to subsequent prompts, is base64 encoded, and so may contain any byte
26321 values when decoded. If any data is supplied with the command, it is treated as
26322 a list of strings, separated by NULs (binary zeros), the first three of which
26323 are placed in the expansion variables &$auth1$&, &$auth2$&, and &$auth3$&
26324 (neither LOGIN nor PLAIN uses more than three strings).
26326 For compatibility with previous releases of Exim, the values are also placed in
26327 the expansion variables &$1$&, &$2$&, and &$3$&. However, the use of these
26328 variables for this purpose is now deprecated, as it can lead to confusion in
26329 string expansions that also use them for other things.
26331 If there are more strings in &%server_prompts%& than the number of strings
26332 supplied with the AUTH command, the remaining prompts are used to obtain more
26333 data. Each response from the client may be a list of NUL-separated strings.
26335 .vindex "&$authenticated_id$&"
26336 Once a sufficient number of data strings have been received,
26337 &%server_condition%& is expanded. If the expansion is forced to fail,
26338 authentication fails. Any other expansion failure causes a temporary error code
26339 to be returned. If the result of a successful expansion is an empty string,
26340 &"0"&, &"no"&, or &"false"&, authentication fails. If the result of the
26341 expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the
26342 generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&.
26343 For any other result, a temporary error code is returned, with the expanded
26344 string as the error text
26346 &*Warning*&: If you use a lookup in the expansion to find the user's
26347 password, be sure to make the authentication fail if the user is unknown.
26348 There are good and bad examples at the end of the next section.
26352 .section "The PLAIN authentication mechanism" "SECID172"
26353 .cindex "PLAIN authentication mechanism"
26354 .cindex "authentication" "PLAIN mechanism"
26355 .cindex "binary zero" "in &(plaintext)& authenticator"
26356 The PLAIN authentication mechanism (RFC 2595) specifies that three strings be
26357 sent as one item of data (that is, one combined string containing two NUL
26358 separators). The data is sent either as part of the AUTH command, or
26359 subsequently in response to an empty prompt from the server.
26361 The second and third strings are a user name and a corresponding password.
26362 Using a single fixed user name and password as an example, this could be
26363 configured as follows:
26367 public_name = PLAIN
26369 server_condition = \
26370 ${if and {{eq{$auth2}{username}}{eq{$auth3}{mysecret}}}}
26371 server_set_id = $auth2
26373 Note that the default result strings from &%if%& (&"true"& or an empty string)
26374 are exactly what we want here, so they need not be specified. Obviously, if the
26375 password contains expansion-significant characters such as dollar, backslash,
26376 or closing brace, they have to be escaped.
26378 The &%server_prompts%& setting specifies a single, empty prompt (empty items at
26379 the end of a string list are ignored). If all the data comes as part of the
26380 AUTH command, as is commonly the case, the prompt is not used. This
26381 authenticator is advertised in the response to EHLO as
26385 and a client host can authenticate itself by sending the command
26387 AUTH PLAIN AHVzZXJuYW1lAG15c2VjcmV0
26389 As this contains three strings (more than the number of prompts), no further
26390 data is required from the client. Alternatively, the client may just send
26394 to initiate authentication, in which case the server replies with an empty
26395 prompt. The client must respond with the combined data string.
26397 The data string is base64 encoded, as required by the RFC. This example,
26398 when decoded, is <&'NUL'&>&`username`&<&'NUL'&>&`mysecret`&, where <&'NUL'&>
26399 represents a zero byte. This is split up into three strings, the first of which
26400 is empty. The &%server_condition%& option in the authenticator checks that the
26401 second two are &`username`& and &`mysecret`& respectively.
26403 Having just one fixed user name and password, as in this example, is not very
26404 realistic, though for a small organization with only a handful of
26405 authenticating clients it could make sense.
26407 A more sophisticated instance of this authenticator could use the user name in
26408 &$auth2$& to look up a password in a file or database, and maybe do an encrypted
26409 comparison (see &%crypteq%& in chapter &<<CHAPexpand>>&). Here is a example of
26410 this approach, where the passwords are looked up in a DBM file. &*Warning*&:
26411 This is an incorrect example:
26413 server_condition = \
26414 ${if eq{$auth3}{${lookup{$auth2}dbm{/etc/authpwd}}}}
26416 The expansion uses the user name (&$auth2$&) as the key to look up a password,
26417 which it then compares to the supplied password (&$auth3$&). Why is this example
26418 incorrect? It works fine for existing users, but consider what happens if a
26419 non-existent user name is given. The lookup fails, but as no success/failure
26420 strings are given for the lookup, it yields an empty string. Thus, to defeat
26421 the authentication, all a client has to do is to supply a non-existent user
26422 name and an empty password. The correct way of writing this test is:
26424 server_condition = ${lookup{$auth2}dbm{/etc/authpwd}\
26425 {${if eq{$value}{$auth3}}} {false}}
26427 In this case, if the lookup succeeds, the result is checked; if the lookup
26428 fails, &"false"& is returned and authentication fails. If &%crypteq%& is being
26429 used instead of &%eq%&, the first example is in fact safe, because &%crypteq%&
26430 always fails if its second argument is empty. However, the second way of
26431 writing the test makes the logic clearer.
26434 .section "The LOGIN authentication mechanism" "SECID173"
26435 .cindex "LOGIN authentication mechanism"
26436 .cindex "authentication" "LOGIN mechanism"
26437 The LOGIN authentication mechanism is not documented in any RFC, but is in use
26438 in a number of programs. No data is sent with the AUTH command. Instead, a
26439 user name and password are supplied separately, in response to prompts. The
26440 plaintext authenticator can be configured to support this as in this example:
26444 public_name = LOGIN
26445 server_prompts = User Name : Password
26446 server_condition = \
26447 ${if and {{eq{$auth1}{username}}{eq{$auth2}{mysecret}}}}
26448 server_set_id = $auth1
26450 Because of the way plaintext operates, this authenticator accepts data supplied
26451 with the AUTH command (in contravention of the specification of LOGIN), but
26452 if the client does not supply it (as is the case for LOGIN clients), the prompt
26453 strings are used to obtain two data items.
26455 Some clients are very particular about the precise text of the prompts. For
26456 example, Outlook Express is reported to recognize only &"Username:"& and
26457 &"Password:"&. Here is an example of a LOGIN authenticator that uses those
26458 strings. It uses the &%ldapauth%& expansion condition to check the user
26459 name and password by binding to an LDAP server:
26463 public_name = LOGIN
26464 server_prompts = Username:: : Password::
26465 server_condition = ${if and{{ \
26468 user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \
26469 pass=${quote:$auth2} \
26470 ldap://ldap.example.org/} }} }
26471 server_set_id = uid=$auth1,ou=people,o=example.org
26473 We have to check that the username is not empty before using it, because LDAP
26474 does not permit empty DN components. We must also use the &%quote_ldap_dn%&
26475 operator to correctly quote the DN for authentication. However, the basic
26476 &%quote%& operator, rather than any of the LDAP quoting operators, is the
26477 correct one to use for the password, because quoting is needed only to make
26478 the password conform to the Exim syntax. At the LDAP level, the password is an
26479 uninterpreted string.
26482 .section "Support for different kinds of authentication" "SECID174"
26483 A number of string expansion features are provided for the purpose of
26484 interfacing to different ways of user authentication. These include checking
26485 traditionally encrypted passwords from &_/etc/passwd_& (or equivalent), PAM,
26486 Radius, &%ldapauth%&, &'pwcheck'&, and &'saslauthd'&. For details see section
26492 .section "Using plaintext in a client" "SECID175"
26493 .cindex "options" "&(plaintext)& authenticator (client)"
26494 The &(plaintext)& authenticator has two client options:
26496 .option client_ignore_invalid_base64 plaintext boolean false
26497 If the client receives a server prompt that is not a valid base64 string,
26498 authentication is abandoned by default. However, if this option is set true,
26499 the error in the challenge is ignored and the client sends the response as
26502 .option client_send plaintext string&!! unset
26503 The string is a colon-separated list of authentication data strings. Each
26504 string is independently expanded before being sent to the server. The first
26505 string is sent with the AUTH command; any more strings are sent in response
26506 to prompts from the server. Before each string is expanded, the value of the
26507 most recent prompt is placed in the next &$auth$&<&'n'&> variable, starting
26508 with &$auth1$& for the first prompt. Up to three prompts are stored in this
26509 way. Thus, the prompt that is received in response to sending the first string
26510 (with the AUTH command) can be used in the expansion of the second string, and
26511 so on. If an invalid base64 string is received when
26512 &%client_ignore_invalid_base64%& is set, an empty string is put in the
26513 &$auth$&<&'n'&> variable.
26515 &*Note*&: You cannot use expansion to create multiple strings, because
26516 splitting takes priority and happens first.
26518 Because the PLAIN authentication mechanism requires NUL (binary zero) bytes in
26519 the data, further processing is applied to each string before it is sent. If
26520 there are any single circumflex characters in the string, they are converted to
26521 NULs. Should an actual circumflex be required as data, it must be doubled in
26524 This is an example of a client configuration that implements the PLAIN
26525 authentication mechanism with a fixed user name and password:
26529 public_name = PLAIN
26530 client_send = ^username^mysecret
26532 The lack of colons means that the entire text is sent with the AUTH
26533 command, with the circumflex characters converted to NULs. A similar example
26534 that uses the LOGIN mechanism is:
26538 public_name = LOGIN
26539 client_send = : username : mysecret
26541 The initial colon means that the first string is empty, so no data is sent with
26542 the AUTH command itself. The remaining strings are sent in response to
26544 .ecindex IIDplaiauth1
26545 .ecindex IIDplaiauth2
26550 . ////////////////////////////////////////////////////////////////////////////
26551 . ////////////////////////////////////////////////////////////////////////////
26553 .chapter "The cram_md5 authenticator" "CHID9"
26554 .scindex IIDcramauth1 "&(cram_md5)& authenticator"
26555 .scindex IIDcramauth2 "authenticators" "&(cram_md5)&"
26556 .cindex "CRAM-MD5 authentication mechanism"
26557 .cindex "authentication" "CRAM-MD5 mechanism"
26558 The CRAM-MD5 authentication mechanism is described in RFC 2195. The server
26559 sends a challenge string to the client, and the response consists of a user
26560 name and the CRAM-MD5 digest of the challenge string combined with a secret
26561 string (password) which is known to both server and client. Thus, the secret
26562 is not sent over the network as plain text, which makes this authenticator more
26563 secure than &(plaintext)&. However, the downside is that the secret has to be
26564 available in plain text at either end.
26567 .section "Using cram_md5 as a server" "SECID176"
26568 .cindex "options" "&(cram_md5)& authenticator (server)"
26569 This authenticator has one server option, which must be set to configure the
26570 authenticator as a server:
26572 .option server_secret cram_md5 string&!! unset
26573 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(cram_md5)& authenticator"
26574 When the server receives the client's response, the user name is placed in
26575 the expansion variable &$auth1$&, and &%server_secret%& is expanded to
26576 obtain the password for that user. The server then computes the CRAM-MD5 digest
26577 that the client should have sent, and checks that it received the correct
26578 string. If the expansion of &%server_secret%& is forced to fail, authentication
26579 fails. If the expansion fails for some other reason, a temporary error code is
26580 returned to the client.
26582 For compatibility with previous releases of Exim, the user name is also placed
26583 in &$1$&. However, the use of this variables for this purpose is now
26584 deprecated, as it can lead to confusion in string expansions that also use
26585 numeric variables for other things.
26587 For example, the following authenticator checks that the user name given by the
26588 client is &"ph10"&, and if so, uses &"secret"& as the password. For any other
26589 user name, authentication fails.
26593 public_name = CRAM-MD5
26594 server_secret = ${if eq{$auth1}{ph10}{secret}fail}
26595 server_set_id = $auth1
26597 .vindex "&$authenticated_id$&"
26598 If authentication succeeds, the setting of &%server_set_id%& preserves the user
26599 name in &$authenticated_id$&. A more typical configuration might look up the
26600 secret string in a file, using the user name as the key. For example:
26604 public_name = CRAM-MD5
26605 server_secret = ${lookup{$auth1}lsearch{/etc/authpwd}\
26607 server_set_id = $auth1
26609 Note that this expansion explicitly forces failure if the lookup fails
26610 because &$auth1$& contains an unknown user name.
26612 As another example, if you wish to re-use a Cyrus SASL sasldb2 file without
26613 using the relevant libraries, you need to know the realm to specify in the
26614 lookup and then ask for the &"userPassword"& attribute for that user in that
26619 public_name = CRAM-MD5
26620 server_secret = ${lookup{$auth1:mail.example.org:userPassword}\
26621 dbmjz{/etc/sasldb2}{$value}fail}
26622 server_set_id = $auth1
26625 .section "Using cram_md5 as a client" "SECID177"
26626 .cindex "options" "&(cram_md5)& authenticator (client)"
26627 When used as a client, the &(cram_md5)& authenticator has two options:
26631 .option client_name cram_md5 string&!! "the primary host name"
26632 This string is expanded, and the result used as the user name data when
26633 computing the response to the server's challenge.
26636 .option client_secret cram_md5 string&!! unset
26637 This option must be set for the authenticator to work as a client. Its value is
26638 expanded and the result used as the secret string when computing the response.
26642 .vindex "&$host_address$&"
26643 Different user names and secrets can be used for different servers by referring
26644 to &$host$& or &$host_address$& in the options. Forced failure of either
26645 expansion string is treated as an indication that this authenticator is not
26646 prepared to handle this case. Exim moves on to the next configured client
26647 authenticator. Any other expansion failure causes Exim to give up trying to
26648 send the message to the current server.
26650 A simple example configuration of a &(cram_md5)& authenticator, using fixed
26655 public_name = CRAM-MD5
26657 client_secret = secret
26659 .ecindex IIDcramauth1
26660 .ecindex IIDcramauth2
26664 . ////////////////////////////////////////////////////////////////////////////
26665 . ////////////////////////////////////////////////////////////////////////////
26667 .chapter "The cyrus_sasl authenticator" "CHID10"
26668 .scindex IIDcyrauth1 "&(cyrus_sasl)& authenticator"
26669 .scindex IIDcyrauth2 "authenticators" "&(cyrus_sasl)&"
26670 .cindex "Cyrus" "SASL library"
26672 The code for this authenticator was provided by Matthew Byng-Maddick of A L
26673 Digital Ltd (&url(http://www.aldigital.co.uk)).
26675 The &(cyrus_sasl)& authenticator provides server support for the Cyrus SASL
26676 library implementation of the RFC 2222 (&"Simple Authentication and Security
26677 Layer"&). This library supports a number of authentication mechanisms,
26678 including PLAIN and LOGIN, but also several others that Exim does not support
26679 directly. In particular, there is support for Kerberos authentication.
26681 The &(cyrus_sasl)& authenticator provides a gatewaying mechanism directly to
26682 the Cyrus interface, so if your Cyrus library can do, for example, CRAM-MD5,
26683 then so can the &(cyrus_sasl)& authenticator. By default it uses the public
26684 name of the driver to determine which mechanism to support.
26686 Where access to some kind of secret file is required, for example in GSSAPI
26687 or CRAM-MD5, it is worth noting that the authenticator runs as the Exim
26688 user, and that the Cyrus SASL library has no way of escalating privileges
26689 by default. You may also find you need to set environment variables,
26690 depending on the driver you are using.
26692 The application name provided by Exim is &"exim"&, so various SASL options may
26693 be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for
26694 Kerberos, note that because of limitations in the GSSAPI interface,
26695 changing the server keytab might need to be communicated down to the Kerberos
26696 layer independently. The mechanism for doing so is dependent upon the Kerberos
26699 For example, for older releases of Heimdal, the environment variable KRB5_KTNAME
26700 may be set to point to an alternative keytab file. Exim will pass this
26701 variable through from its own inherited environment when started as root or the
26702 Exim user. The keytab file needs to be readable by the Exim user.
26703 With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the
26704 environment variable. In practice, for those releases, the Cyrus authenticator
26705 is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider
26706 the &(heimdal_gssapi)& authenticator, described in chapter &<<CHAPheimdalgss>>&
26709 .section "Using cyrus_sasl as a server" "SECID178"
26710 The &(cyrus_sasl)& authenticator has four private options. It puts the username
26711 (on a successful authentication) into &$auth1$&. For compatibility with
26712 previous releases of Exim, the username is also placed in &$1$&. However, the
26713 use of this variable for this purpose is now deprecated, as it can lead to
26714 confusion in string expansions that also use numeric variables for other
26718 .option server_hostname cyrus_sasl string&!! "see below"
26719 This option selects the hostname that is used when communicating with the
26720 library. The default value is &`$primary_hostname`&. It is up to the underlying
26721 SASL plug-in what it does with this data.
26724 .option server_mech cyrus_sasl string "see below"
26725 This option selects the authentication mechanism this driver should use. The
26726 default is the value of the generic &%public_name%& option. This option allows
26727 you to use a different underlying mechanism from the advertised name. For
26731 driver = cyrus_sasl
26732 public_name = X-ANYTHING
26733 server_mech = CRAM-MD5
26734 server_set_id = $auth1
26737 .option server_realm cyrus_sasl string&!! unset
26738 This specifies the SASL realm that the server claims to be in.
26741 .option server_service cyrus_sasl string &`smtp`&
26742 This is the SASL service that the server claims to implement.
26745 For straightforward cases, you do not need to set any of the authenticator's
26746 private options. All you need to do is to specify an appropriate mechanism as
26747 the public name. Thus, if you have a SASL library that supports CRAM-MD5 and
26748 PLAIN, you could have two authenticators as follows:
26751 driver = cyrus_sasl
26752 public_name = CRAM-MD5
26753 server_set_id = $auth1
26756 driver = cyrus_sasl
26757 public_name = PLAIN
26758 server_set_id = $auth2
26760 Cyrus SASL does implement the LOGIN authentication method, even though it is
26761 not a standard method. It is disabled by default in the source distribution,
26762 but it is present in many binary distributions.
26763 .ecindex IIDcyrauth1
26764 .ecindex IIDcyrauth2
26769 . ////////////////////////////////////////////////////////////////////////////
26770 . ////////////////////////////////////////////////////////////////////////////
26771 .chapter "The dovecot authenticator" "CHAPdovecot"
26772 .scindex IIDdcotauth1 "&(dovecot)& authenticator"
26773 .scindex IIDdcotauth2 "authenticators" "&(dovecot)&"
26774 This authenticator is an interface to the authentication facility of the
26775 Dovecot POP/IMAP server, which can support a number of authentication methods.
26776 Note that Dovecot must be configured to use auth-client not auth-userdb.
26777 If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful
26778 to use the same mechanisms for SMTP authentication. This is a server
26779 authenticator only. There is only one option:
26781 .option server_socket dovecot string unset
26783 This option must specify the UNIX socket that is the interface to Dovecot
26784 authentication. The &%public_name%& option must specify an authentication
26785 mechanism that Dovecot is configured to support. You can have several
26786 authenticators for different mechanisms. For example:
26790 public_name = PLAIN
26791 server_socket = /var/run/dovecot/auth-client
26792 server_set_id = $auth1
26797 server_socket = /var/run/dovecot/auth-client
26798 server_set_id = $auth1
26800 If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to
26801 &$received_ip_address$& (that is, the connection is local), the &"secured"&
26802 option is passed in the Dovecot authentication command. If, for a TLS
26803 connection, a client certificate has been verified, the &"valid-client-cert"&
26804 option is passed. When authentication succeeds, the identity of the user
26805 who authenticated is placed in &$auth1$&.
26806 .ecindex IIDdcotauth1
26807 .ecindex IIDdcotauth2
26810 . ////////////////////////////////////////////////////////////////////////////
26811 . ////////////////////////////////////////////////////////////////////////////
26812 .chapter "The gsasl authenticator" "CHAPgsasl"
26813 .scindex IIDgsaslauth1 "&(gsasl)& authenticator"
26814 .scindex IIDgsaslauth2 "authenticators" "&(gsasl)&"
26815 .cindex "authentication" "GNU SASL"
26816 .cindex "authentication" "SASL"
26817 .cindex "authentication" "EXTERNAL"
26818 .cindex "authentication" "ANONYMOUS"
26819 .cindex "authentication" "PLAIN"
26820 .cindex "authentication" "LOGIN"
26821 .cindex "authentication" "DIGEST-MD5"
26822 .cindex "authentication" "CRAM-MD5"
26823 .cindex "authentication" "SCRAM-SHA-1"
26824 The &(gsasl)& authenticator provides server integration for the GNU SASL
26825 library and the mechanisms it provides. This is new as of the 4.80 release
26826 and there are a few areas where the library does not let Exim smoothly
26827 scale to handle future authentication mechanisms, so no guarantee can be
26828 made that any particular new authentication mechanism will be supported
26829 without code changes in Exim.
26832 .option server_channelbinding gsasl boolean false
26833 Some authentication mechanisms are able to use external context at both ends
26834 of the session to bind the authentication to that context, and fail the
26835 authentication process if that context differs. Specifically, some TLS
26836 ciphersuites can provide identifying information about the cryptographic
26839 This means that certificate identity and verification becomes a non-issue,
26840 as a man-in-the-middle attack will cause the correct client and server to
26841 see different identifiers and authentication will fail.
26843 This is currently only supported when using the GnuTLS library. This is
26844 only usable by mechanisms which support "channel binding"; at time of
26845 writing, that's the SCRAM family.
26847 This defaults off to ensure smooth upgrade across Exim releases, in case
26848 this option causes some clients to start failing. Some future release
26849 of Exim may switch the default to be true.
26852 .option server_hostname gsasl string&!! "see below"
26853 This option selects the hostname that is used when communicating with the
26854 library. The default value is &`$primary_hostname`&.
26855 Some mechanisms will use this data.
26858 .option server_mech gsasl string "see below"
26859 This option selects the authentication mechanism this driver should use. The
26860 default is the value of the generic &%public_name%& option. This option allows
26861 you to use a different underlying mechanism from the advertised name. For
26866 public_name = X-ANYTHING
26867 server_mech = CRAM-MD5
26868 server_set_id = $auth1
26872 .option server_password gsasl string&!! unset
26873 Various mechanisms need access to the cleartext password on the server, so
26874 that proof-of-possession can be demonstrated on the wire, without sending
26875 the password itself.
26877 The data available for lookup varies per mechanism.
26878 In all cases, &$auth1$& is set to the &'authentication id'&.
26879 The &$auth2$& variable will always be the &'authorization id'& (&'authz'&)
26880 if available, else the empty string.
26881 The &$auth3$& variable will always be the &'realm'& if available,
26882 else the empty string.
26884 A forced failure will cause authentication to defer.
26886 If using this option, it may make sense to set the &%server_condition%&
26887 option to be simply "true".
26890 .option server_realm gsasl string&!! unset
26891 This specifies the SASL realm that the server claims to be in.
26892 Some mechanisms will use this data.
26895 .option server_scram_iter gsasl string&!! unset
26896 This option provides data for the SCRAM family of mechanisms.
26897 &$auth1$& is not available at evaluation time.
26898 (This may change, as we receive feedback on use)
26901 .option server_scram_salt gsasl string&!! unset
26902 This option provides data for the SCRAM family of mechanisms.
26903 &$auth1$& is not available at evaluation time.
26904 (This may change, as we receive feedback on use)
26907 .option server_service gsasl string &`smtp`&
26908 This is the SASL service that the server claims to implement.
26909 Some mechanisms will use this data.
26912 .section "&(gsasl)& auth variables" "SECTgsaslauthvar"
26913 .vindex "&$auth1$&, &$auth2$&, etc"
26914 These may be set when evaluating specific options, as detailed above.
26915 They will also be set when evaluating &%server_condition%&.
26917 Unless otherwise stated below, the &(gsasl)& integration will use the following
26918 meanings for these variables:
26921 .vindex "&$auth1$&"
26922 &$auth1$&: the &'authentication id'&
26924 .vindex "&$auth2$&"
26925 &$auth2$&: the &'authorization id'&
26927 .vindex "&$auth3$&"
26928 &$auth3$&: the &'realm'&
26931 On a per-mechanism basis:
26934 .cindex "authentication" "EXTERNAL"
26935 EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&;
26936 the &%server_condition%& option must be present.
26938 .cindex "authentication" "ANONYMOUS"
26939 ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&;
26940 the &%server_condition%& option must be present.
26942 .cindex "authentication" "GSSAPI"
26943 GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&;
26944 &$auth2$& will be set to the &'authorization id'&,
26945 the &%server_condition%& option must be present.
26948 An &'anonymous token'& is something passed along as an unauthenticated
26949 identifier; this is analogous to FTP anonymous authentication passing an
26950 email address, or software-identifier@, as the "password".
26953 An example showing the password having the realm specified in the callback
26954 and demonstrating a Cyrus SASL to GSASL migration approach is:
26956 gsasl_cyrusless_crammd5:
26958 public_name = CRAM-MD5
26959 server_realm = imap.example.org
26960 server_password = ${lookup{$auth1:$auth3:userPassword}\
26961 dbmjz{/etc/sasldb2}{$value}fail}
26962 server_set_id = ${quote:$auth1}
26963 server_condition = yes
26967 . ////////////////////////////////////////////////////////////////////////////
26968 . ////////////////////////////////////////////////////////////////////////////
26970 .chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss"
26971 .scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator"
26972 .scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&"
26973 .cindex "authentication" "GSSAPI"
26974 .cindex "authentication" "Kerberos"
26975 The &(heimdal_gssapi)& authenticator provides server integration for the
26976 Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname
26979 .option server_hostname heimdal_gssapi string&!! "see below"
26980 This option selects the hostname that is used, with &%server_service%&,
26981 for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'&
26982 identifier. The default value is &`$primary_hostname`&.
26984 .option server_keytab heimdal_gssapi string&!! unset
26985 If set, then Heimdal will not use the system default keytab (typically
26986 &_/etc/krb5.keytab_&) but instead the pathname given in this option.
26987 The value should be a pathname, with no &"file:"& prefix.
26989 .option server_service heimdal_gssapi string&!! "smtp"
26990 This option specifies the service identifier used, in conjunction with
26991 &%server_hostname%&, for building the identifier for finding credentials
26995 .section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar"
26996 Beware that these variables will typically include a realm, thus will appear
26997 to be roughly like an email address already. The &'authzid'& in &$auth2$& is
26998 not verified, so a malicious client can set it to anything.
27000 The &$auth1$& field should be safely trustable as a value from the Key
27001 Distribution Center. Note that these are not quite email addresses.
27002 Each identifier is for a role, and so the left-hand-side may include a
27003 role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&.
27005 .vindex "&$auth1$&, &$auth2$&, etc"
27007 .vindex "&$auth1$&"
27008 &$auth1$&: the &'authentication id'&, set to the GSS Display Name.
27010 .vindex "&$auth2$&"
27011 &$auth2$&: the &'authorization id'&, sent within SASL encapsulation after
27012 authentication. If that was empty, this will also be set to the
27017 . ////////////////////////////////////////////////////////////////////////////
27018 . ////////////////////////////////////////////////////////////////////////////
27020 .chapter "The spa authenticator" "CHAPspa"
27021 .scindex IIDspaauth1 "&(spa)& authenticator"
27022 .scindex IIDspaauth2 "authenticators" "&(spa)&"
27023 .cindex "authentication" "Microsoft Secure Password"
27024 .cindex "authentication" "NTLM"
27025 .cindex "Microsoft Secure Password Authentication"
27026 .cindex "NTLM authentication"
27027 The &(spa)& authenticator provides client support for Microsoft's &'Secure
27028 Password Authentication'& mechanism,
27029 which is also sometimes known as NTLM (NT LanMan). The code for client side of
27030 this authenticator was contributed by Marc Prud'hommeaux, and much of it is
27031 taken from the Samba project (&url(http://www.samba.org)). The code for the
27032 server side was subsequently contributed by Tom Kistner. The mechanism works as
27036 After the AUTH command has been accepted, the client sends an SPA
27037 authentication request based on the user name and optional domain.
27039 The server sends back a challenge.
27041 The client builds a challenge response which makes use of the user's password
27042 and sends it to the server, which then accepts or rejects it.
27045 Encryption is used to protect the password in transit.
27049 .section "Using spa as a server" "SECID179"
27050 .cindex "options" "&(spa)& authenticator (server)"
27051 The &(spa)& authenticator has just one server option:
27053 .option server_password spa string&!! unset
27054 .cindex "numerical variables (&$1$& &$2$& etc)" "in &(spa)& authenticator"
27055 This option is expanded, and the result must be the cleartext password for the
27056 authenticating user, whose name is at this point in &$auth1$&. For
27057 compatibility with previous releases of Exim, the user name is also placed in
27058 &$1$&. However, the use of this variable for this purpose is now deprecated, as
27059 it can lead to confusion in string expansions that also use numeric variables
27060 for other things. For example:
27065 server_password = \
27066 ${lookup{$auth1}lsearch{/etc/exim/spa_clearpass}{$value}fail}
27068 If the expansion is forced to fail, authentication fails. Any other expansion
27069 failure causes a temporary error code to be returned.
27075 .section "Using spa as a client" "SECID180"
27076 .cindex "options" "&(spa)& authenticator (client)"
27077 The &(spa)& authenticator has the following client options:
27081 .option client_domain spa string&!! unset
27082 This option specifies an optional domain for the authentication.
27085 .option client_password spa string&!! unset
27086 This option specifies the user's password, and must be set.
27089 .option client_username spa string&!! unset
27090 This option specifies the user name, and must be set. Here is an example of a
27091 configuration of this authenticator for use with the mail servers at
27097 client_username = msn/msn_username
27098 client_password = msn_plaintext_password
27099 client_domain = DOMAIN_OR_UNSET
27101 .ecindex IIDspaauth1
27102 .ecindex IIDspaauth2
27108 . ////////////////////////////////////////////////////////////////////////////
27109 . ////////////////////////////////////////////////////////////////////////////
27111 .chapter "The tls authenticator" "CHAPtlsauth"
27112 .scindex IIDtlsauth1 "&(tls)& authenticator"
27113 .scindex IIDtlsauth2 "authenticators" "&(tls)&"
27114 .cindex "authentication" "Client Certificate"
27115 .cindex "authentication" "X509"
27116 .cindex "Certificate-based authentication"
27117 The &(tls)& authenticator provides server support for
27118 authentication based on client certificates.
27120 It is not an SMTP authentication mechanism and is not
27121 advertised by the server as part of the SMTP EHLO response.
27122 It is an Exim authenticator in the sense that it affects
27123 the protocol element of the log line, can be tested for
27124 by the &%authenticated%& ACL condition, and can set
27125 the &$authenticated_id$& variable.
27127 The client must present a verifiable certificate,
27128 for which it must have been requested via the
27129 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& main options
27130 (see &<<CHAPTLS>>&).
27132 If an authenticator of this type is configured it is
27133 run before any SMTP-level communication is done,
27134 and can authenticate the connection.
27135 If it does, SMTP authentication is not offered.
27137 A maximum of one authenticator of this type may be present.
27140 .cindex "options" "&(tls)& authenticator (server)"
27141 The &(tls)& authenticator has three server options:
27143 .option server_param1 tls string&!! unset
27144 .cindex "variables (&$auth1$& &$auth2$& etc)" "in &(tls)& authenticator"
27145 This option is expanded after the TLS negotiation and
27146 the result is placed in &$auth1$&.
27147 If the expansion is forced to fail, authentication fails. Any other expansion
27148 failure causes a temporary error code to be returned.
27150 .option server_param2 tls string&!! unset
27151 .option server_param3 tls string&!! unset
27152 As above, for &$auth2$& and &$auth3$&.
27154 &%server_param1%& may also be spelled &%server_param%&.
27161 server_param1 = ${certextract {subj_altname,mail,>:} \
27162 {$tls_in_peercert}}
27163 server_condition = ${if forany {$auth1} \
27165 {${lookup ldap{ldap:///\
27166 mailname=${quote_ldap_dn:${lc:$item}},\
27167 ou=users,LDAP_DC?mailid} {$value}{0} \
27169 server_set_id = ${if = {1}{${listcount:$auth1}} {$auth1}{}}
27171 This accepts a client certificate that is verifiable against any
27172 of your configured trust-anchors
27173 (which usually means the full set of public CAs)
27174 and which has a SAN with a good account name.
27175 Note that the client cert is on the wire in-clear, including the SAN,
27176 whereas a plaintext SMTP AUTH done inside TLS is not.
27178 . An alternative might use
27180 . server_param1 = ${sha256:$tls_in_peercert}
27182 . to require one of a set of specific certs that define a given account
27183 . (the verification is still required, but mostly irrelevant).
27184 . This would help for per-device use.
27186 . However, for the future we really need support for checking a
27187 . user cert in LDAP - which probably wants a base-64 DER.
27189 .ecindex IIDtlsauth1
27190 .ecindex IIDtlsauth2
27193 Note that because authentication is traditionally an SMTP operation,
27194 the &%authenticated%& ACL condition cannot be used in
27195 a connect- or helo-ACL.
27199 . ////////////////////////////////////////////////////////////////////////////
27200 . ////////////////////////////////////////////////////////////////////////////
27202 .chapter "Encrypted SMTP connections using TLS/SSL" "CHAPTLS" &&&
27203 "Encrypted SMTP connections"
27204 .scindex IIDencsmtp1 "encryption" "on SMTP connection"
27205 .scindex IIDencsmtp2 "SMTP" "encryption"
27206 .cindex "TLS" "on SMTP connection"
27209 Support for TLS (Transport Layer Security), formerly known as SSL (Secure
27210 Sockets Layer), is implemented by making use of the OpenSSL library or the
27211 GnuTLS library (Exim requires GnuTLS release 1.0 or later). There is no
27212 cryptographic code in the Exim distribution itself for implementing TLS. In
27213 order to use this feature you must install OpenSSL or GnuTLS, and then build a
27214 version of Exim that includes TLS support (see section &<<SECTinctlsssl>>&).
27215 You also need to understand the basic concepts of encryption at a managerial
27216 level, and in particular, the way that public keys, private keys, and
27217 certificates are used.
27219 RFC 3207 defines how SMTP connections can make use of encryption. Once a
27220 connection is established, the client issues a STARTTLS command. If the
27221 server accepts this, the client and the server negotiate an encryption
27222 mechanism. If the negotiation succeeds, the data that subsequently passes
27223 between them is encrypted.
27225 Exim's ACLs can detect whether the current SMTP session is encrypted or not,
27226 and if so, what cipher suite is in use, whether the client supplied a
27227 certificate, and whether or not that certificate was verified. This makes it
27228 possible for an Exim server to deny or accept certain commands based on the
27231 &*Warning*&: Certain types of firewall and certain anti-virus products can
27232 disrupt TLS connections. You need to turn off SMTP scanning for these products
27233 in order to get TLS to work.
27237 .section "Support for the &""submissions""& (aka &""ssmtp""& and &""smtps""&) protocol" &&&
27239 .cindex "submissions protocol"
27240 .cindex "ssmtp protocol"
27241 .cindex "smtps protocol"
27242 .cindex "SMTP" "submissions protocol"
27243 .cindex "SMTP" "ssmtp protocol"
27244 .cindex "SMTP" "smtps protocol"
27245 The history of port numbers for TLS in SMTP is a little messy and has been
27246 contentious. As of RFC 8314, the common practice of using the historically
27247 allocated port 465 for "email submission but with TLS immediately upon connect
27248 instead of using STARTTLS" is officially blessed by the IETF, and recommended
27249 by them in preference to STARTTLS.
27251 The name originally assigned to the port was &"ssmtp"& or &"smtps"&, but as
27252 clarity emerged over the dual roles of SMTP, for MX delivery and Email
27253 Submission, nomenclature has shifted. The modern name is now &"submissions"&.
27255 This approach was, for a while, officially abandoned when encrypted SMTP was
27256 standardized, but many clients kept using it, even as the TCP port number was
27257 reassigned for other use.
27258 Thus you may encounter guidance claiming that you shouldn't enable use of
27260 In practice, a number of mail-clients have only ever supported submissions,
27261 not submission with STARTTLS upgrade.
27262 Ideally, offer both submission (587) and submissions (465) service.
27264 Exim supports TLS-on-connect by means of the &%tls_on_connect_ports%&
27265 global option. Its value must be a list of port numbers;
27266 the most common use is expected to be:
27268 tls_on_connect_ports = 465
27270 The port numbers specified by this option apply to all SMTP connections, both
27271 via the daemon and via &'inetd'&. You still need to specify all the ports that
27272 the daemon uses (by setting &%daemon_smtp_ports%& or &%local_interfaces%& or
27273 the &%-oX%& command line option) because &%tls_on_connect_ports%& does not add
27274 an extra port &-- rather, it specifies different behaviour on a port that is
27277 There is also a &%-tls-on-connect%& command line option. This overrides
27278 &%tls_on_connect_ports%&; it forces the TLS-only behaviour for all ports.
27285 .section "OpenSSL vs GnuTLS" "SECTopenvsgnu"
27286 .cindex "TLS" "OpenSSL &'vs'& GnuTLS"
27287 The first TLS support in Exim was implemented using OpenSSL. Support for GnuTLS
27288 followed later, when the first versions of GnuTLS were released. To build Exim
27289 to use GnuTLS, you need to set
27293 in Local/Makefile, in addition to
27297 You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the
27298 include files and libraries for GnuTLS can be found.
27300 There are some differences in usage when using GnuTLS instead of OpenSSL:
27303 The &%tls_verify_certificates%& option
27304 cannot be the path of a directory
27305 for GnuTLS versions before 3.3.6
27306 (for later versions, or OpenSSL, it can be either).
27308 The default value for &%tls_dhparam%& differs for historical reasons.
27310 .vindex "&$tls_in_peerdn$&"
27311 .vindex "&$tls_out_peerdn$&"
27312 Distinguished Name (DN) strings reported by the OpenSSL library use a slash for
27313 separating fields; GnuTLS uses commas, in accordance with RFC 2253. This
27314 affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables.
27316 OpenSSL identifies cipher suites using hyphens as separators, for example:
27317 DES-CBC3-SHA. GnuTLS historically used underscores, for example:
27318 RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present
27319 in a cipher list. To make life simpler, Exim changes underscores to hyphens
27320 for OpenSSL and passes the string unchanged to GnuTLS (expecting the library
27321 to handle its own older variants) when processing lists of cipher suites in the
27322 &%tls_require_ciphers%& options (the global option and the &(smtp)& transport
27325 The &%tls_require_ciphers%& options operate differently, as described in the
27326 sections &<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
27328 The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS.
27329 When using OpenSSL, this option is ignored.
27330 (If an API is found to let OpenSSL be configured in this way,
27331 let the Exim Maintainers know and we'll likely use it).
27333 With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
27334 main option, it must be ordered to match the &%tls_certificate%& list.
27336 Some other recently added features may only be available in one or the other.
27337 This should be documented with the feature. If the documentation does not
27338 explicitly state that the feature is infeasible in the other TLS
27339 implementation, then patches are welcome.
27343 .section "GnuTLS parameter computation" "SECTgnutlsparam"
27344 This section only applies if &%tls_dhparam%& is set to &`historic`& or to
27345 an explicit path; if the latter, then the text about generation still applies,
27346 but not the chosen filename.
27347 By default, as of Exim 4.80 a hard-coded D-H prime is used.
27348 See the documentation of &%tls_dhparam%& for more information.
27350 GnuTLS uses D-H parameters that may take a substantial amount of time
27351 to compute. It is unreasonable to re-compute them for every TLS session.
27352 Therefore, Exim keeps this data in a file in its spool directory, called
27353 &_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number
27355 The file is owned by the Exim user and is readable only by
27356 its owner. Every Exim process that start up GnuTLS reads the D-H
27357 parameters from this file. If the file does not exist, the first Exim process
27358 that needs it computes the data and writes it to a temporary file which is
27359 renamed once it is complete. It does not matter if several Exim processes do
27360 this simultaneously (apart from wasting a few resources). Once a file is in
27361 place, new Exim processes immediately start using it.
27363 For maximum security, the parameters that are stored in this file should be
27364 recalculated periodically, the frequency depending on your paranoia level.
27365 If you are avoiding using the fixed D-H primes published in RFCs, then you
27366 are concerned about some advanced attacks and will wish to do this; if you do
27367 not regenerate then you might as well stick to the standard primes.
27369 Arranging this is easy in principle; just delete the file when you want new
27370 values to be computed. However, there may be a problem. The calculation of new
27371 parameters needs random numbers, and these are obtained from &_/dev/random_&.
27372 If the system is not very active, &_/dev/random_& may delay returning data
27373 until enough randomness (entropy) is available. This may cause Exim to hang for
27374 a substantial amount of time, causing timeouts on incoming connections.
27376 The solution is to generate the parameters externally to Exim. They are stored
27377 in &_gnutls-params-N_& in PEM format, which means that they can be
27378 generated externally using the &(certtool)& command that is part of GnuTLS.
27380 To replace the parameters with new ones, instead of deleting the file
27381 and letting Exim re-create it, you can generate new parameters using
27382 &(certtool)& and, when this has been done, replace Exim's cache file by
27383 renaming. The relevant commands are something like this:
27386 [ look for file; assume gnutls-params-2236 is the most recent ]
27389 # chown exim:exim new-params
27390 # chmod 0600 new-params
27391 # certtool --generate-dh-params --bits 2236 >>new-params
27392 # openssl dhparam -noout -text -in new-params | head
27393 [ check the first line, make sure it's not more than 2236;
27394 if it is, then go back to the start ("rm") and repeat
27395 until the size generated is at most the size requested ]
27396 # chmod 0400 new-params
27397 # mv new-params gnutls-params-2236
27399 If Exim never has to generate the parameters itself, the possibility of
27400 stalling is removed.
27402 The filename changed in Exim 4.80, to gain the -bits suffix. The value which
27403 Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS,
27404 the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is
27405 a way for Exim to ask for the "normal" number of bits for D-H public-key usage,
27406 and Exim does so. This attempt to remove Exim from TLS policy decisions
27407 failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit
27408 of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option,
27409 which applies to all D-H usage, client or server. If the value returned by
27410 GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down
27411 to &%tls_dh_max_bits%&. The default value has been set at the current NSS
27412 limit, which is still much higher than Exim historically used.
27414 The filename and bits used will change as the GnuTLS maintainers change the
27415 value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by
27416 &%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends
27417 2432 bits, while NSS is limited to 2236 bits.
27419 In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to
27420 increase the chance of the generated prime actually being within acceptable
27421 bounds, as GnuTLS has been observed to overshoot. Note the check step in the
27422 procedure above. There is no sane procedure available to Exim to double-check
27423 the size of the generated prime, so it might still be too large.
27426 .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl"
27427 .cindex "TLS" "requiring specific ciphers (OpenSSL)"
27428 .oindex "&%tls_require_ciphers%&" "OpenSSL"
27429 There is a function in the OpenSSL library that can be passed a list of cipher
27430 suites before the cipher negotiation takes place. This specifies which ciphers
27432 are acceptable for TLS versions prior to 1.3.
27434 The list is colon separated and may contain names like
27435 DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%&
27436 directly to this function call.
27437 Many systems will install the OpenSSL manual-pages, so you may have
27438 &'ciphers(1)'& available to you.
27439 The following quotation from the OpenSSL
27440 documentation specifies what forms of item are allowed in the cipher string:
27443 It can consist of a single cipher suite such as RC4-SHA.
27445 It can represent a list of cipher suites containing a certain algorithm,
27446 or cipher suites of a certain type. For example SHA1 represents all
27447 ciphers suites using the digest algorithm SHA1 and SSLv3 represents all
27450 Lists of cipher suites can be combined in a single cipher string using
27451 the + character. This is used as a logical and operation. For example
27452 SHA1+DES represents all cipher suites containing the SHA1 and the DES
27456 Each cipher string can be optionally preceded by one of the characters &`!`&,
27459 If &`!`& is used, the ciphers are permanently deleted from the list. The
27460 ciphers deleted can never reappear in the list even if they are explicitly
27463 If &`-`& is used, the ciphers are deleted from the list, but some or all
27464 of the ciphers can be added again by later options.
27466 If &`+`& is used, the ciphers are moved to the end of the list. This
27467 option does not add any new ciphers; it just moves matching existing ones.
27470 If none of these characters is present, the string is interpreted as
27471 a list of ciphers to be appended to the current preference list. If the list
27472 includes any ciphers already present they will be ignored: that is, they will
27473 not be moved to the end of the list.
27476 The OpenSSL &'ciphers(1)'& command may be used to test the results of a given
27479 # note single-quotes to get ! past any shell history expansion
27480 $ openssl ciphers 'HIGH:!MD5:!SHA1'
27483 This example will let the library defaults be permitted on the MX port, where
27484 there's probably no identity verification anyway, but ups the ante on the
27485 submission ports where the administrator might have some influence on the
27486 choice of clients used:
27488 # OpenSSL variant; see man ciphers(1)
27489 tls_require_ciphers = ${if =={$received_port}{25}\
27494 This example will prefer ECDSA-authenticated ciphers over RSA ones:
27496 tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
27500 For TLS version 1.3 the control available is less fine-grained
27501 and Exim does not provide access to it at present.
27502 The value of the &%tls_require_ciphers%& option is ignored when
27503 TLS version 1.3 is negotiated.
27505 As of writing the library default cipher suite list for TLSv1.3 is
27507 TLS_AES_256_GCM_SHA384:TLS_CHACHA20_POLY1305_SHA256:TLS_AES_128_GCM_SHA256
27512 .section "Requiring specific ciphers or other parameters in GnuTLS" &&&
27514 .cindex "GnuTLS" "specifying parameters for"
27515 .cindex "TLS" "specifying ciphers (GnuTLS)"
27516 .cindex "TLS" "specifying key exchange methods (GnuTLS)"
27517 .cindex "TLS" "specifying MAC algorithms (GnuTLS)"
27518 .cindex "TLS" "specifying protocols (GnuTLS)"
27519 .cindex "TLS" "specifying priority string (GnuTLS)"
27520 .oindex "&%tls_require_ciphers%&" "GnuTLS"
27521 The GnuTLS library allows the caller to provide a "priority string", documented
27522 as part of the &[gnutls_priority_init]& function. This is very similar to the
27523 ciphersuite specification in OpenSSL.
27525 The &%tls_require_ciphers%& option is treated as the GnuTLS priority string
27526 and controls both protocols and ciphers.
27528 The &%tls_require_ciphers%& option is available both as an global option,
27529 controlling how Exim behaves as a server, and also as an option of the
27530 &(smtp)& transport, controlling how Exim behaves as a client. In both cases
27531 the value is string expanded. The resulting string is not an Exim list and
27532 the string is given to the GnuTLS library, so that Exim does not need to be
27533 aware of future feature enhancements of GnuTLS.
27535 Documentation of the strings accepted may be found in the GnuTLS manual, under
27536 "Priority strings". This is online as
27537 &url(http://www.gnutls.org/manual/html_node/Priority-Strings.html),
27538 but beware that this relates to GnuTLS 3, which may be newer than the version
27539 installed on your system. If you are using GnuTLS 3,
27540 then the example code
27541 &url(http://www.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string)
27542 on that site can be used to test a given string.
27546 # Disable older versions of protocols
27547 tls_require_ciphers = NORMAL:%LATEST_RECORD_VERSION:-VERS-SSL3.0
27550 Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three
27551 additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and
27552 "&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list.
27554 This example will let the library defaults be permitted on the MX port, where
27555 there's probably no identity verification anyway, and lowers security further
27556 by increasing compatibility; but this ups the ante on the submission ports
27557 where the administrator might have some influence on the choice of clients
27561 tls_require_ciphers = ${if =={$received_port}{25}\
27567 .section "Configuring an Exim server to use TLS" "SECID182"
27568 .cindex "TLS" "configuring an Exim server"
27569 When Exim has been built with TLS support, it advertises the availability of
27570 the STARTTLS command to client hosts that match &%tls_advertise_hosts%&,
27571 but not to any others. The default value of this option is *, which means
27572 that STARTTLS is always advertised. Set it to blank to never advertise;
27573 this is reasonable for systems that want to use TLS only as a client.
27575 If STARTTLS is to be used you
27576 need to set some other options in order to make TLS available.
27578 If a client issues a STARTTLS command and there is some configuration
27579 problem in the server, the command is rejected with a 454 error. If the client
27580 persists in trying to issue SMTP commands, all except QUIT are rejected
27583 554 Security failure
27585 If a STARTTLS command is issued within an existing TLS session, it is
27586 rejected with a 554 error code.
27588 To enable TLS operations on a server, the &%tls_advertise_hosts%& option
27589 must be set to match some hosts. The default is * which matches all hosts.
27591 If this is all you do, TLS encryption will be enabled but not authentication -
27592 meaning that the peer has no assurance it is actually you he is talking to.
27593 You gain protection from a passive sniffer listening on the wire but not
27594 from someone able to intercept the communication.
27596 Further protection requires some further configuration at the server end.
27598 To make TLS work you need to set, in the server,
27600 tls_certificate = /some/file/name
27601 tls_privatekey = /some/file/name
27603 These options are, in fact, expanded strings, so you can make them depend on
27604 the identity of the client that is connected if you wish. The first file
27605 contains the server's X509 certificate, and the second contains the private key
27606 that goes with it. These files need to be
27607 PEM format and readable by the Exim user, and must
27608 always be given as full path names.
27609 The key must not be password-protected.
27610 They can be the same file if both the
27611 certificate and the key are contained within it. If &%tls_privatekey%& is not
27612 set, or if its expansion is forced to fail or results in an empty string, this
27613 is assumed to be the case. The certificate file may also contain intermediate
27614 certificates that need to be sent to the client to enable it to authenticate
27615 the server's certificate.
27617 For dual-stack (eg. RSA and ECDSA) configurations, these options can be
27618 colon-separated lists of file paths. Ciphers using given authentication
27619 algorithms require the presence of a suitable certificate to supply the
27620 public-key. The server selects among the certificates to present to the
27621 client depending on the selected cipher, hence the priority ordering for
27622 ciphers will affect which certificate is used.
27624 If you do not understand about certificates and keys, please try to find a
27625 source of this background information, which is not Exim-specific. (There are a
27626 few comments below in section &<<SECTcerandall>>&.)
27628 &*Note*&: These options do not apply when Exim is operating as a client &--
27629 they apply only in the case of a server. If you need to use a certificate in an
27630 Exim client, you must set the options of the same names in an &(smtp)&
27633 With just these options, an Exim server will be able to use TLS. It does not
27634 require the client to have a certificate (but see below for how to insist on
27635 this). There is one other option that may be needed in other situations. If
27637 tls_dhparam = /some/file/name
27639 is set, the SSL library is initialized for the use of Diffie-Hellman ciphers
27640 with the parameters contained in the file.
27641 Set this to &`none`& to disable use of DH entirely, by making no prime
27646 This may also be set to a string identifying a standard prime to be used for
27647 DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime
27648 used is &`ike23`&. There are a few standard primes available, see the
27649 documentation for &%tls_dhparam%& for the complete list.
27655 for a way of generating file data.
27657 The strings supplied for these three options are expanded every time a client
27658 host connects. It is therefore possible to use different certificates and keys
27659 for different hosts, if you so wish, by making use of the client's IP address
27660 in &$sender_host_address$& to control the expansion. If a string expansion is
27661 forced to fail, Exim behaves as if the option is not set.
27663 .cindex "cipher" "logging"
27664 .cindex "log" "TLS cipher"
27665 .vindex "&$tls_in_cipher$&"
27666 The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for
27667 an incoming TLS connection. It is included in the &'Received:'& header of an
27668 incoming message (by default &-- you can, of course, change this), and it is
27669 also included in the log line that records a message's arrival, keyed by
27670 &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%&
27671 condition can be used to test for specific cipher suites in ACLs.
27673 Once TLS has been established, the ACLs that run for subsequent SMTP commands
27674 can check the name of the cipher suite and vary their actions accordingly. The
27675 cipher suite names vary, depending on which TLS library is being used. For
27676 example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other
27677 contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS
27678 documentation for more details.
27680 For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged
27681 (again depending on the &%tls_cipher%& log selector).
27684 .section "Requesting and verifying client certificates" "SECID183"
27685 .cindex "certificate" "verification of client"
27686 .cindex "TLS" "client certificate verification"
27687 If you want an Exim server to request a certificate when negotiating a TLS
27688 session with a client, you must set either &%tls_verify_hosts%& or
27689 &%tls_try_verify_hosts%&. You can, of course, set either of them to * to
27690 apply to all TLS connections. For any host that matches one of these options,
27691 Exim requests a certificate as part of the setup of the TLS session. The
27692 contents of the certificate are verified by comparing it with a list of
27693 expected certificates.
27694 These may be the system default set (depending on library version),
27695 an explicit file or,
27696 depending on library version, a directory, identified by
27697 &%tls_verify_certificates%&.
27699 A file can contain multiple certificates, concatenated end to end. If a
27702 each certificate must be in a separate file, with a name (or a symbolic link)
27703 of the form <&'hash'&>.0, where <&'hash'&> is a hash value constructed from the
27704 certificate. You can compute the relevant hash by running the command
27706 openssl x509 -hash -noout -in /cert/file
27708 where &_/cert/file_& contains a single certificate.
27710 The difference between &%tls_verify_hosts%& and &%tls_try_verify_hosts%& is
27711 what happens if the client does not supply a certificate, or if the certificate
27712 does not match any of the certificates in the collection named by
27713 &%tls_verify_certificates%&. If the client matches &%tls_verify_hosts%&, the
27714 attempt to set up a TLS session is aborted, and the incoming connection is
27715 dropped. If the client matches &%tls_try_verify_hosts%&, the (encrypted) SMTP
27716 session continues. ACLs that run for subsequent SMTP commands can detect the
27717 fact that no certificate was verified, and vary their actions accordingly. For
27718 example, you can insist on a certificate before accepting a message for
27719 relaying, but not when the message is destined for local delivery.
27721 .vindex "&$tls_in_peerdn$&"
27722 When a client supplies a certificate (whether it verifies or not), the value of
27723 the Distinguished Name of the certificate is made available in the variable
27724 &$tls_in_peerdn$& during subsequent processing of the message.
27726 .cindex "log" "distinguished name"
27727 Because it is often a long text string, it is not included in the log line or
27728 &'Received:'& header by default. You can arrange for it to be logged, keyed by
27729 &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use
27730 &%received_header_text%& to change the &'Received:'& header. When no
27731 certificate is supplied, &$tls_in_peerdn$& is empty.
27734 .section "Revoked certificates" "SECID184"
27735 .cindex "TLS" "revoked certificates"
27736 .cindex "revocation list"
27737 .cindex "certificate" "revocation list"
27738 .cindex "OCSP" "stapling"
27739 Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when
27740 certificates are revoked. If you have such a list, you can pass it to an Exim
27741 server using the global option called &%tls_crl%& and to an Exim client using
27742 an identically named option for the &(smtp)& transport. In each case, the value
27743 of the option is expanded and must then be the name of a file that contains a
27745 The downside is that clients have to periodically re-download a potentially huge
27746 file from every certificate authority they know of.
27748 The way with most moving parts at query time is Online Certificate
27749 Status Protocol (OCSP), where the client verifies the certificate
27750 against an OCSP server run by the CA. This lets the CA track all
27751 usage of the certs. It requires running software with access to the
27752 private key of the CA, to sign the responses to the OCSP queries. OCSP
27753 is based on HTTP and can be proxied accordingly.
27755 The only widespread OCSP server implementation (known to this writer)
27756 comes as part of OpenSSL and aborts on an invalid request, such as
27757 connecting to the port and then disconnecting. This requires
27758 re-entering the passphrase each time some random client does this.
27760 The third way is OCSP Stapling; in this, the server using a certificate
27761 issued by the CA periodically requests an OCSP proof of validity from
27762 the OCSP server, then serves it up inline as part of the TLS
27763 negotiation. This approach adds no extra round trips, does not let the
27764 CA track users, scales well with number of certs issued by the CA and is
27765 resilient to temporary OCSP server failures, as long as the server
27766 starts retrying to fetch an OCSP proof some time before its current
27767 proof expires. The downside is that it requires server support.
27769 Unless Exim is built with the support disabled,
27770 or with GnuTLS earlier than version 3.3.16 / 3.4.8
27771 support for OCSP stapling is included.
27773 There is a global option called &%tls_ocsp_file%&.
27774 The file specified therein is expected to be in DER format, and contain
27775 an OCSP proof. Exim will serve it as part of the TLS handshake. This
27776 option will be re-expanded for SNI, if the &%tls_certificate%& option
27777 contains &`tls_in_sni`&, as per other TLS options.
27779 Exim does not at this time implement any support for fetching a new OCSP
27780 proof. The burden is on the administrator to handle this, outside of
27781 Exim. The file specified should be replaced atomically, so that the
27782 contents are always valid. Exim will expand the &%tls_ocsp_file%& option
27783 on each connection, so a new file will be handled transparently on the
27786 When built with OpenSSL Exim will check for a valid next update timestamp
27787 in the OCSP proof; if not present, or if the proof has expired, it will be
27790 For the client to be able to verify the stapled OCSP the server must
27791 also supply, in its stapled information, any intermediate
27792 certificates for the chain leading to the OCSP proof from the signer
27793 of the server certificate. There may be zero or one such. These
27794 intermediate certificates should be added to the server OCSP stapling
27795 file named by &%tls_ocsp_file%&.
27797 Note that the proof only covers the terminal server certificate,
27798 not any of the chain from CA to it.
27800 There is no current way to staple a proof for a client certificate.
27803 A helper script "ocsp_fetch.pl" for fetching a proof from a CA
27804 OCSP server is supplied. The server URL may be included in the
27805 server certificate, if the CA is helpful.
27807 One failure mode seen was the OCSP Signer cert expiring before the end
27808 of validity of the OCSP proof. The checking done by Exim/OpenSSL
27809 noted this as invalid overall, but the re-fetch script did not.
27815 .section "Configuring an Exim client to use TLS" "SECID185"
27816 .cindex "cipher" "logging"
27817 .cindex "log" "TLS cipher"
27818 .cindex "log" "distinguished name"
27819 .cindex "TLS" "configuring an Exim client"
27820 The &%tls_cipher%& and &%tls_peerdn%& log selectors apply to outgoing SMTP
27821 deliveries as well as to incoming, the latter one causing logging of the
27822 server certificate's DN. The remaining client configuration for TLS is all
27823 within the &(smtp)& transport.
27825 It is not necessary to set any options to have TLS work in the &(smtp)&
27826 transport. If Exim is built with TLS support, and TLS is advertised by a
27827 server, the &(smtp)& transport always tries to start a TLS session. However,
27828 this can be prevented by setting &%hosts_avoid_tls%& (an option of the
27829 transport) to a list of server hosts for which TLS should not be used.
27831 If you do not want Exim to attempt to send messages unencrypted when an attempt
27832 to set up an encrypted connection fails in any way, you can set
27833 &%hosts_require_tls%& to a list of hosts for which encryption is mandatory. For
27834 those hosts, delivery is always deferred if an encrypted connection cannot be
27835 set up. If there are any other hosts for the address, they are tried in the
27838 When the server host is not in &%hosts_require_tls%&, Exim may try to deliver
27839 the message unencrypted. It always does this if the response to STARTTLS is
27840 a 5&'xx'& code. For a temporary error code, or for a failure to negotiate a TLS
27841 session after a success response code, what happens is controlled by the
27842 &%tls_tempfail_tryclear%& option of the &(smtp)& transport. If it is false,
27843 delivery to this host is deferred, and other hosts (if available) are tried. If
27844 it is true, Exim attempts to deliver unencrypted after a 4&'xx'& response to
27845 STARTTLS, and if STARTTLS is accepted, but the subsequent TLS
27846 negotiation fails, Exim closes the current connection (because it is in an
27847 unknown state), opens a new one to the same host, and then tries the delivery
27850 The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
27851 transport provide the client with a certificate, which is passed to the server
27852 if it requests it. If the server is Exim, it will request a certificate only if
27853 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
27855 If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it
27856 specifies a collection of expected server certificates.
27858 the system default set (depending on library version),
27860 or (depending on library version) a directory.
27861 The client verifies the server's certificate
27862 against this collection, taking into account any revoked certificates that are
27863 in the list defined by &%tls_crl%&.
27864 Failure to verify fails the TLS connection unless either of the
27865 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& options are set.
27867 The &%tls_verify_hosts%& and &%tls_try_verify_hosts%& options restrict
27868 certificate verification to the listed servers. Verification either must
27869 or need not succeed respectively.
27871 The &(smtp)& transport has two OCSP-related options:
27872 &%hosts_require_ocsp%&; a host-list for which a Certificate Status
27873 is requested and required for the connection to proceed. The default
27875 &%hosts_request_ocsp%&; a host-list for which (additionally)
27876 a Certificate Status is requested (but not necessarily verified). The default
27877 value is "*" meaning that requests are made unless configured
27880 The host(s) should also be in &%hosts_require_tls%&, and
27881 &%tls_verify_certificates%& configured for the transport,
27882 for OCSP to be relevant.
27885 &%tls_require_ciphers%& is set on the &(smtp)& transport, it must contain a
27886 list of permitted cipher suites. If either of these checks fails, delivery to
27887 the current host is abandoned, and the &(smtp)& transport tries to deliver to
27888 alternative hosts, if any.
27891 These options must be set in the &(smtp)& transport for Exim to use TLS when it
27892 is operating as a client. Exim does not assume that a server certificate (set
27893 by the global options of the same name) should also be used when operating as a
27897 .vindex "&$host_address$&"
27898 All the TLS options in the &(smtp)& transport are expanded before use, with
27899 &$host$& and &$host_address$& containing the name and address of the server to
27900 which the client is connected. Forced failure of an expansion causes Exim to
27901 behave as if the relevant option were unset.
27903 .vindex &$tls_out_bits$&
27904 .vindex &$tls_out_cipher$&
27905 .vindex &$tls_out_peerdn$&
27906 .vindex &$tls_out_sni$&
27907 Before an SMTP connection is established, the
27908 &$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$&
27909 variables are emptied. (Until the first connection, they contain the values
27910 that were set when the message was received.) If STARTTLS is subsequently
27911 successfully obeyed, these variables are set to the relevant values for the
27912 outgoing connection.
27916 .section "Use of TLS Server Name Indication" "SECTtlssni"
27917 .cindex "TLS" "Server Name Indication"
27918 .vindex "&$tls_in_sni$&"
27919 .oindex "&%tls_in_sni%&"
27920 With TLS1.0 or above, there is an extension mechanism by which extra
27921 information can be included at various points in the protocol. One of these
27922 extensions, documented in RFC 6066 (and before that RFC 4366) is
27923 &"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the
27924 client in the initial handshake, so that the server can examine the servername
27925 within and possibly choose to use different certificates and keys (and more)
27928 This is analogous to HTTP's &"Host:"& header, and is the main mechanism by
27929 which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP
27932 With SMTP to MX, there are the same problems here as in choosing the identity
27933 against which to validate a certificate: you can't rely on insecure DNS to
27934 provide the identity which you then cryptographically verify. So this will
27935 be of limited use in that environment.
27937 With SMTP to Submission, there is a well-defined hostname which clients are
27938 connecting to and can validate certificates against. Thus clients &*can*&
27939 choose to include this information in the TLS negotiation. If this becomes
27940 wide-spread, then hosters can choose to present different certificates to
27941 different clients. Or even negotiate different cipher suites.
27943 The &%tls_sni%& option on an SMTP transport is an expanded string; the result,
27944 if not empty, will be sent on a TLS session as part of the handshake. There's
27945 nothing more to it. Choosing a sensible value not derived insecurely is the
27946 only point of caution. The &$tls_out_sni$& variable will be set to this string
27947 for the lifetime of the client connection (including during authentication).
27949 Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
27950 received from a client.
27951 It can be logged with the &%log_selector%& item &`+tls_sni`&.
27953 If the string &`tls_in_sni`& appears in the main section's &%tls_certificate%&
27954 option (prior to expansion) then the following options will be re-expanded
27955 during TLS session handshake, to permit alternative values to be chosen:
27958 &%tls_certificate%&
27964 &%tls_verify_certificates%&
27969 Great care should be taken to deal with matters of case, various injection
27970 attacks in the string (&`../`& or SQL), and ensuring that a valid filename
27971 can always be referenced; it is important to remember that &$tls_in_sni$& is
27972 arbitrary unverified data provided prior to authentication.
27973 Further, the initial certificate is loaded before SNI is arrived, so
27974 an expansion for &%tls_certificate%& must have a default which is used
27975 when &$tls_in_sni$& is empty.
27977 The Exim developers are proceeding cautiously and so far no other TLS options
27980 When Exim is built against OpenSSL, OpenSSL must have been built with support
27981 for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with
27982 enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and
27983 see &`-servername`& in the output, then OpenSSL has support.
27985 When Exim is built against GnuTLS, SNI support is available as of GnuTLS
27986 0.5.10. (Its presence predates the current API which Exim uses, so if Exim
27987 built, then you have SNI support).
27991 .section "Multiple messages on the same encrypted TCP/IP connection" &&&
27993 .cindex "multiple SMTP deliveries with TLS"
27994 .cindex "TLS" "multiple message deliveries"
27995 Exim sends multiple messages down the same TCP/IP connection by starting up
27996 an entirely new delivery process for each message, passing the socket from
27997 one process to the next. This implementation does not fit well with the use
27998 of TLS, because there is quite a lot of state information associated with a TLS
27999 connection, not just a socket identification. Passing all the state information
28000 to a new process is not feasible. Consequently, for sending using TLS Exim
28001 starts an additional proxy process for handling the encryption, piping the
28002 unencrypted data stream from and to the delivery processes.
28004 An older mode of operation can be enabled on a per-host basis by the
28005 &%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
28006 this list the proxy process described above is not used; instead Exim
28007 shuts down an existing TLS session being run by the delivery process
28008 before passing the socket to a new process. The new process may then
28009 try to start a new TLS session, and if successful, may try to re-authenticate
28010 if AUTH is in use, before sending the next message.
28012 The RFC is not clear as to whether or not an SMTP session continues in clear
28013 after TLS has been shut down, or whether TLS may be restarted again later, as
28014 just described. However, if the server is Exim, this shutdown and
28015 reinitialization works. It is not known which (if any) other servers operate
28016 successfully if the client closes a TLS session and continues with unencrypted
28017 SMTP, but there are certainly some that do not work. For such servers, Exim
28018 should not pass the socket to another process, because the failure of the
28019 subsequent attempt to use it would cause Exim to record a temporary host error,
28020 and delay other deliveries to that host.
28022 To test for this case, Exim sends an EHLO command to the server after
28023 closing down the TLS session. If this fails in any way, the connection is
28024 closed instead of being passed to a new delivery process, but no retry
28025 information is recorded.
28027 There is also a manual override; you can set &%hosts_nopass_tls%& on the
28028 &(smtp)& transport to match those hosts for which Exim should not pass
28029 connections to new processes if TLS has been used.
28034 .section "Certificates and all that" "SECTcerandall"
28035 .cindex "certificate" "references to discussion"
28036 In order to understand fully how TLS works, you need to know about
28037 certificates, certificate signing, and certificate authorities. This is not the
28038 place to give a tutorial, especially as I do not know very much about it
28039 myself. Some helpful introduction can be found in the FAQ for the SSL addition
28040 to Apache, currently at
28042 &url(http://www.modssl.org/docs/2.7/ssl_faq.html#ToC24)
28044 Other parts of the &'modssl'& documentation are also helpful, and have
28045 links to further files.
28046 Eric Rescorla's book, &'SSL and TLS'&, published by Addison-Wesley (ISBN
28047 0-201-61598-3), contains both introductory and more in-depth descriptions.
28048 Some sample programs taken from the book are available from
28050 &url(http://www.rtfm.com/openssl-examples/)
28054 .section "Certificate chains" "SECID186"
28055 The file named by &%tls_certificate%& may contain more than one
28056 certificate. This is useful in the case where the certificate that is being
28057 sent is validated by an intermediate certificate which the other end does
28058 not have. Multiple certificates must be in the correct order in the file.
28059 First the host's certificate itself, then the first intermediate
28060 certificate to validate the issuer of the host certificate, then the next
28061 intermediate certificate to validate the issuer of the first intermediate
28062 certificate, and so on, until finally (optionally) the root certificate.
28063 The root certificate must already be trusted by the recipient for
28064 validation to succeed, of course, but if it's not preinstalled, sending the
28065 root certificate along with the rest makes it available for the user to
28066 install if the receiving end is a client MUA that can interact with a user.
28068 Note that certificates using MD5 are unlikely to work on today's Internet;
28069 even if your libraries allow loading them for use in Exim when acting as a
28070 server, increasingly clients will not accept such certificates. The error
28071 diagnostics in such a case can be frustratingly vague.
28075 .section "Self-signed certificates" "SECID187"
28076 .cindex "certificate" "self-signed"
28077 You can create a self-signed certificate using the &'req'& command provided
28078 with OpenSSL, like this:
28079 . ==== Do not shorten the duration here without reading and considering
28080 . ==== the text below. Please leave it at 9999 days.
28082 openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \
28085 &_file1_& and &_file2_& can be the same file; the key and the certificate are
28086 delimited and so can be identified independently. The &%-days%& option
28087 specifies a period for which the certificate is valid. The &%-nodes%& option is
28088 important: if you do not set it, the key is encrypted with a passphrase
28089 that you are prompted for, and any use that is made of the key causes more
28090 prompting for the passphrase. This is not helpful if you are going to use
28091 this certificate and key in an MTA, where prompting is not possible.
28093 . ==== I expect to still be working 26 years from now. The less technical
28094 . ==== debt I create, in terms of storing up trouble for my later years, the
28095 . ==== happier I will be then. We really have reached the point where we
28096 . ==== should start, at the very least, provoking thought and making folks
28097 . ==== pause before proceeding, instead of leaving all the fixes until two
28098 . ==== years before 2^31 seconds after the 1970 Unix epoch.
28100 NB: we are now past the point where 9999 days takes us past the 32-bit Unix
28101 epoch. If your system uses unsigned time_t (most do) and is 32-bit, then
28102 the above command might produce a date in the past. Think carefully about
28103 the lifetime of the systems you're deploying, and either reduce the duration
28104 of the certificate or reconsider your platform deployment. (At time of
28105 writing, reducing the duration is the most likely choice, but the inexorable
28106 progression of time takes us steadily towards an era where this will not
28107 be a sensible resolution).
28109 A self-signed certificate made in this way is sufficient for testing, and
28110 may be adequate for all your requirements if you are mainly interested in
28111 encrypting transfers, and not in secure identification.
28113 However, many clients require that the certificate presented by the server be a
28114 user (also called &"leaf"& or &"site"&) certificate, and not a self-signed
28115 certificate. In this situation, the self-signed certificate described above
28116 must be installed on the client host as a trusted root &'certification
28117 authority'& (CA), and the certificate used by Exim must be a user certificate
28118 signed with that self-signed certificate.
28120 For information on creating self-signed CA certificates and using them to sign
28121 user certificates, see the &'General implementation overview'& chapter of the
28122 Open-source PKI book, available online at
28123 &url(http://ospkibook.sourceforge.net/).
28124 .ecindex IIDencsmtp1
28125 .ecindex IIDencsmtp2
28129 .section DANE "SECDANE"
28131 DNS-based Authentication of Named Entities, as applied to SMTP over TLS, provides assurance to a client that
28132 it is actually talking to the server it wants to rather than some attacker operating a Man In The Middle (MITM)
28133 operation. The latter can terminate the TLS connection you make, and make another one to the server (so both
28134 you and the server still think you have an encrypted connection) and, if one of the "well known" set of
28135 Certificate Authorities has been suborned - something which *has* been seen already (2014), a verifiable
28136 certificate (if you're using normal root CAs, eg. the Mozilla set, as your trust anchors).
28138 What DANE does is replace the CAs with the DNS as the trust anchor. The assurance is limited to a) the possibility
28139 that the DNS has been suborned, b) mistakes made by the admins of the target server. The attack surface presented
28140 by (a) is thought to be smaller than that of the set of root CAs.
28142 It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
28143 fail to pass on a server's STARTTLS.
28145 DANE scales better than having to maintain (and side-channel communicate) copies of server certificates
28146 for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
28147 client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
28149 DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients
28150 that DNS lookups they do for the server have not been tampered with. The domain MX record applying
28151 to this server, its A record, its TLSA record and any associated CNAME records must all be covered by
28153 2) add TLSA DNS records. These say what the server certificate for a TLS connection should be.
28154 3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records.
28156 There are no changes to Exim specific to server-side operation of DANE.
28157 Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes
28158 in &_Local/Makefile_&.
28159 If it has been included, the macro "_HAVE_DANE" will be defined.
28161 The TLSA record for the server may have "certificate usage" of DANE-TA(2) or DANE-EE(3). The latter specifies
28162 the End Entity directly, i.e. the certificate involved is that of the server (and should be the sole one transmitted
28163 during the TLS handshake); this is appropriate for a single system, using a self-signed certificate.
28164 DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public,
28165 well-known one. A private CA at simplest is just a self-signed certificate which is used to sign
28166 cerver certificates, but running one securely does require careful arrangement. If a private CA is used
28167 then either all clients must be primed with it, or (probably simpler) the server TLS handshake must transmit
28168 the entire certificate chain from CA to server-certificate. If a public CA is used then all clients must be primed with it
28169 (losing one advantage of DANE) - but the attack surface is reduced from all public CAs to that single CA.
28170 DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record,
28171 all of which point to a single TLSA record.
28173 Another approach which should be seriously considered is to use DANE with a certificate
28174 from a public CA, because of another technology, "MTA-STS", described below.
28176 The TLSA record should have a Selector field of SPKI(1) and a Matching Type field of SHA2-512(2).
28178 At the time of writing, &url(https://www.huque.com/bin/gen_tlsa)
28179 is useful for quickly generating TLSA records; and commands like
28182 openssl x509 -in -pubkey -noout <certificate.pem \
28183 | openssl rsa -outform der -pubin 2>/dev/null \
28188 are workable for 4th-field hashes.
28190 For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName).
28192 The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise
28193 be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the
28194 default of requesting OCSP for all hosts is modified iff DANE is in use, to:
28197 hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \
28198 {= {4}{$tls_out_tlsa_usage}} } \
28202 The (new) variable &$tls_out_tlsa_usage$& is a bitfield with numbered bits set for TLSA record usage codes.
28203 The zero above means DANE was not in use, the four means that only DANE-TA usage TLSA records were
28204 found. If the definition of &%hosts_request_ocsp%& includes the
28205 string "tls_out_tlsa_usage", they are re-expanded in time to
28206 control the OCSP request.
28208 This modification of hosts_request_ocsp is only done if it has the default value of "*". Admins who change it, and
28209 those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings.
28212 For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%&
28213 and &%dane_require_tls_ciphers%&.
28214 The require variant will result in failure if the target host is not DNSSEC-secured.
28216 DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
28218 A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using dnssec.
28219 If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
28220 will be required for the host. If it does not, the host will not
28221 be used; there is no fallback to non-DANE or non-TLS.
28223 If DANE is requested and usable, then the TLS cipher list configuration
28224 prefers to use the option &%dane_require_tls_ciphers%& and falls
28225 back to &%tls_require_ciphers%& only if that is unset.
28226 This lets you configure "decent crypto" for DANE and "better than nothing
28227 crypto" as the default. Note though that while GnuTLS lets the string control
28228 which versions of TLS/SSL will be negotiated, OpenSSL does not and you're
28229 limited to ciphersuite constraints.
28231 If DANE is requested and useable (see above) the following transport options are ignored:
28235 tls_try_verify_hosts
28236 tls_verify_certificates
28238 tls_verify_cert_hostnames
28241 If DANE is not usable, whether requested or not, and CA-anchored
28242 verification evaluation is wanted, the above variables should be set appropriately.
28244 Currently the &%dnssec_request_domains%& must be active and &%dnssec_require_domains%& is ignored.
28246 If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane".
28248 There is a new variable &$tls_out_dane$& which will have "yes" if
28249 verification succeeded using DANE and "no" otherwise (only useful
28250 in combination with events; see &<<CHAPevents>>&),
28251 and a new variable &$tls_out_tlsa_usage$& (detailed above).
28253 .cindex DANE reporting
28254 An event (see &<<CHAPevents>>&) of type "dane:fail" will be raised on failures
28255 to achieve DANE-verified connection, if one was either requested and offered, or
28256 required. This is intended to support TLS-reporting as defined in
28257 &url(https://tools.ietf.org/html/draft-ietf-uta-smtp-tlsrpt-17).
28258 The &$event_data$& will be one of the Result Types defined in
28259 Section 4.3 of that document.
28261 Under GnuTLS, DANE is only supported from version 3.0.0 onwards.
28263 DANE is specified in published RFCs and decouples certificate authority trust
28264 selection from a "race to the bottom" of "you must trust everything for mail
28265 to get through". There is an alternative technology called MTA-STS, which
28266 instead publishes MX trust anchor information on an HTTPS website. At the
28267 time this text was last updated, MTA-STS was still a draft, not yet an RFC.
28268 Exim has no support for MTA-STS as a client, but Exim mail server operators
28269 can choose to publish information describing their TLS configuration using
28270 MTA-STS to let those clients who do use that protocol derive trust
28273 The MTA-STS design requires a certificate from a public Certificate Authority
28274 which is recognized by clients sending to you. That selection is outside your
28277 The most interoperable course of action is probably to use
28278 &url(https://letsencrypt.org/,Let's Encrypt), with automated certificate
28279 renewal; to publish the anchor information in DNSSEC-secured DNS via TLSA
28280 records for DANE clients (such as Exim and Postfix) and to publish anchor
28281 information for MTA-STS as well. This is what is done for the &'exim.org'&
28282 domain itself (with caveats around occasionally broken MTA-STS because of
28283 incompatible specification changes prior to reaching RFC status).
28287 . ////////////////////////////////////////////////////////////////////////////
28288 . ////////////////////////////////////////////////////////////////////////////
28290 .chapter "Access control lists" "CHAPACL"
28291 .scindex IIDacl "&ACL;" "description"
28292 .cindex "control of incoming mail"
28293 .cindex "message" "controlling incoming"
28294 .cindex "policy control" "access control lists"
28295 Access Control Lists (ACLs) are defined in a separate section of the run time
28296 configuration file, headed by &"begin acl"&. Each ACL definition starts with a
28297 name, terminated by a colon. Here is a complete ACL section that contains just
28298 one very small ACL:
28302 accept hosts = one.host.only
28304 You can have as many lists as you like in the ACL section, and the order in
28305 which they appear does not matter. The lists are self-terminating.
28307 The majority of ACLs are used to control Exim's behaviour when it receives
28308 certain SMTP commands. This applies both to incoming TCP/IP connections, and
28309 when a local process submits a message using SMTP by specifying the &%-bs%&
28310 option. The most common use is for controlling which recipients are accepted
28311 in incoming messages. In addition, you can define an ACL that is used to check
28312 local non-SMTP messages. The default configuration file contains an example of
28313 a realistic ACL for checking RCPT commands. This is discussed in chapter
28314 &<<CHAPdefconfil>>&.
28317 .section "Testing ACLs" "SECID188"
28318 The &%-bh%& command line option provides a way of testing your ACL
28319 configuration locally by running a fake SMTP session with which you interact.
28322 .section "Specifying when ACLs are used" "SECID189"
28323 .cindex "&ACL;" "options for specifying"
28324 In order to cause an ACL to be used, you have to name it in one of the relevant
28325 options in the main part of the configuration. These options are:
28326 .cindex "AUTH" "ACL for"
28327 .cindex "DATA" "ACLs for"
28328 .cindex "ETRN" "ACL for"
28329 .cindex "EXPN" "ACL for"
28330 .cindex "HELO" "ACL for"
28331 .cindex "EHLO" "ACL for"
28332 .cindex "DKIM" "ACL for"
28333 .cindex "MAIL" "ACL for"
28334 .cindex "QUIT, ACL for"
28335 .cindex "RCPT" "ACL for"
28336 .cindex "STARTTLS, ACL for"
28337 .cindex "VRFY" "ACL for"
28338 .cindex "SMTP" "connection, ACL for"
28339 .cindex "non-SMTP messages" "ACLs for"
28340 .cindex "MIME content scanning" "ACL for"
28341 .cindex "PRDR" "ACL for"
28344 .irow &%acl_not_smtp%& "ACL for non-SMTP messages"
28345 .irow &%acl_not_smtp_mime%& "ACL for non-SMTP MIME parts"
28346 .irow &%acl_not_smtp_start%& "ACL at start of non-SMTP message"
28347 .irow &%acl_smtp_auth%& "ACL for AUTH"
28348 .irow &%acl_smtp_connect%& "ACL for start of SMTP connection"
28349 .irow &%acl_smtp_data%& "ACL after DATA is complete"
28350 .irow &%acl_smtp_data_prdr%& "ACL for each recipient, after DATA is complete"
28351 .irow &%acl_smtp_dkim%& "ACL for each DKIM signer"
28352 .irow &%acl_smtp_etrn%& "ACL for ETRN"
28353 .irow &%acl_smtp_expn%& "ACL for EXPN"
28354 .irow &%acl_smtp_helo%& "ACL for HELO or EHLO"
28355 .irow &%acl_smtp_mail%& "ACL for MAIL"
28356 .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL"
28357 .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts"
28358 .irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations"
28359 .irow &%acl_smtp_predata%& "ACL at start of DATA command"
28360 .irow &%acl_smtp_quit%& "ACL for QUIT"
28361 .irow &%acl_smtp_rcpt%& "ACL for RCPT"
28362 .irow &%acl_smtp_starttls%& "ACL for STARTTLS"
28363 .irow &%acl_smtp_vrfy%& "ACL for VRFY"
28366 For example, if you set
28368 acl_smtp_rcpt = small_acl
28370 the little ACL defined above is used whenever Exim receives a RCPT command
28371 in an SMTP dialogue. The majority of policy tests on incoming messages can be
28372 done when RCPT commands arrive. A rejection of RCPT should cause the
28373 sending MTA to give up on the recipient address contained in the RCPT
28374 command, whereas rejection at other times may cause the client MTA to keep on
28375 trying to deliver the message. It is therefore recommended that you do as much
28376 testing as possible at RCPT time.
28379 .section "The non-SMTP ACLs" "SECID190"
28380 .cindex "non-SMTP messages" "ACLs for"
28381 The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they
28382 apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not
28383 really SMTP.) Many of the ACL conditions (for example, host tests, and tests on
28384 the state of the SMTP connection such as encryption and authentication) are not
28385 relevant and are forbidden in these ACLs. However, the sender and recipients
28386 are known, so the &%senders%& and &%sender_domains%& conditions and the
28387 &$sender_address$& and &$recipients$& variables can be used. Variables such as
28388 &$authenticated_sender$& are also available. You can specify added header lines
28389 in any of these ACLs.
28391 The &%acl_not_smtp_start%& ACL is run right at the start of receiving a
28392 non-SMTP message, before any of the message has been read. (This is the
28393 analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of
28394 batched SMTP input, it runs after the DATA command has been reached. The
28395 result of this ACL is ignored; it cannot be used to reject a message. If you
28396 really need to, you could set a value in an ACL variable here and reject based
28397 on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set
28398 controls, and in particular, it can be used to set
28400 control = suppress_local_fixups
28402 This cannot be used in the other non-SMTP ACLs because by the time they are
28403 run, it is too late.
28405 The &%acl_not_smtp_mime%& ACL is available only when Exim is compiled with the
28406 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
28408 The &%acl_not_smtp%& ACL is run just before the &[local_scan()]& function. Any
28409 kind of rejection is treated as permanent, because there is no way of sending a
28410 temporary error for these kinds of message.
28413 .section "The SMTP connect ACL" "SECID191"
28414 .cindex "SMTP" "connection, ACL for"
28415 .oindex &%smtp_banner%&
28416 The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP
28417 session, after the test specified by &%host_reject_connection%& (which is now
28418 an anomaly) and any TCP Wrappers testing (if configured). If the connection is
28419 accepted by an &%accept%& verb that has a &%message%& modifier, the contents of
28420 the message override the banner message that is otherwise specified by the
28421 &%smtp_banner%& option.
28424 .section "The EHLO/HELO ACL" "SECID192"
28425 .cindex "EHLO" "ACL for"
28426 .cindex "HELO" "ACL for"
28427 The ACL test specified by &%acl_smtp_helo%& happens when the client issues an
28428 EHLO or HELO command, after the tests specified by &%helo_accept_junk_hosts%&,
28429 &%helo_allow_chars%&, &%helo_verify_hosts%&, and &%helo_try_verify_hosts%&.
28430 Note that a client may issue more than one EHLO or HELO command in an SMTP
28431 session, and indeed is required to issue a new EHLO or HELO after successfully
28432 setting up encryption following a STARTTLS command.
28434 Note also that a deny neither forces the client to go away nor means that
28435 mail will be refused on the connection. Consider checking for
28436 &$sender_helo_name$& being defined in a MAIL or RCPT ACL to do that.
28438 If the command is accepted by an &%accept%& verb that has a &%message%&
28439 modifier, the message may not contain more than one line (it will be truncated
28440 at the first newline and a panic logged if it does). Such a message cannot
28441 affect the EHLO options that are listed on the second and subsequent lines of
28445 .section "The DATA ACLs" "SECID193"
28446 .cindex "DATA" "ACLs for"
28447 Two ACLs are associated with the DATA command, because it is two-stage
28448 command, with two responses being sent to the client.
28449 When the DATA command is received, the ACL defined by &%acl_smtp_predata%&
28450 is obeyed. This gives you control after all the RCPT commands, but before
28451 the message itself is received. It offers the opportunity to give a negative
28452 response to the DATA command before the data is transmitted. Header lines
28453 added by MAIL or RCPT ACLs are not visible at this time, but any that
28454 are defined here are visible when the &%acl_smtp_data%& ACL is run.
28456 You cannot test the contents of the message, for example, to verify addresses
28457 in the headers, at RCPT time or when the DATA command is received. Such
28458 tests have to appear in the ACL that is run after the message itself has been
28459 received, before the final response to the DATA command is sent. This is
28460 the ACL specified by &%acl_smtp_data%&, which is the second ACL that is
28461 associated with the DATA command.
28463 .cindex CHUNKING "BDAT command"
28464 .cindex BDAT "SMTP command"
28465 .cindex "RFC 3030" CHUNKING
28466 If CHUNKING was advertised and a BDAT command sequence is received,
28467 the &%acl_smtp_predata%& ACL is not run.
28468 . XXX why not? It should be possible, for the first BDAT.
28469 The &%acl_smtp_data%& is run after the last BDAT command and all of
28470 the data specified is received.
28472 For both of these ACLs, it is not possible to reject individual recipients. An
28473 error response rejects the entire message. Unfortunately, it is known that some
28474 MTAs do not treat hard (5&'xx'&) responses to the DATA command (either
28475 before or after the data) correctly &-- they keep the message on their queues
28476 and try again later, but that is their problem, though it does waste some of
28479 The &%acl_smtp_data%& ACL is run after
28480 the &%acl_smtp_data_prdr%&,
28481 the &%acl_smtp_dkim%&
28482 and the &%acl_smtp_mime%& ACLs.
28484 .section "The SMTP DKIM ACL" "SECTDKIMACL"
28485 The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support
28486 enabled (which is the default).
28488 The ACL test specified by &%acl_smtp_dkim%& happens after a message has been
28489 received, and is executed for each DKIM signature found in a message. If not
28490 otherwise specified, the default action is to accept.
28492 This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&.
28494 For details on the operation of DKIM, see section &<<SECDKIM>>&.
28497 .section "The SMTP MIME ACL" "SECID194"
28498 The &%acl_smtp_mime%& option is available only when Exim is compiled with the
28499 content-scanning extension. For details, see chapter &<<CHAPexiscan>>&.
28501 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
28504 .section "The SMTP PRDR ACL" "SECTPRDRACL"
28505 .cindex "PRDR" "ACL for"
28506 .oindex "&%prdr_enable%&"
28507 The &%acl_smtp_data_prdr%& ACL is available only when Exim is compiled
28508 with PRDR support enabled (which is the default).
28509 It becomes active only when the PRDR feature is negotiated between
28510 client and server for a message, and more than one recipient
28513 The ACL test specified by &%acl_smtp_data_prdr%& happens after a message
28514 has been received, and is executed once for each recipient of the message
28515 with &$local_part$& and &$domain$& valid.
28516 The test may accept, defer or deny for individual recipients.
28517 The &%acl_smtp_data%& will still be called after this ACL and
28518 can reject the message overall, even if this ACL has accepted it
28519 for some or all recipients.
28521 PRDR may be used to support per-user content filtering. Without it
28522 one must defer any recipient after the first that has a different
28523 content-filter configuration. With PRDR, the RCPT-time check
28524 .cindex "PRDR" "variable for"
28525 for this can be disabled when the variable &$prdr_requested$&
28527 Any required difference in behaviour of the main DATA-time
28528 ACL should however depend on the PRDR-time ACL having run, as Exim
28529 will avoid doing so in some situations (e.g. single-recipient mails).
28531 See also the &%prdr_enable%& global option
28532 and the &%hosts_try_prdr%& smtp transport option.
28534 This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&.
28535 If the ACL is not defined, processing completes as if
28536 the feature was not requested by the client.
28538 .section "The QUIT ACL" "SECTQUITACL"
28539 .cindex "QUIT, ACL for"
28540 The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL
28541 does not affect the response code to QUIT, which is always 221. Thus, the ACL
28542 does not in fact control any access.
28543 For this reason, it may only accept
28544 or warn as its final result.
28546 This ACL can be used for tasks such as custom logging at the end of an SMTP
28547 session. For example, you can use ACL variables in other ACLs to count
28548 messages, recipients, etc., and log the totals at QUIT time using one or
28549 more &%logwrite%& modifiers on a &%warn%& verb.
28551 &*Warning*&: Only the &$acl_c$&&'x'& variables can be used for this, because
28552 the &$acl_m$&&'x'& variables are reset at the end of each incoming message.
28554 You do not need to have a final &%accept%&, but if you do, you can use a
28555 &%message%& modifier to specify custom text that is sent as part of the 221
28558 This ACL is run only for a &"normal"& QUIT. For certain kinds of disastrous
28559 failure (for example, failure to open a log file, or when Exim is bombing out
28560 because it has detected an unrecoverable error), all SMTP commands from the
28561 client are given temporary error responses until QUIT is received or the
28562 connection is closed. In these special cases, the QUIT ACL does not run.
28565 .section "The not-QUIT ACL" "SECTNOTQUITACL"
28566 .vindex &$acl_smtp_notquit$&
28567 The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when
28568 an SMTP session ends without sending QUIT. However, when Exim itself is in bad
28569 trouble, such as being unable to write to its log files, this ACL is not run,
28570 because it might try to do things (such as write to log files) that make the
28571 situation even worse.
28573 Like the QUIT ACL, this ACL is provided to make it possible to do customized
28574 logging or to gather statistics, and its outcome is ignored. The &%delay%&
28575 modifier is forbidden in this ACL, and the only permitted verbs are &%accept%&
28578 .vindex &$smtp_notquit_reason$&
28579 When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set
28580 to a string that indicates the reason for the termination of the SMTP
28581 connection. The possible values are:
28583 .irow &`acl-drop`& "Another ACL issued a &%drop%& command"
28584 .irow &`bad-commands`& "Too many unknown or non-mail commands"
28585 .irow &`command-timeout`& "Timeout while reading SMTP commands"
28586 .irow &`connection-lost`& "The SMTP connection has been lost"
28587 .irow &`data-timeout`& "Timeout while reading message data"
28588 .irow &`local-scan-error`& "The &[local_scan()]& function crashed"
28589 .irow &`local-scan-timeout`& "The &[local_scan()]& function timed out"
28590 .irow &`signal-exit`& "SIGTERM or SIGINT"
28591 .irow &`synchronization-error`& "SMTP synchronization error"
28592 .irow &`tls-failed`& "TLS failed to start"
28594 In most cases when an SMTP connection is closed without having received QUIT,
28595 Exim sends an SMTP response message before actually closing the connection.
28596 With the exception of the &`acl-drop`& case, the default message can be
28597 overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a
28598 &%drop%& verb in another ACL, it is the message from the other ACL that is
28602 .section "Finding an ACL to use" "SECID195"
28603 .cindex "&ACL;" "finding which to use"
28604 The value of an &%acl_smtp_%&&'xxx'& option is expanded before use, so
28605 you can use different ACLs in different circumstances. For example,
28607 acl_smtp_rcpt = ${if ={25}{$interface_port} \
28608 {acl_check_rcpt} {acl_check_rcpt_submit} }
28610 In the default configuration file there are some example settings for
28611 providing an RFC 4409 message &"submission"& service on port 587 and
28612 an RFC 8314 &"submissions"& service on port 465. You can use a string
28613 expansion like this to choose an ACL for MUAs on these ports which is
28614 more appropriate for this purpose than the default ACL on port 25.
28616 The expanded string does not have to be the name of an ACL in the
28617 configuration file; there are other possibilities. Having expanded the
28618 string, Exim searches for an ACL as follows:
28621 If the string begins with a slash, Exim uses it as a file name, and reads its
28622 contents as an ACL. The lines are processed in the same way as lines in the
28623 Exim configuration file. In particular, continuation lines are supported, blank
28624 lines are ignored, as are lines whose first non-whitespace character is &"#"&.
28625 If the file does not exist or cannot be read, an error occurs (typically
28626 causing a temporary failure of whatever caused the ACL to be run). For example:
28628 acl_smtp_data = /etc/acls/\
28629 ${lookup{$sender_host_address}lsearch\
28630 {/etc/acllist}{$value}{default}}
28632 This looks up an ACL file to use on the basis of the host's IP address, falling
28633 back to a default if the lookup fails. If an ACL is successfully read from a
28634 file, it is retained in memory for the duration of the Exim process, so that it
28635 can be re-used without having to re-read the file.
28637 If the string does not start with a slash, and does not contain any spaces,
28638 Exim searches the ACL section of the configuration for an ACL whose name
28639 matches the string.
28641 If no named ACL is found, or if the string contains spaces, Exim parses
28642 the string as an inline ACL. This can save typing in cases where you just
28643 want to have something like
28645 acl_smtp_vrfy = accept
28647 in order to allow free use of the VRFY command. Such a string may contain
28648 newlines; it is processed in the same way as an ACL that is read from a file.
28654 .section "ACL return codes" "SECID196"
28655 .cindex "&ACL;" "return codes"
28656 Except for the QUIT ACL, which does not affect the SMTP return code (see
28657 section &<<SECTQUITACL>>& above), the result of running an ACL is either
28658 &"accept"& or &"deny"&, or, if some test cannot be completed (for example, if a
28659 database is down), &"defer"&. These results cause 2&'xx'&, 5&'xx'&, and 4&'xx'&
28660 return codes, respectively, to be used in the SMTP dialogue. A fourth return,
28661 &"error"&, occurs when there is an error such as invalid syntax in the ACL.
28662 This also causes a 4&'xx'& return code.
28664 For the non-SMTP ACL, &"defer"& and &"error"& are treated in the same way as
28665 &"deny"&, because there is no mechanism for passing temporary errors to the
28666 submitters of non-SMTP messages.
28669 ACLs that are relevant to message reception may also return &"discard"&. This
28670 has the effect of &"accept"&, but causes either the entire message or an
28671 individual recipient address to be discarded. In other words, it is a
28672 blackholing facility. Use it with care.
28674 If the ACL for MAIL returns &"discard"&, all recipients are discarded, and no
28675 ACL is run for subsequent RCPT commands. The effect of &"discard"& in a
28676 RCPT ACL is to discard just the one recipient address. If there are no
28677 recipients left when the message's data is received, the DATA ACL is not
28678 run. A &"discard"& return from the DATA or the non-SMTP ACL discards all the
28679 remaining recipients. The &"discard"& return is not permitted for the
28680 &%acl_smtp_predata%& ACL.
28682 If the ACL for VRFY returns &"accept"&, a recipient verify (without callout)
28683 is done on the address and the result determines the SMTP response.
28686 .cindex "&[local_scan()]& function" "when all recipients discarded"
28687 The &[local_scan()]& function is always run, even if there are no remaining
28688 recipients; it may create new recipients.
28692 .section "Unset ACL options" "SECID197"
28693 .cindex "&ACL;" "unset options"
28694 The default actions when any of the &%acl_%&&'xxx'& options are unset are not
28695 all the same. &*Note*&: These defaults apply only when the relevant ACL is
28696 not defined at all. For any defined ACL, the default action when control
28697 reaches the end of the ACL statements is &"deny"&.
28699 For &%acl_smtp_quit%& and &%acl_not_smtp_start%& there is no default because
28700 these two are ACLs that are used only for their side effects. They cannot be
28701 used to accept or reject anything.
28703 For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&,
28704 &%acl_smtp_data%&, &%acl_smtp_helo%&, &%acl_smtp_mail%&, &%acl_smtp_mailauth%&,
28705 &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action
28706 when the ACL is not defined is &"accept"&.
28708 For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and
28709 &%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&.
28710 This means that &%acl_smtp_rcpt%& must be defined in order to receive any
28711 messages over an SMTP connection. For an example, see the ACL in the default
28712 configuration file.
28717 .section "Data for message ACLs" "SECID198"
28718 .cindex "&ACL;" "data for message ACL"
28720 .vindex &$local_part$&
28721 .vindex &$sender_address$&
28722 .vindex &$sender_host_address$&
28723 .vindex &$smtp_command$&
28724 When a MAIL or RCPT ACL, or either of the DATA ACLs, is running, the variables
28725 that contain information about the host and the message's sender (for example,
28726 &$sender_host_address$& and &$sender_address$&) are set, and can be used in ACL
28727 statements. In the case of RCPT (but not MAIL or DATA), &$domain$& and
28728 &$local_part$& are set from the argument address. The entire SMTP command
28729 is available in &$smtp_command$&.
28731 When an ACL for the AUTH parameter of MAIL is running, the variables that
28732 contain information about the host are set, but &$sender_address$& is not yet
28733 set. Section &<<SECTauthparamail>>& contains a discussion of this parameter and
28736 .vindex "&$message_size$&"
28737 The &$message_size$& variable is set to the value of the SIZE parameter on
28738 the MAIL command at MAIL, RCPT and pre-data time, or to -1 if
28739 that parameter is not given. The value is updated to the true message size by
28740 the time the final DATA ACL is run (after the message data has been
28743 .vindex "&$rcpt_count$&"
28744 .vindex "&$recipients_count$&"
28745 The &$rcpt_count$& variable increases by one for each RCPT command received.
28746 The &$recipients_count$& variable increases by one each time a RCPT command is
28747 accepted, so while an ACL for RCPT is being processed, it contains the number
28748 of previously accepted recipients. At DATA time (for both the DATA ACLs),
28749 &$rcpt_count$& contains the total number of RCPT commands, and
28750 &$recipients_count$& contains the total number of accepted recipients.
28756 .section "Data for non-message ACLs" "SECTdatfornon"
28757 .cindex "&ACL;" "data for non-message ACL"
28758 .vindex &$smtp_command_argument$&
28759 .vindex &$smtp_command$&
28760 When an ACL is being run for AUTH, EHLO, ETRN, EXPN, HELO, STARTTLS, or VRFY,
28761 the remainder of the SMTP command line is placed in &$smtp_command_argument$&,
28762 and the entire SMTP command is available in &$smtp_command$&.
28763 These variables can be tested using a &%condition%& condition. For example,
28764 here is an ACL for use with AUTH, which insists that either the session is
28765 encrypted, or the CRAM-MD5 authentication method is used. In other words, it
28766 does not permit authentication methods that use cleartext passwords on
28767 unencrypted connections.
28770 accept encrypted = *
28771 accept condition = ${if eq{${uc:$smtp_command_argument}}\
28773 deny message = TLS encryption or CRAM-MD5 required
28775 (Another way of applying this restriction is to arrange for the authenticators
28776 that use cleartext passwords not to be advertised when the connection is not
28777 encrypted. You can use the generic &%server_advertise_condition%& authenticator
28778 option to do this.)
28782 .section "Format of an ACL" "SECID199"
28783 .cindex "&ACL;" "format of"
28784 .cindex "&ACL;" "verbs, definition of"
28785 An individual ACL consists of a number of statements. Each statement starts
28786 with a verb, optionally followed by a number of conditions and &"modifiers"&.
28787 Modifiers can change the way the verb operates, define error and log messages,
28788 set variables, insert delays, and vary the processing of accepted messages.
28790 If all the conditions are met, the verb is obeyed. The same condition may be
28791 used (with different arguments) more than once in the same statement. This
28792 provides a means of specifying an &"and"& conjunction between conditions. For
28795 deny dnslists = list1.example
28796 dnslists = list2.example
28798 If there are no conditions, the verb is always obeyed. Exim stops evaluating
28799 the conditions and modifiers when it reaches a condition that fails. What
28800 happens then depends on the verb (and in one case, on a special modifier). Not
28801 all the conditions make sense at every testing point. For example, you cannot
28802 test a sender address in the ACL that is run for a VRFY command.
28805 .section "ACL verbs" "SECID200"
28806 The ACL verbs are as follows:
28809 .cindex "&%accept%& ACL verb"
28810 &%accept%&: If all the conditions are met, the ACL returns &"accept"&. If any
28811 of the conditions are not met, what happens depends on whether &%endpass%&
28812 appears among the conditions (for syntax see below). If the failing condition
28813 is before &%endpass%&, control is passed to the next ACL statement; if it is
28814 after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to
28815 check a RCPT command:
28817 accept domains = +local_domains
28821 If the recipient domain does not match the &%domains%& condition, control
28822 passes to the next statement. If it does match, the recipient is verified, and
28823 the command is accepted if verification succeeds. However, if verification
28824 fails, the ACL yields &"deny"&, because the failing condition is after
28827 The &%endpass%& feature has turned out to be confusing to many people, so its
28828 use is not recommended nowadays. It is always possible to rewrite an ACL so
28829 that &%endpass%& is not needed, and it is no longer used in the default
28832 .cindex "&%message%& ACL modifier" "with &%accept%&"
28833 If a &%message%& modifier appears on an &%accept%& statement, its action
28834 depends on whether or not &%endpass%& is present. In the absence of &%endpass%&
28835 (when an &%accept%& verb either accepts or passes control to the next
28836 statement), &%message%& can be used to vary the message that is sent when an
28837 SMTP command is accepted. For example, in a RCPT ACL you could have:
28839 &`accept `&<&'some conditions'&>
28840 &` message = OK, I will allow you through today`&
28842 You can specify an SMTP response code, optionally followed by an &"extended
28843 response code"& at the start of the message, but the first digit must be the
28844 same as would be sent by default, which is 2 for an &%accept%& verb.
28846 If &%endpass%& is present in an &%accept%& statement, &%message%& specifies
28847 an error message that is used when access is denied. This behaviour is retained
28848 for backward compatibility, but current &"best practice"& is to avoid the use
28853 .cindex "&%defer%& ACL verb"
28854 &%defer%&: If all the conditions are true, the ACL returns &"defer"& which, in
28855 an SMTP session, causes a 4&'xx'& response to be given. For a non-SMTP ACL,
28856 &%defer%& is the same as &%deny%&, because there is no way of sending a
28857 temporary error. For a RCPT command, &%defer%& is much the same as using a
28858 &(redirect)& router and &`:defer:`& while verifying, but the &%defer%& verb can
28859 be used in any ACL, and even for a recipient it might be a simpler approach.
28863 .cindex "&%deny%& ACL verb"
28864 &%deny%&: If all the conditions are met, the ACL returns &"deny"&. If any of
28865 the conditions are not met, control is passed to the next ACL statement. For
28868 deny dnslists = blackholes.mail-abuse.org
28870 rejects commands from hosts that are on a DNS black list.
28874 .cindex "&%discard%& ACL verb"
28875 &%discard%&: This verb behaves like &%accept%&, except that it returns
28876 &"discard"& from the ACL instead of &"accept"&. It is permitted only on ACLs
28877 that are concerned with receiving messages. When all the conditions are true,
28878 the sending entity receives a &"success"& response. However, &%discard%& causes
28879 recipients to be discarded. If it is used in an ACL for RCPT, just the one
28880 recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the
28881 message's recipients are discarded. Recipients that are discarded before DATA
28882 do not appear in the log line when the &%received_recipients%& log selector is set.
28884 If the &%log_message%& modifier is set when &%discard%& operates,
28885 its contents are added to the line that is automatically written to the log.
28886 The &%message%& modifier operates exactly as it does for &%accept%&.
28890 .cindex "&%drop%& ACL verb"
28891 &%drop%&: This verb behaves like &%deny%&, except that an SMTP connection is
28892 forcibly closed after the 5&'xx'& error message has been sent. For example:
28894 drop message = I don't take more than 20 RCPTs
28895 condition = ${if > {$rcpt_count}{20}}
28897 There is no difference between &%deny%& and &%drop%& for the connect-time ACL.
28898 The connection is always dropped after sending a 550 response.
28901 .cindex "&%require%& ACL verb"
28902 &%require%&: If all the conditions are met, control is passed to the next ACL
28903 statement. If any of the conditions are not met, the ACL returns &"deny"&. For
28904 example, when checking a RCPT command,
28906 require message = Sender did not verify
28909 passes control to subsequent statements only if the message's sender can be
28910 verified. Otherwise, it rejects the command. Note the positioning of the
28911 &%message%& modifier, before the &%verify%& condition. The reason for this is
28912 discussed in section &<<SECTcondmodproc>>&.
28915 .cindex "&%warn%& ACL verb"
28916 &%warn%&: If all the conditions are true, a line specified by the
28917 &%log_message%& modifier is written to Exim's main log. Control always passes
28918 to the next ACL statement. If any condition is false, the log line is not
28919 written. If an identical log line is requested several times in the same
28920 message, only one copy is actually written to the log. If you want to force
28921 duplicates to be written, use the &%logwrite%& modifier instead.
28923 If &%log_message%& is not present, a &%warn%& verb just checks its conditions
28924 and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&,
28925 &%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the
28926 first failing condition. There is more about adding header lines in section
28927 &<<SECTaddheadacl>>&.
28929 If any condition on a &%warn%& statement cannot be completed (that is, there is
28930 some sort of defer), the log line specified by &%log_message%& is not written.
28931 This does not include the case of a forced failure from a lookup, which
28932 is considered to be a successful completion. After a defer, no further
28933 conditions or modifiers in the &%warn%& statement are processed. The incident
28934 is logged, and the ACL continues to be processed, from the next statement
28938 .vindex "&$acl_verify_message$&"
28939 When one of the &%warn%& conditions is an address verification that fails, the
28940 text of the verification failure message is in &$acl_verify_message$&. If you
28941 want this logged, you must set it up explicitly. For example:
28943 warn !verify = sender
28944 log_message = sender verify failed: $acl_verify_message
28948 At the end of each ACL there is an implicit unconditional &%deny%&.
28950 As you can see from the examples above, the conditions and modifiers are
28951 written one to a line, with the first one on the same line as the verb, and
28952 subsequent ones on following lines. If you have a very long condition, you can
28953 continue it onto several physical lines by the usual backslash continuation
28954 mechanism. It is conventional to align the conditions vertically.
28958 .section "ACL variables" "SECTaclvariables"
28959 .cindex "&ACL;" "variables"
28960 There are some special variables that can be set during ACL processing. They
28961 can be used to pass information between different ACLs, different invocations
28962 of the same ACL in the same SMTP connection, and between ACLs and the routers,
28963 transports, and filters that are used to deliver a message. The names of these
28964 variables must begin with &$acl_c$& or &$acl_m$&, followed either by a digit or
28965 an underscore, but the remainder of the name can be any sequence of
28966 alphanumeric characters and underscores that you choose. There is no limit on
28967 the number of ACL variables. The two sets act as follows:
28969 The values of those variables whose names begin with &$acl_c$& persist
28970 throughout an SMTP connection. They are never reset. Thus, a value that is set
28971 while receiving one message is still available when receiving the next message
28972 on the same SMTP connection.
28974 The values of those variables whose names begin with &$acl_m$& persist only
28975 while a message is being received. They are reset afterwards. They are also
28976 reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
28979 When a message is accepted, the current values of all the ACL variables are
28980 preserved with the message and are subsequently made available at delivery
28981 time. The ACL variables are set by a modifier called &%set%&. For example:
28983 accept hosts = whatever
28984 set acl_m4 = some value
28985 accept authenticated = *
28986 set acl_c_auth = yes
28988 &*Note*&: A leading dollar sign is not used when naming a variable that is to
28989 be set. If you want to set a variable without taking any action, you can use a
28990 &%warn%& verb without any other modifiers or conditions.
28992 .oindex &%strict_acl_vars%&
28993 What happens if a syntactically valid but undefined ACL variable is
28994 referenced depends on the setting of the &%strict_acl_vars%& option. If it is
28995 false (the default), an empty string is substituted; if it is true, an
28996 error is generated.
28998 Versions of Exim before 4.64 have a limited set of numbered variables, but
28999 their names are compatible, so there is no problem with upgrading.
29002 .section "Condition and modifier processing" "SECTcondmodproc"
29003 .cindex "&ACL;" "conditions; processing"
29004 .cindex "&ACL;" "modifiers; processing"
29005 An exclamation mark preceding a condition negates its result. For example:
29007 deny domains = *.dom.example
29008 !verify = recipient
29010 causes the ACL to return &"deny"& if the recipient domain ends in
29011 &'dom.example'& and the recipient address cannot be verified. Sometimes
29012 negation can be used on the right-hand side of a condition. For example, these
29013 two statements are equivalent:
29015 deny hosts = !192.168.3.4
29016 deny !hosts = 192.168.3.4
29018 However, for many conditions (&%verify%& being a good example), only left-hand
29019 side negation of the whole condition is possible.
29021 The arguments of conditions and modifiers are expanded. A forced failure
29022 of an expansion causes a condition to be ignored, that is, it behaves as if the
29023 condition is true. Consider these two statements:
29025 accept senders = ${lookup{$host_name}lsearch\
29026 {/some/file}{$value}fail}
29027 accept senders = ${lookup{$host_name}lsearch\
29028 {/some/file}{$value}{}}
29030 Each attempts to look up a list of acceptable senders. If the lookup succeeds,
29031 the returned list is searched, but if the lookup fails the behaviour is
29032 different in the two cases. The &%fail%& in the first statement causes the
29033 condition to be ignored, leaving no further conditions. The &%accept%& verb
29034 therefore succeeds. The second statement, however, generates an empty list when
29035 the lookup fails. No sender can match an empty list, so the condition fails,
29036 and therefore the &%accept%& also fails.
29038 ACL modifiers appear mixed in with conditions in ACL statements. Some of them
29039 specify actions that are taken as the conditions for a statement are checked;
29040 others specify text for messages that are used when access is denied or a
29041 warning is generated. The &%control%& modifier affects the way an incoming
29042 message is handled.
29044 The positioning of the modifiers in an ACL statement is important, because the
29045 processing of a verb ceases as soon as its outcome is known. Only those
29046 modifiers that have already been encountered will take effect. For example,
29047 consider this use of the &%message%& modifier:
29049 require message = Can't verify sender
29051 message = Can't verify recipient
29053 message = This message cannot be used
29055 If sender verification fails, Exim knows that the result of the statement is
29056 &"deny"&, so it goes no further. The first &%message%& modifier has been seen,
29057 so its text is used as the error message. If sender verification succeeds, but
29058 recipient verification fails, the second message is used. If recipient
29059 verification succeeds, the third message becomes &"current"&, but is never used
29060 because there are no more conditions to cause failure.
29062 For the &%deny%& verb, on the other hand, it is always the last &%message%&
29063 modifier that is used, because all the conditions must be true for rejection to
29064 happen. Specifying more than one &%message%& modifier does not make sense, and
29065 the message can even be specified after all the conditions. For example:
29068 !senders = *@my.domain.example
29069 message = Invalid sender from client host
29071 The &"deny"& result does not happen until the end of the statement is reached,
29072 by which time Exim has set up the message.
29076 .section "ACL modifiers" "SECTACLmodi"
29077 .cindex "&ACL;" "modifiers; list of"
29078 The ACL modifiers are as follows:
29081 .vitem &*add_header*&&~=&~<&'text'&>
29082 This modifier specifies one or more header lines that are to be added to an
29083 incoming message, assuming, of course, that the message is ultimately
29084 accepted. For details, see section &<<SECTaddheadacl>>&.
29086 .vitem &*continue*&&~=&~<&'text'&>
29087 .cindex "&%continue%& ACL modifier"
29088 .cindex "database" "updating in ACL"
29089 This modifier does nothing of itself, and processing of the ACL always
29090 continues with the next condition or modifier. The value of &%continue%& is in
29091 the side effects of expanding its argument. Typically this could be used to
29092 update a database. It is really just a syntactic tidiness, to avoid having to
29093 write rather ugly lines like this:
29095 &`condition = ${if eq{0}{`&<&'some expansion'&>&`}{true}{true}}`&
29097 Instead, all you need is
29099 &`continue = `&<&'some expansion'&>
29102 .vitem &*control*&&~=&~<&'text'&>
29103 .cindex "&%control%& ACL modifier"
29104 This modifier affects the subsequent processing of the SMTP connection or of an
29105 incoming message that is accepted. The effect of the first type of control
29106 lasts for the duration of the connection, whereas the effect of the second type
29107 lasts only until the current message has been received. The message-specific
29108 controls always apply to the whole message, not to individual recipients,
29109 even if the &%control%& modifier appears in a RCPT ACL.
29111 As there are now quite a few controls that can be applied, they are described
29112 separately in section &<<SECTcontrols>>&. The &%control%& modifier can be used
29113 in several different ways. For example:
29115 . ==== As this is a nested list, any displays it contains must be indented
29116 . ==== as otherwise they are too far to the left. That comment applies only
29117 . ==== when xmlto and fop are used; formatting with sdop gets it right either
29121 It can be at the end of an &%accept%& statement:
29123 accept ...some conditions
29124 control = queue_only
29126 In this case, the control is applied when this statement yields &"accept"&, in
29127 other words, when the conditions are all true.
29130 It can be in the middle of an &%accept%& statement:
29132 accept ...some conditions...
29133 control = queue_only
29134 ...some more conditions...
29136 If the first set of conditions are true, the control is applied, even if the
29137 statement does not accept because one of the second set of conditions is false.
29138 In this case, some subsequent statement must yield &"accept"& for the control
29142 It can be used with &%warn%& to apply the control, leaving the
29143 decision about accepting or denying to a subsequent verb. For
29146 warn ...some conditions...
29150 This example of &%warn%& does not contain &%message%&, &%log_message%&, or
29151 &%logwrite%&, so it does not add anything to the message and does not write a
29155 If you want to apply a control unconditionally, you can use it with a
29156 &%require%& verb. For example:
29158 require control = no_multiline_responses
29162 .vitem &*delay*&&~=&~<&'time'&>
29163 .cindex "&%delay%& ACL modifier"
29165 This modifier may appear in any ACL except notquit. It causes Exim to wait for
29166 the time interval before proceeding. However, when testing Exim using the
29167 &%-bh%& option, the delay is not actually imposed (an appropriate message is
29168 output instead). The time is given in the usual Exim notation, and the delay
29169 happens as soon as the modifier is processed. In an SMTP session, pending
29170 output is flushed before the delay is imposed.
29172 Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for
29175 deny ...some conditions...
29178 The delay happens if all the conditions are true, before the statement returns
29179 &"deny"&. Compare this with:
29182 ...some conditions...
29184 which waits for 30s before processing the conditions. The &%delay%& modifier
29185 can also be used with &%warn%& and together with &%control%&:
29187 warn ...some conditions...
29193 If &%delay%& is encountered when the SMTP PIPELINING extension is in use,
29194 responses to several commands are no longer buffered and sent in one packet (as
29195 they would normally be) because all output is flushed before imposing the
29196 delay. This optimization is disabled so that a number of small delays do not
29197 appear to the client as one large aggregated delay that might provoke an
29198 unwanted timeout. You can, however, disable output flushing for &%delay%& by
29199 using a &%control%& modifier to set &%no_delay_flush%&.
29203 .cindex "&%endpass%& ACL modifier"
29204 This modifier, which has no argument, is recognized only in &%accept%& and
29205 &%discard%& statements. It marks the boundary between the conditions whose
29206 failure causes control to pass to the next statement, and the conditions whose
29207 failure causes the ACL to return &"deny"&. This concept has proved to be
29208 confusing to some people, so the use of &%endpass%& is no longer recommended as
29209 &"best practice"&. See the description of &%accept%& above for more details.
29212 .vitem &*log_message*&&~=&~<&'text'&>
29213 .cindex "&%log_message%& ACL modifier"
29214 This modifier sets up a message that is used as part of the log message if the
29215 ACL denies access or a &%warn%& statement's conditions are true. For example:
29217 require log_message = wrong cipher suite $tls_in_cipher
29218 encrypted = DES-CBC3-SHA
29220 &%log_message%& is also used when recipients are discarded by &%discard%&. For
29223 &`discard `&<&'some conditions'&>
29224 &` log_message = Discarded $local_part@$domain because...`&
29226 When access is denied, &%log_message%& adds to any underlying error message
29227 that may exist because of a condition failure. For example, while verifying a
29228 recipient address, a &':fail:'& redirection might have already set up a
29231 The message may be defined before the conditions to which it applies, because
29232 the string expansion does not happen until Exim decides that access is to be
29233 denied. This means that any variables that are set by the condition are
29234 available for inclusion in the message. For example, the &$dnslist_$&<&'xxx'&>
29235 variables are set after a DNS black list lookup succeeds. If the expansion of
29236 &%log_message%& fails, or if the result is an empty string, the modifier is
29239 .vindex "&$acl_verify_message$&"
29240 If you want to use a &%warn%& statement to log the result of an address
29241 verification, you can use &$acl_verify_message$& to include the verification
29244 If &%log_message%& is used with a &%warn%& statement, &"Warning:"& is added to
29245 the start of the logged message. If the same warning log message is requested
29246 more than once while receiving a single email message, only one copy is
29247 actually logged. If you want to log multiple copies, use &%logwrite%& instead
29248 of &%log_message%&. In the absence of &%log_message%& and &%logwrite%&, nothing
29249 is logged for a successful &%warn%& statement.
29251 If &%log_message%& is not present and there is no underlying error message (for
29252 example, from the failure of address verification), but &%message%& is present,
29253 the &%message%& text is used for logging rejections. However, if any text for
29254 logging contains newlines, only the first line is logged. In the absence of
29255 both &%log_message%& and &%message%&, a default built-in message is used for
29256 logging rejections.
29259 .vitem "&*log_reject_target*&&~=&~<&'log name list'&>"
29260 .cindex "&%log_reject_target%& ACL modifier"
29261 .cindex "logging in ACL" "specifying which log"
29262 This modifier makes it possible to specify which logs are used for messages
29263 about ACL rejections. Its argument is a colon-separated list of words that can
29264 be &"main"&, &"reject"&, or &"panic"&. The default is &`main:reject`&. The list
29265 may be empty, in which case a rejection is not logged at all. For example, this
29266 ACL fragment writes no logging information when access is denied:
29268 &`deny `&<&'some conditions'&>
29269 &` log_reject_target =`&
29271 This modifier can be used in SMTP and non-SMTP ACLs. It applies to both
29272 permanent and temporary rejections. Its effect lasts for the rest of the
29276 .vitem &*logwrite*&&~=&~<&'text'&>
29277 .cindex "&%logwrite%& ACL modifier"
29278 .cindex "logging in ACL" "immediate"
29279 This modifier writes a message to a log file as soon as it is encountered when
29280 processing an ACL. (Compare &%log_message%&, which, except in the case of
29281 &%warn%& and &%discard%&, is used only if the ACL statement denies
29282 access.) The &%logwrite%& modifier can be used to log special incidents in
29285 &`accept `&<&'some special conditions'&>
29286 &` control = freeze`&
29287 &` logwrite = froze message because ...`&
29289 By default, the message is written to the main log. However, it may begin
29290 with a colon, followed by a comma-separated list of log names, and then
29291 another colon, to specify exactly which logs are to be written. For
29294 logwrite = :main,reject: text for main and reject logs
29295 logwrite = :panic: text for panic log only
29299 .vitem &*message*&&~=&~<&'text'&>
29300 .cindex "&%message%& ACL modifier"
29301 This modifier sets up a text string that is expanded and used as a response
29302 message when an ACL statement terminates the ACL with an &"accept"&, &"deny"&,
29303 or &"defer"& response. (In the case of the &%accept%& and &%discard%& verbs,
29304 there is some complication if &%endpass%& is involved; see the description of
29305 &%accept%& for details.)
29307 The expansion of the message happens at the time Exim decides that the ACL is
29308 to end, not at the time it processes &%message%&. If the expansion fails, or
29309 generates an empty string, the modifier is ignored. Here is an example where
29310 &%message%& must be specified first, because the ACL ends with a rejection if
29311 the &%hosts%& condition fails:
29313 require message = Host not recognized
29316 (Once a condition has failed, no further conditions or modifiers are
29319 .cindex "SMTP" "error codes"
29320 .oindex "&%smtp_banner%&
29321 For ACLs that are triggered by SMTP commands, the message is returned as part
29322 of the SMTP response. The use of &%message%& with &%accept%& (or &%discard%&)
29323 is meaningful only for SMTP, as no message is returned when a non-SMTP message
29324 is accepted. In the case of the connect ACL, accepting with a message modifier
29325 overrides the value of &%smtp_banner%&. For the EHLO/HELO ACL, a customized
29326 accept message may not contain more than one line (otherwise it will be
29327 truncated at the first newline and a panic logged), and it cannot affect the
29330 When SMTP is involved, the message may begin with an overriding response code,
29331 consisting of three digits optionally followed by an &"extended response code"&
29332 of the form &'n.n.n'&, each code being followed by a space. For example:
29334 deny message = 599 1.2.3 Host not welcome
29335 hosts = 192.168.34.0/24
29337 The first digit of the supplied response code must be the same as would be sent
29338 by default. A panic occurs if it is not. Exim uses a 550 code when it denies
29339 access, but for the predata ACL, note that the default success code is 354, not
29342 Notwithstanding the previous paragraph, for the QUIT ACL, unlike the others,
29343 the message modifier cannot override the 221 response code.
29345 The text in a &%message%& modifier is literal; any quotes are taken as
29346 literals, but because the string is expanded, backslash escapes are processed
29347 anyway. If the message contains newlines, this gives rise to a multi-line SMTP
29350 .vindex "&$acl_verify_message$&"
29351 For ACLs that are called by an &%acl =%& ACL condition, the message is
29352 stored in &$acl_verify_message$&, from which the calling ACL may use it.
29354 If &%message%& is used on a statement that verifies an address, the message
29355 specified overrides any message that is generated by the verification process.
29356 However, the original message is available in the variable
29357 &$acl_verify_message$&, so you can incorporate it into your message if you
29358 wish. In particular, if you want the text from &%:fail:%& items in &(redirect)&
29359 routers to be passed back as part of the SMTP response, you should either not
29360 use a &%message%& modifier, or make use of &$acl_verify_message$&.
29362 For compatibility with previous releases of Exim, a &%message%& modifier that
29363 is used with a &%warn%& verb behaves in a similar way to the &%add_header%&
29364 modifier, but this usage is now deprecated. However, &%message%& acts only when
29365 all the conditions are true, wherever it appears in an ACL command, whereas
29366 &%add_header%& acts as soon as it is encountered. If &%message%& is used with
29367 &%warn%& in an ACL that is not concerned with receiving a message, it has no
29371 .vitem &*queue*&&~=&~<&'text'&>
29372 .cindex "&%queue%& ACL modifier"
29373 .cindex "named queues" "selecting in ACL"
29374 This modifier specifies the use of a named queue for spool files
29376 It can only be used before the message is received (i.e. not in
29378 This could be used, for example, for known high-volume burst sources
29379 of traffic, or for quarantine of messages.
29380 Separate queue-runner processes will be needed for named queues.
29381 If the text after expansion is empty, the default queue is used.
29384 .vitem &*remove_header*&&~=&~<&'text'&>
29385 This modifier specifies one or more header names in a colon-separated list
29386 that are to be removed from an incoming message, assuming, of course, that
29387 the message is ultimately accepted. For details, see section &<<SECTremoveheadacl>>&.
29390 .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&>
29391 .cindex "&%set%& ACL modifier"
29392 This modifier puts a value into one of the ACL variables (see section
29393 &<<SECTaclvariables>>&).
29396 .vitem &*udpsend*&&~=&~<&'parameters'&>
29397 .cindex "UDP communications"
29398 This modifier sends a UDP packet, for purposes such as statistics
29399 collection or behaviour monitoring. The parameters are expanded, and
29400 the result of the expansion must be a colon-separated list consisting
29401 of a destination server, port number, and the packet contents. The
29402 server can be specified as a host name or IPv4 or IPv6 address. The
29403 separator can be changed with the usual angle bracket syntax. For
29404 example, you might want to collect information on which hosts connect
29407 udpsend = <; 2001:dB8::dead:beef ; 1234 ;\
29408 $tod_zulu $sender_host_address
29415 .section "Use of the control modifier" "SECTcontrols"
29416 .cindex "&%control%& ACL modifier"
29417 The &%control%& modifier supports the following settings:
29420 .vitem &*control&~=&~allow_auth_unadvertised*&
29421 This modifier allows a client host to use the SMTP AUTH command even when it
29422 has not been advertised in response to EHLO. Furthermore, because there are
29423 apparently some really broken clients that do this, Exim will accept AUTH after
29424 HELO (rather than EHLO) when this control is set. It should be used only if you
29425 really need it, and you should limit its use to those broken clients that do
29426 not work without it. For example:
29428 warn hosts = 192.168.34.25
29429 control = allow_auth_unadvertised
29431 Normally, when an Exim server receives an AUTH command, it checks the name of
29432 the authentication mechanism that is given in the command to ensure that it
29433 matches an advertised mechanism. When this control is set, the check that a
29434 mechanism has been advertised is bypassed. Any configured mechanism can be used
29435 by the client. This control is permitted only in the connection and HELO ACLs.
29438 .vitem &*control&~=&~caseful_local_part*& &&&
29439 &*control&~=&~caselower_local_part*&
29440 .cindex "&ACL;" "case of local part in"
29441 .cindex "case of local parts"
29442 .vindex "&$local_part$&"
29443 These two controls are permitted only in the ACL specified by &%acl_smtp_rcpt%&
29444 (that is, during RCPT processing). By default, the contents of &$local_part$&
29445 are lower cased before ACL processing. If &"caseful_local_part"& is specified,
29446 any uppercase letters in the original local part are restored in &$local_part$&
29447 for the rest of the ACL, or until a control that sets &"caselower_local_part"&
29450 These controls affect only the current recipient. Moreover, they apply only to
29451 local part handling that takes place directly in the ACL (for example, as a key
29452 in lookups). If a test to verify the recipient is obeyed, the case-related
29453 handling of the local part during the verification is controlled by the router
29454 configuration (see the &%caseful_local_part%& generic router option).
29456 This facility could be used, for example, to add a spam score to local parts
29457 containing upper case letters. For example, using &$acl_m4$& to accumulate the
29460 warn control = caseful_local_part
29461 set acl_m4 = ${eval:\
29463 ${if match{$local_part}{[A-Z]}{1}{0}}\
29465 control = caselower_local_part
29467 Notice that we put back the lower cased version afterwards, assuming that
29468 is what is wanted for subsequent tests.
29471 .vitem &*control&~=&~cutthrough_delivery/*&<&'options'&>
29472 .cindex "&ACL;" "cutthrough routing"
29473 .cindex "cutthrough" "requesting"
29474 This option requests delivery be attempted while the item is being received.
29476 The option is usable in the RCPT ACL.
29477 If enabled for a message received via smtp and routed to an smtp transport,
29478 and only one transport, interface, destination host and port combination
29479 is used for all recipients of the message,
29480 then the delivery connection is made while the receiving connection is open
29481 and data is copied from one to the other.
29483 An attempt to set this option for any recipient but the first
29484 for a mail will be quietly ignored.
29485 If a recipient-verify callout
29487 connection is subsequently
29488 requested in the same ACL it is held open and used for
29489 any subsequent recipients and the data,
29490 otherwise one is made after the initial RCPT ACL completes.
29492 Note that routers are used in verify mode,
29493 and cannot depend on content of received headers.
29494 Note also that headers cannot be
29495 modified by any of the post-data ACLs (DATA, MIME and DKIM).
29496 Headers may be modified by routers (subject to the above) and transports.
29497 The &'Received-By:'& header is generated as soon as the body reception starts,
29498 rather than the traditional time after the full message is received;
29499 this will affect the timestamp.
29501 All the usual ACLs are called; if one results in the message being
29502 rejected, all effort spent in delivery (including the costs on
29503 the ultimate destination) will be wasted.
29504 Note that in the case of data-time ACLs this includes the entire
29507 Cutthrough delivery is not supported via transport-filters or when DKIM signing
29508 of outgoing messages is done, because it sends data to the ultimate destination
29509 before the entire message has been received from the source.
29510 It is not supported for messages received with the SMTP PRDR
29514 Should the ultimate destination system positively accept or reject the mail,
29515 a corresponding indication is given to the source system and nothing is queued.
29516 If the item is successfully delivered in cutthrough mode
29517 the delivery log lines are tagged with ">>" rather than "=>" and appear
29518 before the acceptance "<=" line.
29520 If there is a temporary error the item is queued for later delivery in the
29522 This behaviour can be adjusted by appending the option &*defer=*&<&'value'&>
29523 to the control; the default value is &"spool"& and the alternate value
29524 &"pass"& copies an SMTP defer response from the target back to the initiator
29525 and does not queue the message.
29526 Note that this is independent of any recipient verify conditions in the ACL.
29528 Delivery in this mode avoids the generation of a bounce mail to a
29530 sender when the destination system is doing content-scan based rejection.
29533 .vitem &*control&~=&~debug/*&<&'options'&>
29534 .cindex "&ACL;" "enabling debug logging"
29535 .cindex "debugging" "enabling from an ACL"
29536 This control turns on debug logging, almost as though Exim had been invoked
29537 with &`-d`&, with the output going to a new logfile in the usual logs directory,
29538 by default called &'debuglog'&.
29539 The filename can be adjusted with the &'tag'& option, which
29540 may access any variables already defined. The logging may be adjusted with
29541 the &'opts'& option, which takes the same values as the &`-d`& command-line
29543 Logging started this way may be stopped, and the file removed,
29544 with the &'kill'& option.
29545 Some examples (which depend on variables that don't exist in all
29549 control = debug/tag=.$sender_host_address
29550 control = debug/opts=+expand+acl
29551 control = debug/tag=.$message_exim_id/opts=+expand
29552 control = debug/kill
29556 .vitem &*control&~=&~dkim_disable_verify*&
29557 .cindex "disable DKIM verify"
29558 .cindex "DKIM" "disable verify"
29559 This control turns off DKIM verification processing entirely. For details on
29560 the operation and configuration of DKIM, see section &<<SECDKIM>>&.
29563 .vitem &*control&~=&~dscp/*&<&'value'&>
29564 .cindex "&ACL;" "setting DSCP value"
29565 .cindex "DSCP" "inbound"
29566 This option causes the DSCP value associated with the socket for the inbound
29567 connection to be adjusted to a given value, given as one of a number of fixed
29568 strings or to numeric value.
29569 The &%-bI:dscp%& option may be used to ask Exim which names it knows of.
29570 Common values include &`throughput`&, &`mincost`&, and on newer systems
29571 &`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F.
29573 The outbound packets from Exim will be marked with this value in the header
29574 (for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee
29575 that these values will have any effect, not be stripped by networking
29576 equipment, or do much of anything without cooperation with your Network
29577 Engineer and those of all network operators between the source and destination.
29580 .vitem &*control&~=&~enforce_sync*& &&&
29581 &*control&~=&~no_enforce_sync*&
29582 .cindex "SMTP" "synchronization checking"
29583 .cindex "synchronization checking in SMTP"
29584 These controls make it possible to be selective about when SMTP synchronization
29585 is enforced. The global option &%smtp_enforce_sync%& specifies the initial
29586 state of the switch (it is true by default). See the description of this option
29587 in chapter &<<CHAPmainconfig>>& for details of SMTP synchronization checking.
29589 The effect of these two controls lasts for the remainder of the SMTP
29590 connection. They can appear in any ACL except the one for the non-SMTP
29591 messages. The most straightforward place to put them is in the ACL defined by
29592 &%acl_smtp_connect%&, which is run at the start of an incoming SMTP connection,
29593 before the first synchronization check. The expected use is to turn off the
29594 synchronization checks for badly-behaved hosts that you nevertheless need to
29598 .vitem &*control&~=&~fakedefer/*&<&'message'&>
29599 .cindex "fake defer"
29600 .cindex "defer, fake"
29601 This control works in exactly the same way as &%fakereject%& (described below)
29602 except that it causes an SMTP 450 response after the message data instead of a
29603 550 response. You must take care when using &%fakedefer%& because it causes the
29604 messages to be duplicated when the sender retries. Therefore, you should not
29605 use &%fakedefer%& if the message is to be delivered normally.
29607 .vitem &*control&~=&~fakereject/*&<&'message'&>
29608 .cindex "fake rejection"
29609 .cindex "rejection, fake"
29610 This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other
29611 words, only when an SMTP message is being received. If Exim accepts the
29612 message, instead the final 250 response, a 550 rejection message is sent.
29613 However, Exim proceeds to deliver the message as normal. The control applies
29614 only to the current message, not to any subsequent ones that may be received in
29615 the same SMTP connection.
29617 The text for the 550 response is taken from the &%control%& modifier. If no
29618 message is supplied, the following is used:
29620 550-Your message has been rejected but is being
29621 550-kept for evaluation.
29622 550-If it was a legitimate message, it may still be
29623 550 delivered to the target recipient(s).
29625 This facility should be used with extreme caution.
29627 .vitem &*control&~=&~freeze*&
29628 .cindex "frozen messages" "forcing in ACL"
29629 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
29630 other words, only when a message is being received. If the message is accepted,
29631 it is placed on Exim's queue and frozen. The control applies only to the
29632 current message, not to any subsequent ones that may be received in the same
29635 This modifier can optionally be followed by &`/no_tell`&. If the global option
29636 &%freeze_tell%& is set, it is ignored for the current message (that is, nobody
29637 is told about the freezing), provided all the &*control=freeze*& modifiers that
29638 are obeyed for the current message have the &`/no_tell`& option.
29640 .vitem &*control&~=&~no_delay_flush*&
29641 .cindex "SMTP" "output flushing, disabling for delay"
29642 Exim normally flushes SMTP output before implementing a delay in an ACL, to
29643 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
29644 use. This control, as long as it is encountered before the &%delay%& modifier,
29645 disables such output flushing.
29647 .vitem &*control&~=&~no_callout_flush*&
29648 .cindex "SMTP" "output flushing, disabling for callout"
29649 Exim normally flushes SMTP output before performing a callout in an ACL, to
29650 avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in
29651 use. This control, as long as it is encountered before the &%verify%& condition
29652 that causes the callout, disables such output flushing.
29654 .vitem &*control&~=&~no_mbox_unspool*&
29655 This control is available when Exim is compiled with the content scanning
29656 extension. Content scanning may require a copy of the current message, or parts
29657 of it, to be written in &"mbox format"& to a spool file, for passing to a virus
29658 or spam scanner. Normally, such copies are deleted when they are no longer
29659 needed. If this control is set, the copies are not deleted. The control applies
29660 only to the current message, not to any subsequent ones that may be received in
29661 the same SMTP connection. It is provided for debugging purposes and is unlikely
29662 to be useful in production.
29664 .vitem &*control&~=&~no_multiline_responses*&
29665 .cindex "multiline responses, suppressing"
29666 This control is permitted for any ACL except the one for non-SMTP messages.
29667 It seems that there are broken clients in use that cannot handle multiline
29668 SMTP responses, despite the fact that RFC 821 defined them over 20 years ago.
29670 If this control is set, multiline SMTP responses from ACL rejections are
29671 suppressed. One way of doing this would have been to put out these responses as
29672 one long line. However, RFC 2821 specifies a maximum of 512 bytes per response
29673 (&"use multiline responses for more"& it says &-- ha!), and some of the
29674 responses might get close to that. So this facility, which is after all only a
29675 sop to broken clients, is implemented by doing two very easy things:
29678 Extra information that is normally output as part of a rejection caused by
29679 sender verification failure is omitted. Only the final line (typically &"sender
29680 verification failed"&) is sent.
29682 If a &%message%& modifier supplies a multiline response, only the first
29686 The setting of the switch can, of course, be made conditional on the
29687 calling host. Its effect lasts until the end of the SMTP connection.
29689 .vitem &*control&~=&~no_pipelining*&
29690 .cindex "PIPELINING" "suppressing advertising"
29691 This control turns off the advertising of the PIPELINING extension to SMTP in
29692 the current session. To be useful, it must be obeyed before Exim sends its
29693 response to an EHLO command. Therefore, it should normally appear in an ACL
29694 controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
29695 &%pipelining_advertise_hosts%&.
29697 .vitem &*control&~=&~queue_only*&
29698 .oindex "&%queue_only%&"
29699 .cindex "queueing incoming messages"
29700 This control is permitted only for the MAIL, RCPT, DATA, and non-SMTP ACLs, in
29701 other words, only when a message is being received. If the message is accepted,
29702 it is placed on Exim's queue and left there for delivery by a subsequent queue
29703 runner. No immediate delivery process is started. In other words, it has the
29704 effect as the &%queue_only%& global option. However, the control applies only
29705 to the current message, not to any subsequent ones that may be received in the
29706 same SMTP connection.
29708 .vitem &*control&~=&~submission/*&<&'options'&>
29709 .cindex "message" "submission"
29710 .cindex "submission mode"
29711 This control is permitted only for the MAIL, RCPT, and start of data ACLs (the
29712 latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that
29713 the current message is a submission from a local MUA. In this case, Exim
29714 operates in &"submission mode"&, and applies certain fixups to the message if
29715 necessary. For example, it adds a &'Date:'& header line if one is not present.
29716 This control is not permitted in the &%acl_smtp_data%& ACL, because that is too
29717 late (the message has already been created).
29719 Chapter &<<CHAPmsgproc>>& describes the processing that Exim applies to
29720 messages. Section &<<SECTsubmodnon>>& covers the processing that happens in
29721 submission mode; the available options for this control are described there.
29722 The control applies only to the current message, not to any subsequent ones
29723 that may be received in the same SMTP connection.
29725 .vitem &*control&~=&~suppress_local_fixups*&
29726 .cindex "submission fixups, suppressing"
29727 This control applies to locally submitted (non TCP/IP) messages, and is the
29728 complement of &`control = submission`&. It disables the fixups that are
29729 normally applied to locally-submitted messages. Specifically:
29732 Any &'Sender:'& header line is left alone (in this respect, it is a
29733 dynamic version of &%local_sender_retain%&).
29735 No &'Message-ID:'&, &'From:'&, or &'Date:'& header lines are added.
29737 There is no check that &'From:'& corresponds to the actual sender.
29740 This control may be useful when a remotely-originated message is accepted,
29741 passed to some scanning program, and then re-submitted for delivery. It can be
29742 used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
29743 and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's
29746 &*Note:*& This control applies only to the current message, not to any others
29747 that are being submitted at the same time using &%-bs%& or &%-bS%&.
29749 .vitem &*control&~=&~utf8_downconvert*&
29750 This control enables conversion of UTF-8 in message addresses
29752 For details see section &<<SECTi18nMTA>>&.
29756 .section "Summary of message fixup control" "SECTsummesfix"
29757 All four possibilities for message fixups can be specified:
29760 Locally submitted, fixups applied: the default.
29762 Locally submitted, no fixups applied: use
29763 &`control = suppress_local_fixups`&.
29765 Remotely submitted, no fixups applied: the default.
29767 Remotely submitted, fixups applied: use &`control = submission`&.
29772 .section "Adding header lines in ACLs" "SECTaddheadacl"
29773 .cindex "header lines" "adding in an ACL"
29774 .cindex "header lines" "position of added lines"
29775 .cindex "&%add_header%& ACL modifier"
29776 The &%add_header%& modifier can be used to add one or more extra header lines
29777 to an incoming message, as in this example:
29779 warn dnslists = sbl.spamhaus.org : \
29780 dialup.mail-abuse.org
29781 add_header = X-blacklisted-at: $dnslist_domain
29783 The &%add_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
29784 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
29785 receiving a message). The message must ultimately be accepted for
29786 &%add_header%& to have any significant effect. You can use &%add_header%& with
29787 any ACL verb, including &%deny%& (though this is potentially useful only in a
29790 Headers will not be added to the message if the modifier is used in
29791 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
29793 Leading and trailing newlines are removed from
29794 the data for the &%add_header%& modifier; if it then
29795 contains one or more newlines that
29796 are not followed by a space or a tab, it is assumed to contain multiple header
29797 lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the
29798 front of any line that is not a valid header line.
29800 Added header lines are accumulated during the MAIL, RCPT, and predata ACLs.
29801 They are added to the message before processing the DATA and MIME ACLs.
29802 However, if an identical header line is requested more than once, only one copy
29803 is actually added to the message. Further header lines may be accumulated
29804 during the DATA and MIME ACLs, after which they are added to the message, again
29805 with duplicates suppressed. Thus, it is possible to add two identical header
29806 lines to an SMTP message, but only if one is added before DATA and one after.
29807 In the case of non-SMTP messages, new headers are accumulated during the
29808 non-SMTP ACLs, and are added to the message after all the ACLs have run. If a
29809 message is rejected after DATA or by the non-SMTP ACL, all added header lines
29810 are included in the entry that is written to the reject log.
29812 .cindex "header lines" "added; visibility of"
29813 Header lines are not visible in string expansions
29815 until they are added to the
29816 message. It follows that header lines defined in the MAIL, RCPT, and predata
29817 ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly,
29818 header lines that are added by the DATA or MIME ACLs are not visible in those
29819 ACLs. Because of this restriction, you cannot use header lines as a way of
29820 passing data between (for example) the MAIL and RCPT ACLs. If you want to do
29821 this, you can use ACL variables, as described in section
29822 &<<SECTaclvariables>>&.
29824 The list of headers yet to be added is given by the &%$headers_added%& variable.
29826 The &%add_header%& modifier acts immediately as it is encountered during the
29827 processing of an ACL. Notice the difference between these two cases:
29829 &`accept add_header = ADDED: some text`&
29830 &` `&<&'some condition'&>
29832 &`accept `&<&'some condition'&>
29833 &` add_header = ADDED: some text`&
29835 In the first case, the header line is always added, whether or not the
29836 condition is true. In the second case, the header line is added only if the
29837 condition is true. Multiple occurrences of &%add_header%& may occur in the same
29838 ACL statement. All those that are encountered before a condition fails are
29841 .cindex "&%warn%& ACL verb"
29842 For compatibility with previous versions of Exim, a &%message%& modifier for a
29843 &%warn%& verb acts in the same way as &%add_header%&, except that it takes
29844 effect only if all the conditions are true, even if it appears before some of
29845 them. Furthermore, only the last occurrence of &%message%& is honoured. This
29846 usage of &%message%& is now deprecated. If both &%add_header%& and &%message%&
29847 are present on a &%warn%& verb, both are processed according to their
29850 By default, new header lines are added to a message at the end of the existing
29851 header lines. However, you can specify that any particular header line should
29852 be added right at the start (before all the &'Received:'& lines), immediately
29853 after the first block of &'Received:'& lines, or immediately before any line
29854 that is not a &'Received:'& or &'Resent-something:'& header.
29856 This is done by specifying &":at_start:"&, &":after_received:"&, or
29857 &":at_start_rfc:"& (or, for completeness, &":at_end:"&) before the text of the
29858 header line, respectively. (Header text cannot start with a colon, as there has
29859 to be a header name first.) For example:
29861 warn add_header = \
29862 :after_received:X-My-Header: something or other...
29864 If more than one header line is supplied in a single &%add_header%& modifier,
29865 each one is treated independently and can therefore be placed differently. If
29866 you add more than one line at the start, or after the Received: block, they end
29867 up in reverse order.
29869 &*Warning*&: This facility currently applies only to header lines that are
29870 added in an ACL. It does NOT work for header lines that are added in a
29871 system filter or in a router or transport.
29875 .section "Removing header lines in ACLs" "SECTremoveheadacl"
29876 .cindex "header lines" "removing in an ACL"
29877 .cindex "header lines" "position of removed lines"
29878 .cindex "&%remove_header%& ACL modifier"
29879 The &%remove_header%& modifier can be used to remove one or more header lines
29880 from an incoming message, as in this example:
29882 warn message = Remove internal headers
29883 remove_header = x-route-mail1 : x-route-mail2
29885 The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA,
29886 MIME, DKIM, and non-SMTP ACLs (in other words, those that are concerned with
29887 receiving a message). The message must ultimately be accepted for
29888 &%remove_header%& to have any significant effect. You can use &%remove_header%&
29889 with any ACL verb, including &%deny%&, though this is really not useful for
29890 any verb that doesn't result in a delivered message.
29892 Headers will not be removed from the message if the modifier is used in
29893 DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing.
29895 More than one header can be removed at the same time by using a colon separated
29896 list of header names. The header matching is case insensitive. Wildcards are
29897 not permitted, nor is list expansion performed, so you cannot use hostlists to
29898 create a list of headers, however both connection and message variable expansion
29899 are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example:
29901 warn hosts = +internal_hosts
29902 set acl_c_ihdrs = x-route-mail1 : x-route-mail2
29903 warn message = Remove internal headers
29904 remove_header = $acl_c_ihdrs
29906 Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs.
29907 Matching header lines are removed from the message before processing the DATA and MIME ACLs.
29908 If multiple header lines match, all are removed.
29909 There is no harm in attempting to remove the same header twice nor in removing
29910 a non-existent header. Further header lines to be removed may be accumulated
29911 during the DATA and MIME ACLs, after which they are removed from the message,
29912 if present. In the case of non-SMTP messages, headers to be removed are
29913 accumulated during the non-SMTP ACLs, and are removed from the message after
29914 all the ACLs have run. If a message is rejected after DATA or by the non-SMTP
29915 ACL, there really is no effect because there is no logging of what headers
29916 would have been removed.
29918 .cindex "header lines" "removed; visibility of"
29919 Header lines are not visible in string expansions until the DATA phase when it
29920 is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are
29921 not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are
29922 removed by the DATA or MIME ACLs are still visible in those ACLs. Because of
29923 this restriction, you cannot use header lines as a way of controlling data
29924 passed between (for example) the MAIL and RCPT ACLs. If you want to do this,
29925 you should instead use ACL variables, as described in section
29926 &<<SECTaclvariables>>&.
29928 The &%remove_header%& modifier acts immediately as it is encountered during the
29929 processing of an ACL. Notice the difference between these two cases:
29931 &`accept remove_header = X-Internal`&
29932 &` `&<&'some condition'&>
29934 &`accept `&<&'some condition'&>
29935 &` remove_header = X-Internal`&
29937 In the first case, the header line is always removed, whether or not the
29938 condition is true. In the second case, the header line is removed only if the
29939 condition is true. Multiple occurrences of &%remove_header%& may occur in the
29940 same ACL statement. All those that are encountered before a condition fails
29943 &*Warning*&: This facility currently applies only to header lines that are
29944 present during ACL processing. It does NOT remove header lines that are added
29945 in a system filter or in a router or transport.
29950 .section "ACL conditions" "SECTaclconditions"
29951 .cindex "&ACL;" "conditions; list of"
29952 Some of the conditions listed in this section are available only when Exim is
29953 compiled with the content-scanning extension. They are included here briefly
29954 for completeness. More detailed descriptions can be found in the discussion on
29955 content scanning in chapter &<<CHAPexiscan>>&.
29957 Not all conditions are relevant in all circumstances. For example, testing
29958 senders and recipients does not make sense in an ACL that is being run as the
29959 result of the arrival of an ETRN command, and checks on message headers can be
29960 done only in the ACLs specified by &%acl_smtp_data%& and &%acl_not_smtp%&. You
29961 can use the same condition (with different parameters) more than once in the
29962 same ACL statement. This provides a way of specifying an &"and"& conjunction.
29963 The conditions are as follows:
29967 .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&>
29968 .cindex "&ACL;" "nested"
29969 .cindex "&ACL;" "indirect"
29970 .cindex "&ACL;" "arguments"
29971 .cindex "&%acl%& ACL condition"
29972 The possible values of the argument are the same as for the
29973 &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns
29974 &"accept"& the condition is true; if it returns &"deny"& the condition is
29975 false. If it returns &"defer"&, the current ACL returns &"defer"& unless the
29976 condition is on a &%warn%& verb. In that case, a &"defer"& return makes the
29977 condition false. This means that further processing of the &%warn%& verb
29978 ceases, but processing of the ACL continues.
29980 If the argument is a named ACL, up to nine space-separated optional values
29981 can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9,
29982 and $acl_narg is set to the count of values.
29983 Previous values of these variables are restored after the call returns.
29984 The name and values are expanded separately.
29985 Note that spaces in complex expansions which are used as arguments
29986 will act as argument separators.
29988 If the nested &%acl%& returns &"drop"& and the outer condition denies access,
29989 the connection is dropped. If it returns &"discard"&, the verb must be
29990 &%accept%& or &%discard%&, and the action is taken immediately &-- no further
29991 conditions are tested.
29993 ACLs may be nested up to 20 deep; the limit exists purely to catch runaway
29994 loops. This condition allows you to use different ACLs in different
29995 circumstances. For example, different ACLs can be used to handle RCPT commands
29996 for different local users or different local domains.
29998 .vitem &*authenticated&~=&~*&<&'string&~list'&>
29999 .cindex "&%authenticated%& ACL condition"
30000 .cindex "authentication" "ACL checking"
30001 .cindex "&ACL;" "testing for authentication"
30002 If the SMTP connection is not authenticated, the condition is false. Otherwise,
30003 the name of the authenticator is tested against the list. To test for
30004 authentication by any authenticator, you can set
30009 .vitem &*condition&~=&~*&<&'string'&>
30010 .cindex "&%condition%& ACL condition"
30011 .cindex "customizing" "ACL condition"
30012 .cindex "&ACL;" "customized test"
30013 .cindex "&ACL;" "testing, customized"
30014 This feature allows you to make up custom conditions. If the result of
30015 expanding the string is an empty string, the number zero, or one of the strings
30016 &"no"& or &"false"&, the condition is false. If the result is any non-zero
30017 number, or one of the strings &"yes"& or &"true"&, the condition is true. For
30018 any other value, some error is assumed to have occurred, and the ACL returns
30019 &"defer"&. However, if the expansion is forced to fail, the condition is
30020 ignored. The effect is to treat it as true, whether it is positive or
30023 .vitem &*decode&~=&~*&<&'location'&>
30024 .cindex "&%decode%& ACL condition"
30025 This condition is available only when Exim is compiled with the
30026 content-scanning extension, and it is allowed only in the ACL defined by
30027 &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file.
30028 If all goes well, the condition is true. It is false only if there are
30029 problems such as a syntax error or a memory shortage. For more details, see
30030 chapter &<<CHAPexiscan>>&.
30032 .vitem &*dnslists&~=&~*&<&'list&~of&~domain&~names&~and&~other&~data'&>
30033 .cindex "&%dnslists%& ACL condition"
30034 .cindex "DNS list" "in ACL"
30035 .cindex "black list (DNS)"
30036 .cindex "&ACL;" "testing a DNS list"
30037 This condition checks for entries in DNS black lists. These are also known as
30038 &"RBL lists"&, after the original Realtime Blackhole List, but note that the
30039 use of the lists at &'mail-abuse.org'& now carries a charge. There are too many
30040 different variants of this condition to describe briefly here. See sections
30041 &<<SECTmorednslists>>&&--&<<SECTmorednslistslast>>& for details.
30043 .vitem &*domains&~=&~*&<&'domain&~list'&>
30044 .cindex "&%domains%& ACL condition"
30045 .cindex "domain" "ACL checking"
30046 .cindex "&ACL;" "testing a recipient domain"
30047 .vindex "&$domain_data$&"
30048 This condition is relevant only after a RCPT command. It checks that the domain
30049 of the recipient address is in the domain list. If percent-hack processing is
30050 enabled, it is done before this test is done. If the check succeeds with a
30051 lookup, the result of the lookup is placed in &$domain_data$& until the next
30054 &*Note carefully*& (because many people seem to fall foul of this): you cannot
30055 use &%domains%& in a DATA ACL.
30058 .vitem &*encrypted&~=&~*&<&'string&~list'&>
30059 .cindex "&%encrypted%& ACL condition"
30060 .cindex "encryption" "checking in an ACL"
30061 .cindex "&ACL;" "testing for encryption"
30062 If the SMTP connection is not encrypted, the condition is false. Otherwise, the
30063 name of the cipher suite in use is tested against the list. To test for
30064 encryption without testing for any specific cipher suite(s), set
30070 .vitem &*hosts&~=&~*&<&'host&~list'&>
30071 .cindex "&%hosts%& ACL condition"
30072 .cindex "host" "ACL checking"
30073 .cindex "&ACL;" "testing the client host"
30074 This condition tests that the calling host matches the host list. If you have
30075 name lookups or wildcarded host names and IP addresses in the same host list,
30076 you should normally put the IP addresses first. For example, you could have:
30078 accept hosts = 10.9.8.7 : dbm;/etc/friendly/hosts
30080 The lookup in this example uses the host name for its key. This is implied by
30081 the lookup type &"dbm"&. (For a host address lookup you would use &"net-dbm"&
30082 and it wouldn't matter which way round you had these two items.)
30084 The reason for the problem with host names lies in the left-to-right way that
30085 Exim processes lists. It can test IP addresses without doing any DNS lookups,
30086 but when it reaches an item that requires a host name, it fails if it cannot
30087 find a host name to compare with the pattern. If the above list is given in the
30088 opposite order, the &%accept%& statement fails for a host whose name cannot be
30089 found, even if its IP address is 10.9.8.7.
30091 If you really do want to do the name check first, and still recognize the IP
30092 address even if the name lookup fails, you can rewrite the ACL like this:
30094 accept hosts = dbm;/etc/friendly/hosts
30095 accept hosts = 10.9.8.7
30097 The default action on failing to find the host name is to assume that the host
30098 is not in the list, so the first &%accept%& statement fails. The second
30099 statement can then check the IP address.
30101 .vindex "&$host_data$&"
30102 If a &%hosts%& condition is satisfied by means of a lookup, the result
30103 of the lookup is made available in the &$host_data$& variable. This
30104 allows you, for example, to set up a statement like this:
30106 deny hosts = net-lsearch;/some/file
30107 message = $host_data
30109 which gives a custom error message for each denied host.
30111 .vitem &*local_parts&~=&~*&<&'local&~part&~list'&>
30112 .cindex "&%local_parts%& ACL condition"
30113 .cindex "local part" "ACL checking"
30114 .cindex "&ACL;" "testing a local part"
30115 .vindex "&$local_part_data$&"
30116 This condition is relevant only after a RCPT command. It checks that the local
30117 part of the recipient address is in the list. If percent-hack processing is
30118 enabled, it is done before this test. If the check succeeds with a lookup, the
30119 result of the lookup is placed in &$local_part_data$&, which remains set until
30120 the next &%local_parts%& test.
30122 .vitem &*malware&~=&~*&<&'option'&>
30123 .cindex "&%malware%& ACL condition"
30124 .cindex "&ACL;" "virus scanning"
30125 .cindex "&ACL;" "scanning for viruses"
30126 This condition is available only when Exim is compiled with the
30127 content-scanning extension. It causes the incoming message to be scanned for
30128 viruses. For details, see chapter &<<CHAPexiscan>>&.
30130 .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&>
30131 .cindex "&%mime_regex%& ACL condition"
30132 .cindex "&ACL;" "testing by regex matching"
30133 This condition is available only when Exim is compiled with the
30134 content-scanning extension, and it is allowed only in the ACL defined by
30135 &%acl_smtp_mime%&. It causes the current MIME part to be scanned for a match
30136 with any of the regular expressions. For details, see chapter
30139 .vitem &*ratelimit&~=&~*&<&'parameters'&>
30140 .cindex "rate limiting"
30141 This condition can be used to limit the rate at which a user or host submits
30142 messages. Details are given in section &<<SECTratelimiting>>&.
30144 .vitem &*recipients&~=&~*&<&'address&~list'&>
30145 .cindex "&%recipients%& ACL condition"
30146 .cindex "recipient" "ACL checking"
30147 .cindex "&ACL;" "testing a recipient"
30148 This condition is relevant only after a RCPT command. It checks the entire
30149 recipient address against a list of recipients.
30151 .vitem &*regex&~=&~*&<&'list&~of&~regular&~expressions'&>
30152 .cindex "&%regex%& ACL condition"
30153 .cindex "&ACL;" "testing by regex matching"
30154 This condition is available only when Exim is compiled with the
30155 content-scanning extension, and is available only in the DATA, MIME, and
30156 non-SMTP ACLs. It causes the incoming message to be scanned for a match with
30157 any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
30159 .vitem &*sender_domains&~=&~*&<&'domain&~list'&>
30160 .cindex "&%sender_domains%& ACL condition"
30161 .cindex "sender" "ACL checking"
30162 .cindex "&ACL;" "testing a sender domain"
30163 .vindex "&$domain$&"
30164 .vindex "&$sender_address_domain$&"
30165 This condition tests the domain of the sender of the message against the given
30166 domain list. &*Note*&: The domain of the sender address is in
30167 &$sender_address_domain$&. It is &'not'& put in &$domain$& during the testing
30168 of this condition. This is an exception to the general rule for testing domain
30169 lists. It is done this way so that, if this condition is used in an ACL for a
30170 RCPT command, the recipient's domain (which is in &$domain$&) can be used to
30171 influence the sender checking.
30173 &*Warning*&: It is a bad idea to use this condition on its own as a control on
30174 relaying, because sender addresses are easily, and commonly, forged.
30176 .vitem &*senders&~=&~*&<&'address&~list'&>
30177 .cindex "&%senders%& ACL condition"
30178 .cindex "sender" "ACL checking"
30179 .cindex "&ACL;" "testing a sender"
30180 This condition tests the sender of the message against the given list. To test
30181 for a bounce message, which has an empty sender, set
30185 &*Warning*&: It is a bad idea to use this condition on its own as a control on
30186 relaying, because sender addresses are easily, and commonly, forged.
30188 .vitem &*spam&~=&~*&<&'username'&>
30189 .cindex "&%spam%& ACL condition"
30190 .cindex "&ACL;" "scanning for spam"
30191 This condition is available only when Exim is compiled with the
30192 content-scanning extension. It causes the incoming message to be scanned by
30193 SpamAssassin. For details, see chapter &<<CHAPexiscan>>&.
30195 .vitem &*verify&~=&~certificate*&
30196 .cindex "&%verify%& ACL condition"
30197 .cindex "TLS" "client certificate verification"
30198 .cindex "certificate" "verification of client"
30199 .cindex "&ACL;" "certificate verification"
30200 .cindex "&ACL;" "testing a TLS certificate"
30201 This condition is true in an SMTP session if the session is encrypted, and a
30202 certificate was received from the client, and the certificate was verified. The
30203 server requests a certificate only if the client matches &%tls_verify_hosts%&
30204 or &%tls_try_verify_hosts%& (see chapter &<<CHAPTLS>>&).
30206 .vitem &*verify&~=&~csa*&
30207 .cindex "CSA verification"
30208 This condition checks whether the sending host (the client) is authorized to
30209 send email. Details of how this works are given in section
30210 &<<SECTverifyCSA>>&.
30212 .vitem &*verify&~=&~header_names_ascii*&
30213 .cindex "&%verify%& ACL condition"
30214 .cindex "&ACL;" "verifying header names only ASCII"
30215 .cindex "header lines" "verifying header names only ASCII"
30216 .cindex "verifying" "header names only ASCII"
30217 This condition is relevant only in an ACL that is run after a message has been
30218 received, that is, in an ACL specified by &%acl_smtp_data%& or
30219 &%acl_not_smtp%&. It checks all header names (not the content) to make sure
30220 there are no non-ASCII characters, also excluding control characters. The
30221 allowable characters are decimal ASCII values 33 through 126.
30223 Exim itself will handle headers with non-ASCII characters, but it can cause
30224 problems for downstream applications, so this option will allow their
30225 detection and rejection in the DATA ACL's.
30227 .vitem &*verify&~=&~header_sender/*&<&'options'&>
30228 .cindex "&%verify%& ACL condition"
30229 .cindex "&ACL;" "verifying sender in the header"
30230 .cindex "header lines" "verifying the sender in"
30231 .cindex "sender" "verifying in header"
30232 .cindex "verifying" "sender in header"
30233 This condition is relevant only in an ACL that is run after a message has been
30234 received, that is, in an ACL specified by &%acl_smtp_data%& or
30235 &%acl_not_smtp%&. It checks that there is a verifiable address in at least one
30236 of the &'Sender:'&, &'Reply-To:'&, or &'From:'& header lines. Such an address
30237 is loosely thought of as a &"sender"& address (hence the name of the test).
30238 However, an address that appears in one of these headers need not be an address
30239 that accepts bounce messages; only sender addresses in envelopes are required
30240 to accept bounces. Therefore, if you use the callout option on this check, you
30241 might want to arrange for a non-empty address in the MAIL command.
30243 Details of address verification and the options are given later, starting at
30244 section &<<SECTaddressverification>>& (callouts are described in section
30245 &<<SECTcallver>>&). You can combine this condition with the &%senders%&
30246 condition to restrict it to bounce messages only:
30249 message = A valid sender header is required for bounces
30250 !verify = header_sender
30253 .vitem &*verify&~=&~header_syntax*&
30254 .cindex "&%verify%& ACL condition"
30255 .cindex "&ACL;" "verifying header syntax"
30256 .cindex "header lines" "verifying syntax"
30257 .cindex "verifying" "header syntax"
30258 This condition is relevant only in an ACL that is run after a message has been
30259 received, that is, in an ACL specified by &%acl_smtp_data%& or
30260 &%acl_not_smtp%&. It checks the syntax of all header lines that can contain
30261 lists of addresses (&'Sender:'&, &'From:'&, &'Reply-To:'&, &'To:'&, &'Cc:'&,
30262 and &'Bcc:'&), returning true if there are no problems.
30263 Unqualified addresses (local parts without domains) are
30264 permitted only in locally generated messages and from hosts that match
30265 &%sender_unqualified_hosts%& or &%recipient_unqualified_hosts%&, as
30268 Note that this condition is a syntax check only. However, a common spamming
30269 ploy used to be to send syntactically invalid headers such as
30273 and this condition can be used to reject such messages, though they are not as
30274 common as they used to be.
30276 .vitem &*verify&~=&~helo*&
30277 .cindex "&%verify%& ACL condition"
30278 .cindex "&ACL;" "verifying HELO/EHLO"
30279 .cindex "HELO" "verifying"
30280 .cindex "EHLO" "verifying"
30281 .cindex "verifying" "EHLO"
30282 .cindex "verifying" "HELO"
30283 This condition is true if a HELO or EHLO command has been received from the
30284 client host, and its contents have been verified. If there has been no previous
30285 attempt to verify the HELO/EHLO contents, it is carried out when this
30286 condition is encountered. See the description of the &%helo_verify_hosts%& and
30287 &%helo_try_verify_hosts%& options for details of how to request verification
30288 independently of this condition.
30290 For SMTP input that does not come over TCP/IP (the &%-bs%& command line
30291 option), this condition is always true.
30294 .vitem &*verify&~=&~not_blind*&
30295 .cindex "verifying" "not blind"
30296 .cindex "bcc recipients, verifying none"
30297 This condition checks that there are no blind (bcc) recipients in the message.
30298 Every envelope recipient must appear either in a &'To:'& header line or in a
30299 &'Cc:'& header line for this condition to be true. Local parts are checked
30300 case-sensitively; domains are checked case-insensitively. If &'Resent-To:'& or
30301 &'Resent-Cc:'& header lines exist, they are also checked. This condition can be
30302 used only in a DATA or non-SMTP ACL.
30304 There are, of course, many legitimate messages that make use of blind (bcc)
30305 recipients. This check should not be used on its own for blocking messages.
30308 .vitem &*verify&~=&~recipient/*&<&'options'&>
30309 .cindex "&%verify%& ACL condition"
30310 .cindex "&ACL;" "verifying recipient"
30311 .cindex "recipient" "verifying"
30312 .cindex "verifying" "recipient"
30313 .vindex "&$address_data$&"
30314 This condition is relevant only after a RCPT command. It verifies the current
30315 recipient. Details of address verification are given later, starting at section
30316 &<<SECTaddressverification>>&. After a recipient has been verified, the value
30317 of &$address_data$& is the last value that was set while routing the address.
30318 This applies even if the verification fails. When an address that is being
30319 verified is redirected to a single address, verification continues with the new
30320 address, and in that case, the subsequent value of &$address_data$& is the
30321 value for the child address.
30323 .vitem &*verify&~=&~reverse_host_lookup/*&<&'options'&>
30324 .cindex "&%verify%& ACL condition"
30325 .cindex "&ACL;" "verifying host reverse lookup"
30326 .cindex "host" "verifying reverse lookup"
30327 This condition ensures that a verified host name has been looked up from the IP
30328 address of the client host. (This may have happened already if the host name
30329 was needed for checking a host list, or if the host matched &%host_lookup%&.)
30330 Verification ensures that the host name obtained from a reverse DNS lookup, or
30331 one of its aliases, does, when it is itself looked up in the DNS, yield the
30332 original IP address.
30334 There is one possible option, &`defer_ok`&. If this is present and a
30335 DNS operation returns a temporary error, the verify condition succeeds.
30337 If this condition is used for a locally generated message (that is, when there
30338 is no client host involved), it always succeeds.
30340 .vitem &*verify&~=&~sender/*&<&'options'&>
30341 .cindex "&%verify%& ACL condition"
30342 .cindex "&ACL;" "verifying sender"
30343 .cindex "sender" "verifying"
30344 .cindex "verifying" "sender"
30345 This condition is relevant only after a MAIL or RCPT command, or after a
30346 message has been received (the &%acl_smtp_data%& or &%acl_not_smtp%& ACLs). If
30347 the message's sender is empty (that is, this is a bounce message), the
30348 condition is true. Otherwise, the sender address is verified.
30350 .vindex "&$address_data$&"
30351 .vindex "&$sender_address_data$&"
30352 If there is data in the &$address_data$& variable at the end of routing, its
30353 value is placed in &$sender_address_data$& at the end of verification. This
30354 value can be used in subsequent conditions and modifiers in the same ACL
30355 statement. It does not persist after the end of the current statement. If you
30356 want to preserve the value for longer, you can save it in an ACL variable.
30358 Details of verification are given later, starting at section
30359 &<<SECTaddressverification>>&. Exim caches the result of sender verification,
30360 to avoid doing it more than once per message.
30362 .vitem &*verify&~=&~sender=*&<&'address'&>&*/*&<&'options'&>
30363 .cindex "&%verify%& ACL condition"
30364 This is a variation of the previous option, in which a modified address is
30365 verified as a sender.
30367 Note that '/' is legal in local-parts; if the address may have such
30368 (eg. is generated from the received message)
30369 they must be protected from the options parsing by doubling:
30371 verify = sender=${sg{${address:$h_sender:}}{/}{//}}
30377 .section "Using DNS lists" "SECTmorednslists"
30378 .cindex "DNS list" "in ACL"
30379 .cindex "black list (DNS)"
30380 .cindex "&ACL;" "testing a DNS list"
30381 In its simplest form, the &%dnslists%& condition tests whether the calling host
30382 is on at least one of a number of DNS lists by looking up the inverted IP
30383 address in one or more DNS domains. (Note that DNS list domains are not mail
30384 domains, so the &`+`& syntax for named lists doesn't work - it is used for
30385 special options instead.) For example, if the calling host's IP
30386 address is 192.168.62.43, and the ACL statement is
30388 deny dnslists = blackholes.mail-abuse.org : \
30389 dialups.mail-abuse.org
30391 the following records are looked up:
30393 43.62.168.192.blackholes.mail-abuse.org
30394 43.62.168.192.dialups.mail-abuse.org
30396 As soon as Exim finds an existing DNS record, processing of the list stops.
30397 Thus, multiple entries on the list provide an &"or"& conjunction. If you want
30398 to test that a host is on more than one list (an &"and"& conjunction), you can
30399 use two separate conditions:
30401 deny dnslists = blackholes.mail-abuse.org
30402 dnslists = dialups.mail-abuse.org
30404 If a DNS lookup times out or otherwise fails to give a decisive answer, Exim
30405 behaves as if the host does not match the list item, that is, as if the DNS
30406 record does not exist. If there are further items in the DNS list, they are
30409 This is usually the required action when &%dnslists%& is used with &%deny%&
30410 (which is the most common usage), because it prevents a DNS failure from
30411 blocking mail. However, you can change this behaviour by putting one of the
30412 following special items in the list:
30414 &`+include_unknown `& behave as if the item is on the list
30415 &`+exclude_unknown `& behave as if the item is not on the list (default)
30416 &`+defer_unknown `& give a temporary error
30418 .cindex "&`+include_unknown`&"
30419 .cindex "&`+exclude_unknown`&"
30420 .cindex "&`+defer_unknown`&"
30421 Each of these applies to any subsequent items on the list. For example:
30423 deny dnslists = +defer_unknown : foo.bar.example
30425 Testing the list of domains stops as soon as a match is found. If you want to
30426 warn for one list and block for another, you can use two different statements:
30428 deny dnslists = blackholes.mail-abuse.org
30429 warn message = X-Warn: sending host is on dialups list
30430 dnslists = dialups.mail-abuse.org
30432 .cindex caching "of dns lookup"
30434 DNS list lookups are cached by Exim for the duration of the SMTP session
30435 (but limited by the DNS return TTL value),
30436 so a lookup based on the IP address is done at most once for any incoming
30437 connection (assuming long-enough TTL).
30438 Exim does not share information between multiple incoming
30439 connections (but your local name server cache should be active).
30443 .section "Specifying the IP address for a DNS list lookup" "SECID201"
30444 .cindex "DNS list" "keyed by explicit IP address"
30445 By default, the IP address that is used in a DNS list lookup is the IP address
30446 of the calling host. However, you can specify another IP address by listing it
30447 after the domain name, introduced by a slash. For example:
30449 deny dnslists = black.list.tld/192.168.1.2
30451 This feature is not very helpful with explicit IP addresses; it is intended for
30452 use with IP addresses that are looked up, for example, the IP addresses of the
30453 MX hosts or nameservers of an email sender address. For an example, see section
30454 &<<SECTmulkeyfor>>& below.
30459 .section "DNS lists keyed on domain names" "SECID202"
30460 .cindex "DNS list" "keyed by domain name"
30461 There are some lists that are keyed on domain names rather than inverted IP
30462 addresses (see for example the &'domain based zones'& link at
30463 &url(http://www.rfc-ignorant.org/)). No reversing of components is used
30464 with these lists. You can change the name that is looked up in a DNS list by
30465 listing it after the domain name, introduced by a slash. For example,
30467 deny message = Sender's domain is listed at $dnslist_domain
30468 dnslists = dsn.rfc-ignorant.org/$sender_address_domain
30470 This particular example is useful only in ACLs that are obeyed after the
30471 RCPT or DATA commands, when a sender address is available. If (for
30472 example) the message's sender is &'user@tld.example'& the name that is looked
30473 up by this example is
30475 tld.example.dsn.rfc-ignorant.org
30477 A single &%dnslists%& condition can contain entries for both names and IP
30478 addresses. For example:
30480 deny dnslists = sbl.spamhaus.org : \
30481 dsn.rfc-ignorant.org/$sender_address_domain
30483 The first item checks the sending host's IP address; the second checks a domain
30484 name. The whole condition is true if either of the DNS lookups succeeds.
30489 .section "Multiple explicit keys for a DNS list" "SECTmulkeyfor"
30490 .cindex "DNS list" "multiple keys for"
30491 The syntax described above for looking up explicitly-defined values (either
30492 names or IP addresses) in a DNS blacklist is a simplification. After the domain
30493 name for the DNS list, what follows the slash can in fact be a list of items.
30494 As with all lists in Exim, the default separator is a colon. However, because
30495 this is a sublist within the list of DNS blacklist domains, it is necessary
30496 either to double the separators like this:
30498 dnslists = black.list.tld/name.1::name.2
30500 or to change the separator character, like this:
30502 dnslists = black.list.tld/<;name.1;name.2
30504 If an item in the list is an IP address, it is inverted before the DNS
30505 blacklist domain is appended. If it is not an IP address, no inversion
30506 occurs. Consider this condition:
30508 dnslists = black.list.tld/<;192.168.1.2;a.domain
30510 The DNS lookups that occur are:
30512 2.1.168.192.black.list.tld
30513 a.domain.black.list.tld
30515 Once a DNS record has been found (that matches a specific IP return
30516 address, if specified &-- see section &<<SECTaddmatcon>>&), no further lookups
30517 are done. If there is a temporary DNS error, the rest of the sublist of domains
30518 or IP addresses is tried. A temporary error for the whole dnslists item occurs
30519 only if no other DNS lookup in this sublist succeeds. In other words, a
30520 successful lookup for any of the items in the sublist overrides a temporary
30521 error for a previous item.
30523 The ability to supply a list of items after the slash is in some sense just a
30524 syntactic convenience. These two examples have the same effect:
30526 dnslists = black.list.tld/a.domain : black.list.tld/b.domain
30527 dnslists = black.list.tld/a.domain::b.domain
30529 However, when the data for the list is obtained from a lookup, the second form
30530 is usually much more convenient. Consider this example:
30532 deny message = The mail servers for the domain \
30533 $sender_address_domain \
30534 are listed at $dnslist_domain ($dnslist_value); \
30536 dnslists = sbl.spamhaus.org/<|${lookup dnsdb {>|a=<|\
30537 ${lookup dnsdb {>|mxh=\
30538 $sender_address_domain} }} }
30540 Note the use of &`>|`& in the dnsdb lookup to specify the separator for
30541 multiple DNS records. The inner dnsdb lookup produces a list of MX hosts
30542 and the outer dnsdb lookup finds the IP addresses for these hosts. The result
30543 of expanding the condition might be something like this:
30545 dnslists = sbl.spamhaus.org/<|192.168.2.3|192.168.5.6|...
30547 Thus, this example checks whether or not the IP addresses of the sender
30548 domain's mail servers are on the Spamhaus black list.
30550 The key that was used for a successful DNS list lookup is put into the variable
30551 &$dnslist_matched$& (see section &<<SECID204>>&).
30556 .section "Data returned by DNS lists" "SECID203"
30557 .cindex "DNS list" "data returned from"
30558 DNS lists are constructed using address records in the DNS. The original RBL
30559 just used the address 127.0.0.1 on the right hand side of each record, but the
30560 RBL+ list and some other lists use a number of values with different meanings.
30561 The values used on the RBL+ list are:
30565 127.1.0.3 DUL and RBL
30567 127.1.0.5 RSS and RBL
30568 127.1.0.6 RSS and DUL
30569 127.1.0.7 RSS and DUL and RBL
30571 Section &<<SECTaddmatcon>>& below describes how you can distinguish between
30572 different values. Some DNS lists may return more than one address record;
30573 see section &<<SECThanmuldnsrec>>& for details of how they are checked.
30576 .section "Variables set from DNS lists" "SECID204"
30577 .cindex "expansion" "variables, set from DNS list"
30578 .cindex "DNS list" "variables set from"
30579 .vindex "&$dnslist_domain$&"
30580 .vindex "&$dnslist_matched$&"
30581 .vindex "&$dnslist_text$&"
30582 .vindex "&$dnslist_value$&"
30583 When an entry is found in a DNS list, the variable &$dnslist_domain$& contains
30584 the name of the overall domain that matched (for example,
30585 &`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain
30586 (for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from
30587 the DNS record. When the key is an IP address, it is not reversed in
30588 &$dnslist_matched$& (though it is, of course, in the actual lookup). In simple
30589 cases, for example:
30591 deny dnslists = spamhaus.example
30593 the key is also available in another variable (in this case,
30594 &$sender_host_address$&). In more complicated cases, however, this is not true.
30595 For example, using a data lookup (as described in section &<<SECTmulkeyfor>>&)
30596 might generate a dnslists lookup like this:
30598 deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
30600 If this condition succeeds, the value in &$dnslist_matched$& might be
30601 &`192.168.6.7`& (for example).
30603 If more than one address record is returned by the DNS lookup, all the IP
30604 addresses are included in &$dnslist_value$&, separated by commas and spaces.
30605 The variable &$dnslist_text$& contains the contents of any associated TXT
30606 record. For lists such as RBL+ the TXT record for a merged entry is often not
30607 very meaningful. See section &<<SECTmordetinf>>& for a way of obtaining more
30610 You can use the DNS list variables in &%message%& or &%log_message%& modifiers
30611 &-- although these appear before the condition in the ACL, they are not
30612 expanded until after it has failed. For example:
30614 deny hosts = !+local_networks
30615 message = $sender_host_address is listed \
30617 dnslists = rbl-plus.mail-abuse.example
30622 .section "Additional matching conditions for DNS lists" "SECTaddmatcon"
30623 .cindex "DNS list" "matching specific returned data"
30624 You can add an equals sign and an IP address after a &%dnslists%& domain name
30625 in order to restrict its action to DNS records with a matching right hand side.
30628 deny dnslists = rblplus.mail-abuse.org=127.0.0.2
30630 rejects only those hosts that yield 127.0.0.2. Without this additional data,
30631 any address record is considered to be a match. For the moment, we assume
30632 that the DNS lookup returns just one record. Section &<<SECThanmuldnsrec>>&
30633 describes how multiple records are handled.
30635 More than one IP address may be given for checking, using a comma as a
30636 separator. These are alternatives &-- if any one of them matches, the
30637 &%dnslists%& condition is true. For example:
30639 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
30641 If you want to specify a constraining address list and also specify names or IP
30642 addresses to be looked up, the constraining address list must be specified
30643 first. For example:
30645 deny dnslists = dsn.rfc-ignorant.org\
30646 =127.0.0.2/$sender_address_domain
30649 If the character &`&&`& is used instead of &`=`&, the comparison for each
30650 listed IP address is done by a bitwise &"and"& instead of by an equality test.
30651 In other words, the listed addresses are used as bit masks. The comparison is
30652 true if all the bits in the mask are present in the address that is being
30653 tested. For example:
30655 dnslists = a.b.c&0.0.0.3
30657 matches if the address is &'x.x.x.'&3, &'x.x.x.'&7, &'x.x.x.'&11, etc. If you
30658 want to test whether one bit or another bit is present (as opposed to both
30659 being present), you must use multiple values. For example:
30661 dnslists = a.b.c&0.0.0.1,0.0.0.2
30663 matches if the final component of the address is an odd number or two times
30668 .section "Negated DNS matching conditions" "SECID205"
30669 You can supply a negative list of IP addresses as part of a &%dnslists%&
30672 deny dnslists = a.b.c=127.0.0.2,127.0.0.3
30674 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
30675 IP address yielded by the list is either 127.0.0.2 or 127.0.0.3"&,
30677 deny dnslists = a.b.c!=127.0.0.2,127.0.0.3
30679 means &"deny if the host is in the black list at the domain &'a.b.c'& and the
30680 IP address yielded by the list is not 127.0.0.2 and not 127.0.0.3"&. In other
30681 words, the result of the test is inverted if an exclamation mark appears before
30682 the &`=`& (or the &`&&`&) sign.
30684 &*Note*&: This kind of negation is not the same as negation in a domain,
30685 host, or address list (which is why the syntax is different).
30687 If you are using just one list, the negation syntax does not gain you much. The
30688 previous example is precisely equivalent to
30690 deny dnslists = a.b.c
30691 !dnslists = a.b.c=127.0.0.2,127.0.0.3
30693 However, if you are using multiple lists, the negation syntax is clearer.
30694 Consider this example:
30696 deny dnslists = sbl.spamhaus.org : \
30698 dnsbl.njabl.org!=127.0.0.3 : \
30701 Using only positive lists, this would have to be:
30703 deny dnslists = sbl.spamhaus.org : \
30705 deny dnslists = dnsbl.njabl.org
30706 !dnslists = dnsbl.njabl.org=127.0.0.3
30707 deny dnslists = relays.ordb.org
30709 which is less clear, and harder to maintain.
30714 .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec"
30715 A DNS lookup for a &%dnslists%& condition may return more than one DNS record,
30716 thereby providing more than one IP address. When an item in a &%dnslists%& list
30717 is followed by &`=`& or &`&&`& and a list of IP addresses, in order to restrict
30718 the match to specific results from the DNS lookup, there are two ways in which
30719 the checking can be handled. For example, consider the condition:
30721 dnslists = a.b.c=127.0.0.1
30723 What happens if the DNS lookup for the incoming IP address yields both
30724 127.0.0.1 and 127.0.0.2 by means of two separate DNS records? Is the
30725 condition true because at least one given value was found, or is it false
30726 because at least one of the found values was not listed? And how does this
30727 affect negated conditions? Both possibilities are provided for with the help of
30728 additional separators &`==`& and &`=&&`&.
30731 If &`=`& or &`&&`& is used, the condition is true if any one of the looked up
30732 IP addresses matches one of the listed addresses. For the example above, the
30733 condition is true because 127.0.0.1 matches.
30735 If &`==`& or &`=&&`& is used, the condition is true only if every one of the
30736 looked up IP addresses matches one of the listed addresses. If the condition is
30739 dnslists = a.b.c==127.0.0.1
30741 and the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
30742 false because 127.0.0.2 is not listed. You would need to have:
30744 dnslists = a.b.c==127.0.0.1,127.0.0.2
30746 for the condition to be true.
30749 When &`!`& is used to negate IP address matching, it inverts the result, giving
30750 the precise opposite of the behaviour above. Thus:
30752 If &`!=`& or &`!&&`& is used, the condition is true if none of the looked up IP
30753 addresses matches one of the listed addresses. Consider:
30755 dnslists = a.b.c!&0.0.0.1
30757 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
30758 false because 127.0.0.1 matches.
30760 If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one
30761 looked up IP address that does not match. Consider:
30763 dnslists = a.b.c!=&0.0.0.1
30765 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is
30766 true, because 127.0.0.2 does not match. You would need to have:
30768 dnslists = a.b.c!=&0.0.0.1,0.0.0.2
30770 for the condition to be false.
30772 When the DNS lookup yields only a single IP address, there is no difference
30773 between &`=`& and &`==`& and between &`&&`& and &`=&&`&.
30778 .section "Detailed information from merged DNS lists" "SECTmordetinf"
30779 .cindex "DNS list" "information from merged"
30780 When the facility for restricting the matching IP values in a DNS list is used,
30781 the text from the TXT record that is set in &$dnslist_text$& may not reflect
30782 the true reason for rejection. This happens when lists are merged and the IP
30783 address in the A record is used to distinguish them; unfortunately there is
30784 only one TXT record. One way round this is not to use merged lists, but that
30785 can be inefficient because it requires multiple DNS lookups where one would do
30786 in the vast majority of cases when the host of interest is not on any of the
30789 A less inefficient way of solving this problem is available. If
30790 two domain names, comma-separated, are given, the second is used first to
30791 do an initial check, making use of any IP value restrictions that are set.
30792 If there is a match, the first domain is used, without any IP value
30793 restrictions, to get the TXT record. As a byproduct of this, there is also
30794 a check that the IP being tested is indeed on the first list. The first
30795 domain is the one that is put in &$dnslist_domain$&. For example:
30798 rejected because $sender_host_address is blacklisted \
30799 at $dnslist_domain\n$dnslist_text
30801 sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
30802 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
30804 For the first blacklist item, this starts by doing a lookup in
30805 &'sbl-xbl.spamhaus.org'& and testing for a 127.0.0.2 return. If there is a
30806 match, it then looks in &'sbl.spamhaus.org'&, without checking the return
30807 value, and as long as something is found, it looks for the corresponding TXT
30808 record. If there is no match in &'sbl-xbl.spamhaus.org'&, nothing more is done.
30809 The second blacklist item is processed similarly.
30811 If you are interested in more than one merged list, the same list must be
30812 given several times, but because the results of the DNS lookups are cached,
30813 the DNS calls themselves are not repeated. For example:
30816 http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
30817 socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
30818 misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
30819 dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
30821 In this case there is one lookup in &'dnsbl.sorbs.net'&, and if none of the IP
30822 values matches (or if no record is found), this is the only lookup that is
30823 done. Only if there is a match is one of the more specific lists consulted.
30827 .section "DNS lists and IPv6" "SECTmorednslistslast"
30828 .cindex "IPv6" "DNS black lists"
30829 .cindex "DNS list" "IPv6 usage"
30830 If Exim is asked to do a dnslist lookup for an IPv6 address, it inverts it
30831 nibble by nibble. For example, if the calling host's IP address is
30832 3ffe:ffff:836f:0a00:000a:0800:200a:c031, Exim might look up
30834 1.3.0.c.a.0.0.2.0.0.8.0.a.0.0.0.0.0.a.0.f.6.3.8.
30835 f.f.f.f.e.f.f.3.blackholes.mail-abuse.org
30837 (split over two lines here to fit on the page). Unfortunately, some of the DNS
30838 lists contain wildcard records, intended for IPv4, that interact badly with
30839 IPv6. For example, the DNS entry
30841 *.3.some.list.example. A 127.0.0.1
30843 is probably intended to put the entire 3.0.0.0/8 IPv4 network on the list.
30844 Unfortunately, it also matches the entire 3::/4 IPv6 network.
30846 You can exclude IPv6 addresses from DNS lookups by making use of a suitable
30847 &%condition%& condition, as in this example:
30849 deny condition = ${if isip4{$sender_host_address}}
30850 dnslists = some.list.example
30853 If an explicit key is being used for a DNS lookup and it may be an IPv6
30854 address you should specify alternate list separators for both the outer
30855 (DNS list name) list and inner (lookup keys) list:
30857 dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
30860 .section "Rate limiting incoming messages" "SECTratelimiting"
30861 .cindex "rate limiting" "client sending"
30862 .cindex "limiting client sending rates"
30863 .oindex "&%smtp_ratelimit_*%&"
30864 The &%ratelimit%& ACL condition can be used to measure and control the rate at
30865 which clients can send email. This is more powerful than the
30866 &%smtp_ratelimit_*%& options, because those options control the rate of
30867 commands in a single SMTP session only, whereas the &%ratelimit%& condition
30868 works across all connections (concurrent and sequential) from the same client
30869 host. The syntax of the &%ratelimit%& condition is:
30871 &`ratelimit =`& <&'m'&> &`/`& <&'p'&> &`/`& <&'options'&> &`/`& <&'key'&>
30873 If the average client sending rate is less than &'m'& messages per time
30874 period &'p'& then the condition is false; otherwise it is true.
30876 As a side-effect, the &%ratelimit%& condition sets the expansion variable
30877 &$sender_rate$& to the client's computed rate, &$sender_rate_limit$& to the
30878 configured value of &'m'&, and &$sender_rate_period$& to the configured value
30881 The parameter &'p'& is the smoothing time constant, in the form of an Exim
30882 time interval, for example, &`8h`& for eight hours. A larger time constant
30883 means that it takes Exim longer to forget a client's past behaviour. The
30884 parameter &'m'& is the maximum number of messages that a client is permitted to
30885 send in each time interval. It also specifies the number of messages permitted
30886 in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'&
30887 constant, you can allow a client to send more messages in a burst without
30888 changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are
30889 both small, messages must be sent at an even rate.
30891 There is a script in &_util/ratelimit.pl_& which extracts sending rates from
30892 log files, to assist with choosing appropriate settings for &'m'& and &'p'&
30893 when deploying the &%ratelimit%& ACL condition. The script prints usage
30894 instructions when it is run with no arguments.
30896 The key is used to look up the data for calculating the client's average
30897 sending rate. This data is stored in Exim's spool directory, alongside the
30898 retry and other hints databases. The default key is &$sender_host_address$&,
30899 which means Exim computes the sending rate of each client host IP address.
30900 By changing the key you can change how Exim identifies clients for the purpose
30901 of ratelimiting. For example, to limit the sending rate of each authenticated
30902 user, independent of the computer they are sending from, set the key to
30903 &$authenticated_id$&. You must ensure that the lookup key is meaningful; for
30904 example, &$authenticated_id$& is only meaningful if the client has
30905 authenticated (which you can check with the &%authenticated%& ACL condition).
30907 The lookup key does not have to identify clients: If you want to limit the
30908 rate at which a recipient receives messages, you can use the key
30909 &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT
30912 Each &%ratelimit%& condition can have up to four options. A &%per_*%& option
30913 specifies what Exim measures the rate of, for example messages or recipients
30914 or bytes. You can adjust the measurement using the &%unique=%& and/or
30915 &%count=%& options. You can also control when Exim updates the recorded rate
30916 using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are
30917 separated by a slash, like the other parameters. They may appear in any order.
30919 Internally, Exim appends the smoothing constant &'p'& onto the lookup key with
30920 any options that alter the meaning of the stored data. The limit &'m'& is not
30921 stored, so you can alter the configured maximum rate and Exim will still
30922 remember clients' past behaviour. If you change the &%per_*%& mode or add or
30923 remove the &%unique=%& option, the lookup key changes so Exim will forget past
30924 behaviour. The lookup key is not affected by changes to the update mode and
30925 the &%count=%& option.
30928 .section "Ratelimit options for what is being measured" "ratoptmea"
30929 .cindex "rate limiting" "per_* options"
30930 The &%per_conn%& option limits the client's connection rate. It is not
30931 normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or
30932 &%acl_not_smtp_start%& ACLs.
30934 The &%per_mail%& option limits the client's rate of sending messages. This is
30935 the default if none of the &%per_*%& options is specified. It can be used in
30936 &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&,
30937 &%acl_smtp_data%&, or &%acl_not_smtp%&.
30939 The &%per_byte%& option limits the sender's email bandwidth. It can be used in
30940 the same ACLs as the &%per_mail%& option, though it is best to use this option
30941 in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is
30942 used in an earlier ACL, Exim relies on the SIZE parameter given by the client
30943 in its MAIL command, which may be inaccurate or completely missing. You can
30944 follow the limit &'m'& in the configuration with K, M, or G to specify limits
30945 in kilobytes, megabytes, or gigabytes, respectively.
30947 The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
30948 accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
30949 &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
30950 &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
30951 ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
30952 in either case the rate limiting engine will see a message with many
30953 recipients as a large high-speed burst.
30955 The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the
30956 number of different recipients that the client has sent messages to in the
30957 last time period. That is, if the client repeatedly sends messages to the same
30958 recipient, its measured rate is not increased. This option can only be used in
30961 The &%per_cmd%& option causes Exim to recompute the rate every time the
30962 condition is processed. This can be used to limit the rate of any SMTP
30963 command. If it is used in multiple ACLs it can limit the aggregate rate of
30964 multiple different commands.
30966 The &%count=%& option can be used to alter how much Exim adds to the client's
30967 measured rate. For example, the &%per_byte%& option is equivalent to
30968 &`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim
30969 increases the measured rate by one (except for the &%per_rcpt%& option in ACLs
30970 other than &%acl_smtp_rcpt%&). The count does not have to be an integer.
30972 The &%unique=%& option is described in section &<<ratoptuniq>>& below.
30975 .section "Ratelimit update modes" "ratoptupd"
30976 .cindex "rate limiting" "reading data without updating"
30977 You can specify one of three options with the &%ratelimit%& condition to
30978 control when its database is updated. This section describes the &%readonly%&
30979 mode, and the next section describes the &%strict%& and &%leaky%& modes.
30981 If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a
30982 previously-computed rate to check against the limit.
30984 For example, you can test the client's sending rate and deny it access (when
30985 it is too fast) in the connect ACL. If the client passes this check then it
30986 can go on to send a message, in which case its recorded rate will be updated
30987 in the MAIL ACL. Subsequent connections from the same client will check this
30991 deny ratelimit = 100 / 5m / readonly
30992 log_message = RATE CHECK: $sender_rate/$sender_rate_period \
30993 (max $sender_rate_limit)
30996 warn ratelimit = 100 / 5m / strict
30997 log_message = RATE UPDATE: $sender_rate/$sender_rate_period \
30998 (max $sender_rate_limit)
31001 If Exim encounters multiple &%ratelimit%& conditions with the same key when
31002 processing a message then it may increase the client's measured rate more than
31003 it should. For example, this will happen if you check the &%per_rcpt%& option
31004 in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the
31005 same &%ratelimit%& condition multiple times in the same ACL. You can avoid any
31006 multiple update problems by using the &%readonly%& option on later ratelimit
31009 The &%per_*%& options described above do not make sense in some ACLs. If you
31010 use a &%per_*%& option in an ACL where it is not normally permitted then the
31011 update mode defaults to &%readonly%& and you cannot specify the &%strict%& or
31012 &%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the
31013 next section) so you must specify the &%readonly%& option explicitly.
31016 .section "Ratelimit options for handling fast clients" "ratoptfast"
31017 .cindex "rate limiting" "strict and leaky modes"
31018 If a client's average rate is greater than the maximum, the rate limiting
31019 engine can react in two possible ways, depending on the presence of the
31020 &%strict%& or &%leaky%& update modes. This is independent of the other
31021 counter-measures (such as rejecting the message) that may be specified by the
31024 The &%leaky%& (default) option means that the client's recorded rate is not
31025 updated if it is above the limit. The effect of this is that Exim measures the
31026 client's average rate of successfully sent email,
31028 up to the given limit.
31029 This is appropriate if the countermeasure when the condition is true
31030 consists of refusing the message, and
31031 is generally the better choice if you have clients that retry automatically.
31032 If the action when true is anything more complex then this option is
31033 likely not what is wanted.
31036 The &%strict%& option means that the client's recorded rate is always
31037 updated. The effect of this is that Exim measures the client's average rate
31038 of attempts to send email, which can be much higher than the maximum it is
31039 actually allowed. If the client is over the limit it may be subjected to
31040 counter-measures by the ACL. It must slow down and allow sufficient time to
31041 pass that its computed rate falls below the maximum before it can send email
31042 again. The time (the number of smoothing periods) it must wait and not
31043 attempt to send mail can be calculated with this formula:
31045 ln(peakrate/maxrate)
31049 .section "Limiting the rate of different events" "ratoptuniq"
31050 .cindex "rate limiting" "counting unique events"
31051 The &%ratelimit%& &%unique=%& option controls a mechanism for counting the
31052 rate of different events. For example, the &%per_addr%& option uses this
31053 mechanism to count the number of different recipients that the client has
31054 sent messages to in the last time period; it is equivalent to
31055 &`per_rcpt/unique=$local_part@$domain`&. You could use this feature to
31056 measure the rate that a client uses different sender addresses with the
31057 options &`per_mail/unique=$sender_address`&.
31059 For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it
31060 has seen for that key. The whole set is thrown away when it is older than the
31061 rate smoothing period &'p'&, so each different event is counted at most once
31062 per period. In the &%leaky%& update mode, an event that causes the client to
31063 go over the limit is not added to the set, in the same way that the client's
31064 recorded rate is not updated in the same situation.
31066 When you combine the &%unique=%& and &%readonly%& options, the specific
31067 &%unique=%& value is ignored, and Exim just retrieves the client's stored
31070 The &%unique=%& mechanism needs more space in the ratelimit database than the
31071 other &%ratelimit%& options in order to store the event set. The number of
31072 unique values is potentially as large as the rate limit, so the extra space
31073 required increases with larger limits.
31075 The uniqueification is not perfect: there is a small probability that Exim
31076 will think a new event has happened before. If the sender's rate is less than
31077 the limit, Exim should be more than 99.9% correct. However in &%strict%& mode
31078 the measured rate can go above the limit, in which case Exim may under-count
31079 events by a significant margin. Fortunately, if the rate is high enough (2.7
31080 times the limit) that the false positive rate goes above 9%, then Exim will
31081 throw away the over-full event set before the measured rate falls below the
31082 limit. Therefore the only harm should be that exceptionally high sending rates
31083 are logged incorrectly; any countermeasures you configure will be as effective
31087 .section "Using rate limiting" "useratlim"
31088 Exim's other ACL facilities are used to define what counter-measures are taken
31089 when the rate limit is exceeded. This might be anything from logging a warning
31090 (for example, while measuring existing sending rates in order to define
31091 policy), through time delays to slow down fast senders, up to rejecting the
31092 message. For example:
31094 # Log all senders' rates
31095 warn ratelimit = 0 / 1h / strict
31096 log_message = Sender rate $sender_rate / $sender_rate_period
31098 # Slow down fast senders; note the need to truncate $sender_rate
31099 # at the decimal point.
31100 warn ratelimit = 100 / 1h / per_rcpt / strict
31101 delay = ${eval: ${sg{$sender_rate}{[.].*}{}} - \
31102 $sender_rate_limit }s
31104 # Keep authenticated users under control
31105 deny authenticated = *
31106 ratelimit = 100 / 1d / strict / $authenticated_id
31108 # System-wide rate limit
31109 defer message = Sorry, too busy. Try again later.
31110 ratelimit = 10 / 1s / $primary_hostname
31112 # Restrict incoming rate from each host, with a default
31113 # set using a macro and special cases looked up in a table.
31114 defer message = Sender rate exceeds $sender_rate_limit \
31115 messages per $sender_rate_period
31116 ratelimit = ${lookup {$sender_host_address} \
31117 cdb {DB/ratelimits.cdb} \
31118 {$value} {RATELIMIT} }
31120 &*Warning*&: If you have a busy server with a lot of &%ratelimit%& tests,
31121 especially with the &%per_rcpt%& option, you may suffer from a performance
31122 bottleneck caused by locking on the ratelimit hints database. Apart from
31123 making your ACLs less complicated, you can reduce the problem by using a
31124 RAM disk for Exim's hints directory (usually &_/var/spool/exim/db/_&). However
31125 this means that Exim will lose its hints data after a reboot (including retry
31126 hints, the callout cache, and ratelimit data).
31130 .section "Address verification" "SECTaddressverification"
31131 .cindex "verifying address" "options for"
31132 .cindex "policy control" "address verification"
31133 Several of the &%verify%& conditions described in section
31134 &<<SECTaclconditions>>& cause addresses to be verified. Section
31135 &<<SECTsenaddver>>& discusses the reporting of sender verification failures.
31136 The verification conditions can be followed by options that modify the
31137 verification process. The options are separated from the keyword and from each
31138 other by slashes, and some of them contain parameters. For example:
31140 verify = sender/callout
31141 verify = recipient/defer_ok/callout=10s,defer_ok
31143 The first stage of address verification, which always happens, is to run the
31144 address through the routers, in &"verify mode"&. Routers can detect the
31145 difference between verification and routing for delivery, and their actions can
31146 be varied by a number of generic options such as &%verify%& and &%verify_only%&
31147 (see chapter &<<CHAProutergeneric>>&). If routing fails, verification fails.
31148 The available options are as follows:
31151 If the &%callout%& option is specified, successful routing to one or more
31152 remote hosts is followed by a &"callout"& to those hosts as an additional
31153 check. Callouts and their sub-options are discussed in the next section.
31155 If there is a defer error while doing verification routing, the ACL
31156 normally returns &"defer"&. However, if you include &%defer_ok%& in the
31157 options, the condition is forced to be true instead. Note that this is a main
31158 verification option as well as a suboption for callouts.
31160 The &%no_details%& option is covered in section &<<SECTsenaddver>>&, which
31161 discusses the reporting of sender address verification failures.
31163 The &%success_on_redirect%& option causes verification always to succeed
31164 immediately after a successful redirection. By default, if a redirection
31165 generates just one address, that address is also verified. See further
31166 discussion in section &<<SECTredirwhilveri>>&.
31169 .cindex "verifying address" "differentiating failures"
31170 .vindex "&$recipient_verify_failure$&"
31171 .vindex "&$sender_verify_failure$&"
31172 .vindex "&$acl_verify_message$&"
31173 After an address verification failure, &$acl_verify_message$& contains the
31174 error message that is associated with the failure. It can be preserved by
31177 warn !verify = sender
31178 set acl_m0 = $acl_verify_message
31180 If you are writing your own custom rejection message or log message when
31181 denying access, you can use this variable to include information about the
31182 verification failure.
31184 In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
31185 appropriate) contains one of the following words:
31188 &%qualify%&: The address was unqualified (no domain), and the message
31189 was neither local nor came from an exempted host.
31191 &%route%&: Routing failed.
31193 &%mail%&: Routing succeeded, and a callout was attempted; rejection
31194 occurred at or before the MAIL command (that is, on initial
31195 connection, HELO, or MAIL).
31197 &%recipient%&: The RCPT command in a callout was rejected.
31199 &%postmaster%&: The postmaster check in a callout was rejected.
31202 The main use of these variables is expected to be to distinguish between
31203 rejections of MAIL and rejections of RCPT in callouts.
31206 The above variables may also be set after a &*successful*&
31207 address verification to:
31210 &%random%&: A random local-part callout succeeded
31217 .section "Callout verification" "SECTcallver"
31218 .cindex "verifying address" "by callout"
31219 .cindex "callout" "verification"
31220 .cindex "SMTP" "callout verification"
31221 For non-local addresses, routing verifies the domain, but is unable to do any
31222 checking of the local part. There are situations where some means of verifying
31223 the local part is desirable. One way this can be done is to make an SMTP
31224 &'callback'& to a delivery host for the sender address or a &'callforward'& to
31225 a subsequent host for a recipient address, to see if the host accepts the
31226 address. We use the term &'callout'& to cover both cases. Note that for a
31227 sender address, the callback is not to the client host that is trying to
31228 deliver the message, but to one of the hosts that accepts incoming mail for the
31231 Exim does not do callouts by default. If you want them to happen, you must
31232 request them by setting appropriate options on the &%verify%& condition, as
31233 described below. This facility should be used with care, because it can add a
31234 lot of resource usage to the cost of verifying an address. However, Exim does
31235 cache the results of callouts, which helps to reduce the cost. Details of
31236 caching are in section &<<SECTcallvercache>>&.
31238 Recipient callouts are usually used only between hosts that are controlled by
31239 the same administration. For example, a corporate gateway host could use
31240 callouts to check for valid recipients on an internal mailserver. A successful
31241 callout does not guarantee that a real delivery to the address would succeed;
31242 on the other hand, a failing callout does guarantee that a delivery would fail.
31244 If the &%callout%& option is present on a condition that verifies an address, a
31245 second stage of verification occurs if the address is successfully routed to
31246 one or more remote hosts. The usual case is routing by a &(dnslookup)& or a
31247 &(manualroute)& router, where the router specifies the hosts. However, if a
31248 router that does not set up hosts routes to an &(smtp)& transport with a
31249 &%hosts%& setting, the transport's hosts are used. If an &(smtp)& transport has
31250 &%hosts_override%& set, its hosts are always used, whether or not the router
31251 supplies a host list.
31252 Callouts are only supported on &(smtp)& transports.
31254 The port that is used is taken from the transport, if it is specified and is a
31255 remote transport. (For routers that do verification only, no transport need be
31256 specified.) Otherwise, the default SMTP port is used. If a remote transport
31257 specifies an outgoing interface, this is used; otherwise the interface is not
31258 specified. Likewise, the text that is used for the HELO command is taken from
31259 the transport's &%helo_data%& option; if there is no transport, the value of
31260 &$smtp_active_hostname$& is used.
31262 For a sender callout check, Exim makes SMTP connections to the remote hosts, to
31263 test whether a bounce message could be delivered to the sender address. The
31264 following SMTP commands are sent:
31266 &`HELO `&<&'local host name'&>
31268 &`RCPT TO:`&<&'the address to be tested'&>
31271 LHLO is used instead of HELO if the transport's &%protocol%& option is
31274 The callout may use EHLO, AUTH and/or STARTTLS given appropriate option
31277 A recipient callout check is similar. By default, it also uses an empty address
31278 for the sender. This default is chosen because most hosts do not make use of
31279 the sender address when verifying a recipient. Using the same address means
31280 that a single cache entry can be used for each recipient. Some sites, however,
31281 do make use of the sender address when verifying. These are catered for by the
31282 &%use_sender%& and &%use_postmaster%& options, described in the next section.
31284 If the response to the RCPT command is a 2&'xx'& code, the verification
31285 succeeds. If it is 5&'xx'&, the verification fails. For any other condition,
31286 Exim tries the next host, if any. If there is a problem with all the remote
31287 hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the
31288 &%callout%& option is given, in which case the condition is forced to succeed.
31290 .cindex "SMTP" "output flushing, disabling for callout"
31291 A callout may take a little time. For this reason, Exim normally flushes SMTP
31292 output before performing a callout in an ACL, to avoid unexpected timeouts in
31293 clients when the SMTP PIPELINING extension is in use. The flushing can be
31294 disabled by using a &%control%& modifier to set &%no_callout_flush%&.
31299 .section "Additional parameters for callouts" "CALLaddparcall"
31300 .cindex "callout" "additional parameters for"
31301 The &%callout%& option can be followed by an equals sign and a number of
31302 optional parameters, separated by commas. For example:
31304 verify = recipient/callout=10s,defer_ok
31306 The old syntax, which had &%callout_defer_ok%& and &%check_postmaster%& as
31307 separate verify options, is retained for backwards compatibility, but is now
31308 deprecated. The additional parameters for &%callout%& are as follows:
31312 .vitem <&'a&~time&~interval'&>
31313 .cindex "callout" "timeout, specifying"
31314 This specifies the timeout that applies for the callout attempt to each host.
31317 verify = sender/callout=5s
31319 The default is 30 seconds. The timeout is used for each response from the
31320 remote host. It is also used for the initial connection, unless overridden by
31321 the &%connect%& parameter.
31324 .vitem &*connect&~=&~*&<&'time&~interval'&>
31325 .cindex "callout" "connection timeout, specifying"
31326 This parameter makes it possible to set a different (usually smaller) timeout
31327 for making the SMTP connection. For example:
31329 verify = sender/callout=5s,connect=1s
31331 If not specified, this timeout defaults to the general timeout value.
31333 .vitem &*defer_ok*&
31334 .cindex "callout" "defer, action on"
31335 When this parameter is present, failure to contact any host, or any other kind
31336 of temporary error, is treated as success by the ACL. However, the cache is not
31337 updated in this circumstance.
31339 .vitem &*fullpostmaster*&
31340 .cindex "callout" "full postmaster check"
31341 This operates like the &%postmaster%& option (see below), but if the check for
31342 &'postmaster@domain'& fails, it tries just &'postmaster'&, without a domain, in
31343 accordance with the specification in RFC 2821. The RFC states that the
31344 unqualified address &'postmaster'& should be accepted.
31347 .vitem &*mailfrom&~=&~*&<&'email&~address'&>
31348 .cindex "callout" "sender when verifying header"
31349 When verifying addresses in header lines using the &%header_sender%&
31350 verification option, Exim behaves by default as if the addresses are envelope
31351 sender addresses from a message. Callout verification therefore tests to see
31352 whether a bounce message could be delivered, by using an empty address in the
31353 MAIL command. However, it is arguable that these addresses might never be used
31354 as envelope senders, and could therefore justifiably reject bounce messages
31355 (empty senders). The &%mailfrom%& callout parameter allows you to specify what
31356 address to use in the MAIL command. For example:
31358 require verify = header_sender/callout=mailfrom=abcd@x.y.z
31360 This parameter is available only for the &%header_sender%& verification option.
31363 .vitem &*maxwait&~=&~*&<&'time&~interval'&>
31364 .cindex "callout" "overall timeout, specifying"
31365 This parameter sets an overall timeout for performing a callout verification.
31368 verify = sender/callout=5s,maxwait=30s
31370 This timeout defaults to four times the callout timeout for individual SMTP
31371 commands. The overall timeout applies when there is more than one host that can
31372 be tried. The timeout is checked before trying the next host. This prevents
31373 very long delays if there are a large number of hosts and all are timing out
31374 (for example, when network connections are timing out).
31377 .vitem &*no_cache*&
31378 .cindex "callout" "cache, suppressing"
31379 .cindex "caching callout, suppressing"
31380 When this parameter is given, the callout cache is neither read nor updated.
31382 .vitem &*postmaster*&
31383 .cindex "callout" "postmaster; checking"
31384 When this parameter is set, a successful callout check is followed by a similar
31385 check for the local part &'postmaster'& at the same domain. If this address is
31386 rejected, the callout fails (but see &%fullpostmaster%& above). The result of
31387 the postmaster check is recorded in a cache record; if it is a failure, this is
31388 used to fail subsequent callouts for the domain without a connection being
31389 made, until the cache record expires.
31391 .vitem &*postmaster_mailfrom&~=&~*&<&'email&~address'&>
31392 The postmaster check uses an empty sender in the MAIL command by default.
31393 You can use this parameter to do a postmaster check using a different address.
31396 require verify = sender/callout=postmaster_mailfrom=abc@x.y.z
31398 If both &%postmaster%& and &%postmaster_mailfrom%& are present, the rightmost
31399 one overrides. The &%postmaster%& parameter is equivalent to this example:
31401 require verify = sender/callout=postmaster_mailfrom=
31403 &*Warning*&: The caching arrangements for postmaster checking do not take
31404 account of the sender address. It is assumed that either the empty address or
31405 a fixed non-empty address will be used. All that Exim remembers is that the
31406 postmaster check for the domain succeeded or failed.
31410 .cindex "callout" "&""random""& check"
31411 When this parameter is set, before doing the normal callout check, Exim does a
31412 check for a &"random"& local part at the same domain. The local part is not
31413 really random &-- it is defined by the expansion of the option
31414 &%callout_random_local_part%&, which defaults to
31416 $primary_hostname-$tod_epoch-testing
31418 The idea here is to try to determine whether the remote host accepts all local
31419 parts without checking. If it does, there is no point in doing callouts for
31420 specific local parts. If the &"random"& check succeeds, the result is saved in
31421 a cache record, and used to force the current and subsequent callout checks to
31422 succeed without a connection being made, until the cache record expires.
31424 .vitem &*use_postmaster*&
31425 .cindex "callout" "sender for recipient check"
31426 This parameter applies to recipient callouts only. For example:
31428 deny !verify = recipient/callout=use_postmaster
31430 .vindex "&$qualify_domain$&"
31431 It causes a non-empty postmaster address to be used in the MAIL command when
31432 performing the callout for the recipient, and also for a &"random"& check if
31433 that is configured. The local part of the address is &`postmaster`& and the
31434 domain is the contents of &$qualify_domain$&.
31436 .vitem &*use_sender*&
31437 This option applies to recipient callouts only. For example:
31439 require verify = recipient/callout=use_sender
31441 It causes the message's actual sender address to be used in the MAIL
31442 command when performing the callout, instead of an empty address. There is no
31443 need to use this option unless you know that the called hosts make use of the
31444 sender when checking recipients. If used indiscriminately, it reduces the
31445 usefulness of callout caching.
31448 This option applies to recipient callouts only. For example:
31450 require verify = recipient/callout=use_sender,hold
31452 It causes the connection to be held open and used for any further recipients
31453 and for eventual delivery (should that be done quickly).
31454 Doing this saves on TCP and SMTP startup costs, and TLS costs also
31455 when that is used for the connections.
31456 The advantage is only gained if there are no callout cache hits
31457 (which could be enforced by the no_cache option),
31458 if the use_sender option is used,
31459 if neither the random nor the use_postmaster option is used,
31460 and if no other callouts intervene.
31463 If you use any of the parameters that set a non-empty sender for the MAIL
31464 command (&%mailfrom%&, &%postmaster_mailfrom%&, &%use_postmaster%&, or
31465 &%use_sender%&), you should think about possible loops. Recipient checking is
31466 usually done between two hosts that are under the same management, and the host
31467 that receives the callouts is not normally configured to do callouts itself.
31468 Therefore, it is normally safe to use &%use_postmaster%& or &%use_sender%& in
31469 these circumstances.
31471 However, if you use a non-empty sender address for a callout to an arbitrary
31472 host, there is the likelihood that the remote host will itself initiate a
31473 callout check back to your host. As it is checking what appears to be a message
31474 sender, it is likely to use an empty address in MAIL, thus avoiding a
31475 callout loop. However, to be on the safe side it would be best to set up your
31476 own ACLs so that they do not do sender verification checks when the recipient
31477 is the address you use for header sender or postmaster callout checking.
31479 Another issue to think about when using non-empty senders for callouts is
31480 caching. When you set &%mailfrom%& or &%use_sender%&, the cache record is keyed
31481 by the sender/recipient combination; thus, for any given recipient, many more
31482 actual callouts are performed than when an empty sender or postmaster is used.
31487 .section "Callout caching" "SECTcallvercache"
31488 .cindex "hints database" "callout cache"
31489 .cindex "callout" "cache, description of"
31490 .cindex "caching" "callout"
31491 Exim caches the results of callouts in order to reduce the amount of resources
31492 used, unless you specify the &%no_cache%& parameter with the &%callout%&
31493 option. A hints database called &"callout"& is used for the cache. Two
31494 different record types are used: one records the result of a callout check for
31495 a specific address, and the other records information that applies to the
31496 entire domain (for example, that it accepts the local part &'postmaster'&).
31498 When an original callout fails, a detailed SMTP error message is given about
31499 the failure. However, for subsequent failures use the cache data, this message
31502 The expiry times for negative and positive address cache records are
31503 independent, and can be set by the global options &%callout_negative_expire%&
31504 (default 2h) and &%callout_positive_expire%& (default 24h), respectively.
31506 If a host gives a negative response to an SMTP connection, or rejects any
31507 commands up to and including
31511 (but not including the MAIL command with a non-empty address),
31512 any callout attempt is bound to fail. Exim remembers such failures in a
31513 domain cache record, which it uses to fail callouts for the domain without
31514 making new connections, until the domain record times out. There are two
31515 separate expiry times for domain cache records:
31516 &%callout_domain_negative_expire%& (default 3h) and
31517 &%callout_domain_positive_expire%& (default 7d).
31519 Domain records expire when the negative expiry time is reached if callouts
31520 cannot be made for the domain, or if the postmaster check failed.
31521 Otherwise, they expire when the positive expiry time is reached. This
31522 ensures that, for example, a host that stops accepting &"random"& local parts
31523 will eventually be noticed.
31525 The callout caching mechanism is based on the domain of the address that is
31526 being tested. If the domain routes to several hosts, it is assumed that their
31527 behaviour will be the same.
31531 .section "Sender address verification reporting" "SECTsenaddver"
31532 .cindex "verifying" "suppressing error details"
31533 See section &<<SECTaddressverification>>& for a general discussion of
31534 verification. When sender verification fails in an ACL, the details of the
31535 failure are given as additional output lines before the 550 response to the
31536 relevant SMTP command (RCPT or DATA). For example, if sender callout is in use,
31539 MAIL FROM:<xyz@abc.example>
31541 RCPT TO:<pqr@def.example>
31542 550-Verification failed for <xyz@abc.example>
31543 550-Called: 192.168.34.43
31544 550-Sent: RCPT TO:<xyz@abc.example>
31545 550-Response: 550 Unknown local part xyz in <xyz@abc.example>
31546 550 Sender verification failed
31548 If more than one RCPT command fails in the same way, the details are given
31549 only for the first of them. However, some administrators do not want to send
31550 out this much information. You can suppress the details by adding
31551 &`/no_details`& to the ACL statement that requests sender verification. For
31554 verify = sender/no_details
31557 .section "Redirection while verifying" "SECTredirwhilveri"
31558 .cindex "verifying" "redirection while"
31559 .cindex "address redirection" "while verifying"
31560 A dilemma arises when a local address is redirected by aliasing or forwarding
31561 during verification: should the generated addresses themselves be verified,
31562 or should the successful expansion of the original address be enough to verify
31563 it? By default, Exim takes the following pragmatic approach:
31566 When an incoming address is redirected to just one child address, verification
31567 continues with the child address, and if that fails to verify, the original
31568 verification also fails.
31570 When an incoming address is redirected to more than one child address,
31571 verification does not continue. A success result is returned.
31574 This seems the most reasonable behaviour for the common use of aliasing as a
31575 way of redirecting different local parts to the same mailbox. It means, for
31576 example, that a pair of alias entries of the form
31579 aw123: :fail: Gone away, no forwarding address
31581 work as expected, with both local parts causing verification failure. When a
31582 redirection generates more than one address, the behaviour is more like a
31583 mailing list, where the existence of the alias itself is sufficient for
31584 verification to succeed.
31586 It is possible, however, to change the default behaviour so that all successful
31587 redirections count as successful verifications, however many new addresses are
31588 generated. This is specified by the &%success_on_redirect%& verification
31589 option. For example:
31591 require verify = recipient/success_on_redirect/callout=10s
31593 In this example, verification succeeds if a router generates a new address, and
31594 the callout does not occur, because no address was routed to a remote host.
31596 When verification is being tested via the &%-bv%& option, the treatment of
31597 redirections is as just described, unless the &%-v%& or any debugging option is
31598 also specified. In that case, full verification is done for every generated
31599 address and a report is output for each of them.
31603 .section "Client SMTP authorization (CSA)" "SECTverifyCSA"
31604 .cindex "CSA" "verifying"
31605 Client SMTP Authorization is a system that allows a site to advertise
31606 which machines are and are not permitted to send email. This is done by placing
31607 special SRV records in the DNS; these are looked up using the client's HELO
31608 domain. At the time of writing, CSA is still an Internet Draft. Client SMTP
31609 Authorization checks in Exim are performed by the ACL condition:
31613 This fails if the client is not authorized. If there is a DNS problem, or if no
31614 valid CSA SRV record is found, or if the client is authorized, the condition
31615 succeeds. These three cases can be distinguished using the expansion variable
31616 &$csa_status$&, which can take one of the values &"fail"&, &"defer"&,
31617 &"unknown"&, or &"ok"&. The condition does not itself defer because that would
31618 be likely to cause problems for legitimate email.
31620 The error messages produced by the CSA code include slightly more
31621 detail. If &$csa_status$& is &"defer"&, this may be because of problems
31622 looking up the CSA SRV record, or problems looking up the CSA target
31623 address record. There are four reasons for &$csa_status$& being &"fail"&:
31626 The client's host name is explicitly not authorized.
31628 The client's IP address does not match any of the CSA target IP addresses.
31630 The client's host name is authorized but it has no valid target IP addresses
31631 (for example, the target's addresses are IPv6 and the client is using IPv4).
31633 The client's host name has no CSA SRV record but a parent domain has asserted
31634 that all subdomains must be explicitly authorized.
31637 The &%csa%& verification condition can take an argument which is the domain to
31638 use for the DNS query. The default is:
31640 verify = csa/$sender_helo_name
31642 This implementation includes an extension to CSA. If the query domain
31643 is an address literal such as [192.0.2.95], or if it is a bare IP
31644 address, Exim searches for CSA SRV records in the reverse DNS as if
31645 the HELO domain was (for example) &'95.2.0.192.in-addr.arpa'&. Therefore it is
31648 verify = csa/$sender_host_address
31650 In fact, this is the check that Exim performs if the client does not say HELO.
31651 This extension can be turned off by setting the main configuration option
31652 &%dns_csa_use_reverse%& to be false.
31654 If a CSA SRV record is not found for the domain itself, a search
31655 is performed through its parent domains for a record which might be
31656 making assertions about subdomains. The maximum depth of this search is limited
31657 using the main configuration option &%dns_csa_search_limit%&, which is 5 by
31658 default. Exim does not look for CSA SRV records in a top level domain, so the
31659 default settings handle HELO domains as long as seven
31660 (&'hostname.five.four.three.two.one.com'&). This encompasses the vast majority
31661 of legitimate HELO domains.
31663 The &'dnsdb'& lookup also has support for CSA. Although &'dnsdb'& also supports
31664 direct SRV lookups, this is not sufficient because of the extra parent domain
31665 search behaviour of CSA, and (as with PTR lookups) &'dnsdb'& also turns IP
31666 addresses into lookups in the reverse DNS space. The result of a successful
31669 ${lookup dnsdb {csa=$sender_helo_name}}
31671 has two space-separated fields: an authorization code and a target host name.
31672 The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit
31673 authorization required but absent, or &"?"& for unknown.
31678 .section "Bounce address tag validation" "SECTverifyPRVS"
31679 .cindex "BATV, verifying"
31680 Bounce address tag validation (BATV) is a scheme whereby the envelope senders
31681 of outgoing messages have a cryptographic, timestamped &"tag"& added to them.
31682 Genuine incoming bounce messages should therefore always be addressed to
31683 recipients that have a valid tag. This scheme is a way of detecting unwanted
31684 bounce messages caused by sender address forgeries (often called &"collateral
31685 spam"&), because the recipients of such messages do not include valid tags.
31687 There are two expansion items to help with the implementation of the BATV
31688 &"prvs"& (private signature) scheme in an Exim configuration. This scheme signs
31689 the original envelope sender address by using a simple key to add a hash of the
31690 address and some time-based randomizing information. The &%prvs%& expansion
31691 item creates a signed address, and the &%prvscheck%& expansion item checks one.
31692 The syntax of these expansion items is described in section
31693 &<<SECTexpansionitems>>&.
31694 The validity period on signed addresses is seven days.
31696 As an example, suppose the secret per-address keys are stored in an MySQL
31697 database. A query to look up the key for an address could be defined as a macro
31700 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs \
31701 WHERE sender='${quote_mysql:$prvscheck_address}'\
31704 Suppose also that the senders who make use of BATV are defined by an address
31705 list called &%batv_senders%&. Then, in the ACL for RCPT commands, you could
31708 # Bounces: drop unsigned addresses for BATV senders
31709 deny message = This address does not send an unsigned reverse path
31711 recipients = +batv_senders
31713 # Bounces: In case of prvs-signed address, check signature.
31714 deny message = Invalid reverse path signature.
31716 condition = ${prvscheck {$local_part@$domain}\
31717 {PRVSCHECK_SQL}{1}}
31718 !condition = $prvscheck_result
31720 The first statement rejects recipients for bounce messages that are addressed
31721 to plain BATV sender addresses, because it is known that BATV senders do not
31722 send out messages with plain sender addresses. The second statement rejects
31723 recipients that are prvs-signed, but with invalid signatures (either because
31724 the key is wrong, or the signature has timed out).
31726 A non-prvs-signed address is not rejected by the second statement, because the
31727 &%prvscheck%& expansion yields an empty string if its first argument is not a
31728 prvs-signed address, thus causing the &%condition%& condition to be false. If
31729 the first argument is a syntactically valid prvs-signed address, the yield is
31730 the third string (in this case &"1"&), whether or not the cryptographic and
31731 timeout checks succeed. The &$prvscheck_result$& variable contains the result
31732 of the checks (empty for failure, &"1"& for success).
31734 There is one more issue you must consider when implementing prvs-signing:
31735 you have to ensure that the routers accept prvs-signed addresses and
31736 deliver them correctly. The easiest way to handle this is to use a &(redirect)&
31737 router to remove the signature with a configuration along these lines:
31741 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}}
31743 This works because, if the third argument of &%prvscheck%& is empty, the result
31744 of the expansion of a prvs-signed address is the decoded value of the original
31745 address. This router should probably be the first of your routers that handles
31748 To create BATV-signed addresses in the first place, a transport of this form
31751 external_smtp_batv:
31753 return_path = ${prvs {$return_path} \
31754 {${lookup mysql{SELECT \
31755 secret FROM batv_prvs WHERE \
31756 sender='${quote_mysql:$sender_address}'} \
31759 If no key can be found for the existing return path, no signing takes place.
31763 .section "Using an ACL to control relaying" "SECTrelaycontrol"
31764 .cindex "&ACL;" "relay control"
31765 .cindex "relaying" "control by ACL"
31766 .cindex "policy control" "relay control"
31767 An MTA is said to &'relay'& a message if it receives it from some host and
31768 delivers it directly to another host as a result of a remote address contained
31769 within it. Redirecting a local address via an alias or forward file and then
31770 passing the message on to another host is not relaying,
31771 .cindex "&""percent hack""&"
31772 but a redirection as a result of the &"percent hack"& is.
31774 Two kinds of relaying exist, which are termed &"incoming"& and &"outgoing"&.
31775 A host which is acting as a gateway or an MX backup is concerned with incoming
31776 relaying from arbitrary hosts to a specific set of domains. On the other hand,
31777 a host which is acting as a smart host for a number of clients is concerned
31778 with outgoing relaying from those clients to the Internet at large. Often the
31779 same host is fulfilling both functions,
31781 . as illustrated in the diagram below,
31783 but in principle these two kinds of relaying are entirely independent. What is
31784 not wanted is the transmission of mail from arbitrary remote hosts through your
31785 system to arbitrary domains.
31788 You can implement relay control by means of suitable statements in the ACL that
31789 runs for each RCPT command. For convenience, it is often easiest to use
31790 Exim's named list facility to define the domains and hosts involved. For
31791 example, suppose you want to do the following:
31794 Deliver a number of domains to mailboxes on the local host (or process them
31795 locally in some other way). Let's say these are &'my.dom1.example'& and
31796 &'my.dom2.example'&.
31798 Relay mail for a number of other domains for which you are the secondary MX.
31799 These might be &'friend1.example'& and &'friend2.example'&.
31801 Relay mail from the hosts on your local LAN, to whatever domains are involved.
31802 Suppose your LAN is 192.168.45.0/24.
31806 In the main part of the configuration, you put the following definitions:
31808 domainlist local_domains = my.dom1.example : my.dom2.example
31809 domainlist relay_to_domains = friend1.example : friend2.example
31810 hostlist relay_from_hosts = 192.168.45.0/24
31812 Now you can use these definitions in the ACL that is run for every RCPT
31816 accept domains = +local_domains : +relay_to_domains
31817 accept hosts = +relay_from_hosts
31819 The first statement accepts any RCPT command that contains an address in
31820 the local or relay domains. For any other domain, control passes to the second
31821 statement, which accepts the command only if it comes from one of the relay
31822 hosts. In practice, you will probably want to make your ACL more sophisticated
31823 than this, for example, by including sender and recipient verification. The
31824 default configuration includes a more comprehensive example, which is described
31825 in chapter &<<CHAPdefconfil>>&.
31829 .section "Checking a relay configuration" "SECTcheralcon"
31830 .cindex "relaying" "checking control of"
31831 You can check the relay characteristics of your configuration in the same way
31832 that you can test any ACL behaviour for an incoming SMTP connection, by using
31833 the &%-bh%& option to run a fake SMTP session with which you interact.
31838 . ////////////////////////////////////////////////////////////////////////////
31839 . ////////////////////////////////////////////////////////////////////////////
31841 .chapter "Content scanning at ACL time" "CHAPexiscan"
31842 .scindex IIDcosca "content scanning" "at ACL time"
31843 The extension of Exim to include content scanning at ACL time, formerly known
31844 as &"exiscan"&, was originally implemented as a patch by Tom Kistner. The code
31845 was integrated into the main source for Exim release 4.50, and Tom continues to
31846 maintain it. Most of the wording of this chapter is taken from Tom's
31849 It is also possible to scan the content of messages at other times. The
31850 &[local_scan()]& function (see chapter &<<CHAPlocalscan>>&) allows for content
31851 scanning after all the ACLs have run. A transport filter can be used to scan
31852 messages at delivery time (see the &%transport_filter%& option, described in
31853 chapter &<<CHAPtransportgeneric>>&).
31855 If you want to include the ACL-time content-scanning features when you compile
31856 Exim, you need to arrange for WITH_CONTENT_SCAN to be defined in your
31857 &_Local/Makefile_&. When you do that, the Exim binary is built with:
31860 Two additional ACLs (&%acl_smtp_mime%& and &%acl_not_smtp_mime%&) that are run
31861 for all MIME parts for SMTP and non-SMTP messages, respectively.
31863 Additional ACL conditions and modifiers: &%decode%&, &%malware%&,
31864 &%mime_regex%&, &%regex%&, and &%spam%&. These can be used in the ACL that is
31865 run at the end of message reception (the &%acl_smtp_data%& ACL).
31867 An additional control feature (&"no_mbox_unspool"&) that saves spooled copies
31868 of messages, or parts of messages, for debugging purposes.
31870 Additional expansion variables that are set in the new ACL and by the new
31873 Two new main configuration options: &%av_scanner%& and &%spamd_address%&.
31876 Content-scanning is continually evolving, and new features are still being
31877 added. While such features are still unstable and liable to incompatible
31878 changes, they are made available in Exim by setting options whose names begin
31879 EXPERIMENTAL_ in &_Local/Makefile_&. Such features are not documented in
31880 this manual. You can find out about them by reading the file called
31881 &_doc/experimental.txt_&.
31883 All the content-scanning facilities work on a MBOX copy of the message that is
31884 temporarily created in a file called:
31886 <&'spool_directory'&>&`/scan/`&<&'message_id'&>/<&'message_id'&>&`.eml`&
31888 The &_.eml_& extension is a friendly hint to virus scanners that they can
31889 expect an MBOX-like structure inside that file. The file is created when the
31890 first content scanning facility is called. Subsequent calls to content
31891 scanning conditions open the same file again. The directory is recursively
31892 removed when the &%acl_smtp_data%& ACL has finished running, unless
31894 control = no_mbox_unspool
31896 has been encountered. When the MIME ACL decodes files, they are put into the
31897 same directory by default.
31901 .section "Scanning for viruses" "SECTscanvirus"
31902 .cindex "virus scanning"
31903 .cindex "content scanning" "for viruses"
31904 .cindex "content scanning" "the &%malware%& condition"
31905 The &%malware%& ACL condition lets you connect virus scanner software to Exim.
31906 It supports a &"generic"& interface to scanners called via the shell, and
31907 specialized interfaces for &"daemon"& type virus scanners, which are resident
31908 in memory and thus are much faster.
31910 A timeout of 2 minutes is applied to a scanner call (by default);
31911 if it expires then a defer action is taken.
31913 .oindex "&%av_scanner%&"
31914 You can set the &%av_scanner%& option in the main part of the configuration
31915 to specify which scanner to use, together with any additional options that
31916 are needed. The basic syntax is as follows:
31918 &`av_scanner = <`&&'scanner-type'&&`>:<`&&'option1'&&`>:<`&&'option2'&&`>:[...]`&
31920 If you do not set &%av_scanner%&, it defaults to
31922 av_scanner = sophie:/var/run/sophie
31924 If the value of &%av_scanner%& starts with a dollar character, it is expanded
31926 The usual list-parsing of the content (see &<<SECTlistconstruct>>&) applies.
31927 The following scanner types are supported in this release,
31928 though individual ones can be included or not at build time:
31932 .cindex "virus scanners" "avast"
31933 This is the scanner daemon of Avast. It has been tested with Avast Core
31934 Security (currently at version 2.2.0).
31935 You can get a trial version at &url(https://www.avast.com) or for Linux
31936 at &url(https://www.avast.com/linux-server-antivirus).
31937 This scanner type takes one option,
31938 which can be either a full path to a UNIX socket,
31939 or host and port specifiers separated by white space.
31940 The host may be a name or an IP address; the port is either a
31941 single number or a pair of numbers with a dash between.
31942 A list of options may follow. These options are interpreted on the
31943 Exim's side of the malware scanner, or are given on separate lines to
31944 the daemon as options before the main scan command.
31946 .cindex &`pass_unscanned`& "avast"
31947 If &`pass_unscanned`&
31948 is set, any files the Avast scanner can't scan (e.g.
31949 decompression bombs, or invalid archives) are considered clean. Use with
31954 av_scanner = avast:/var/run/avast/scan.sock:FLAGS -fullfiles:SENSITIVITY -pup
31955 av_scanner = avast:/var/run/avast/scan.sock:pass_unscanned:FLAGS -fullfiles:SENSITIVITY -pup
31956 av_scanner = avast:192.168.2.22 5036
31958 If you omit the argument, the default path
31959 &_/var/run/avast/scan.sock_&
31961 If you use a remote host,
31962 you need to make Exim's spool directory available to it,
31963 as the scanner is passed a file path, not file contents.
31964 For information about available commands and their options you may use
31966 $ socat UNIX:/var/run/avast/scan.sock STDIO:
31972 If the scanner returns a temporary failure (e.g. license issues, or
31973 permission problems), the message is deferred and a paniclog entry is
31974 written. The usual &`defer_ok`& option is available.
31976 .vitem &%aveserver%&
31977 .cindex "virus scanners" "Kaspersky"
31978 This is the scanner daemon of Kaspersky Version 5. You can get a trial version
31979 at &url(http://www.kaspersky.com). This scanner type takes one option,
31980 which is the path to the daemon's UNIX socket. The default is shown in this
31983 av_scanner = aveserver:/var/run/aveserver
31988 .cindex "virus scanners" "clamd"
31989 This daemon-type scanner is GPL and free. You can get it at
31990 &url(http://www.clamav.net/). Some older versions of clamd do not seem to
31991 unpack MIME containers, so it used to be recommended to unpack MIME attachments
31992 in the MIME ACL. This is no longer believed to be necessary.
31994 The options are a list of server specifiers, which may be
31995 a UNIX socket specification,
31996 a TCP socket specification,
31997 or a (global) option.
31999 A socket specification consists of a space-separated list.
32000 For a Unix socket the first element is a full path for the socket,
32001 for a TCP socket the first element is the IP address
32002 and the second a port number,
32003 Any further elements are per-server (non-global) options.
32004 These per-server options are supported:
32006 retry=<timespec> Retry on connect fail
32009 The &`retry`& option specifies a time after which a single retry for
32010 a failed connect is made. The default is to not retry.
32012 If a Unix socket file is specified, only one server is supported.
32016 av_scanner = clamd:/opt/clamd/socket
32017 av_scanner = clamd:192.0.2.3 1234
32018 av_scanner = clamd:192.0.2.3 1234:local
32019 av_scanner = clamd:192.0.2.3 1234 retry=10s
32020 av_scanner = clamd:192.0.2.3 1234 : 192.0.2.4 1234
32022 If the value of av_scanner points to a UNIX socket file or contains the
32024 option, then the ClamAV interface will pass a filename containing the data
32025 to be scanned, which should normally result in less I/O happening and be
32026 more efficient. Normally in the TCP case, the data is streamed to ClamAV as
32027 Exim does not assume that there is a common filesystem with the remote host.
32029 The final example shows that multiple TCP targets can be specified. Exim will
32030 randomly use one for each incoming email (i.e. it load balances them). Note
32031 that only TCP targets may be used if specifying a list of scanners; a UNIX
32032 socket cannot be mixed in with TCP targets. If one of the servers becomes
32033 unavailable, Exim will try the remaining one(s) until it finds one that works.
32034 When a clamd server becomes unreachable, Exim will log a message. Exim does
32035 not keep track of scanner state between multiple messages, and the scanner
32036 selection is random, so the message will get logged in the mainlog for each
32037 email that the down scanner gets chosen first (message wrapped to be readable):
32039 2013-10-09 14:30:39 1VTumd-0000Y8-BQ malware acl condition:
32040 clamd: connection to localhost, port 3310 failed
32041 (Connection refused)
32044 If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for
32045 contributing the code for this scanner.
32048 .cindex "virus scanners" "command line interface"
32049 This is the keyword for the generic command line scanner interface. It can be
32050 used to attach virus scanners that are invoked from the shell. This scanner
32051 type takes 3 mandatory options:
32054 The full path and name of the scanner binary, with all command line options,
32055 and a placeholder (&`%s`&) for the directory to scan.
32058 A regular expression to match against the STDOUT and STDERR output of the
32059 virus scanner. If the expression matches, a virus was found. You must make
32060 absolutely sure that this expression matches on &"virus found"&. This is called
32061 the &"trigger"& expression.
32064 Another regular expression, containing exactly one pair of parentheses, to
32065 match the name of the virus found in the scanners output. This is called the
32066 &"name"& expression.
32069 For example, Sophos Sweep reports a virus on a line like this:
32071 Virus 'W32/Magistr-B' found in file ./those.bat
32073 For the trigger expression, we can match the phrase &"found in file"&. For the
32074 name expression, we want to extract the W32/Magistr-B string, so we can match
32075 for the single quotes left and right of it. Altogether, this makes the
32076 configuration setting:
32078 av_scanner = cmdline:\
32079 /path/to/sweep -ss -all -rec -archive %s:\
32080 found in file:'(.+)'
32083 .cindex "virus scanners" "DrWeb"
32084 The DrWeb daemon scanner (&url(http://www.sald.com/)) interface
32086 either a full path to a UNIX socket,
32087 or host and port specifiers separated by white space.
32088 The host may be a name or an IP address; the port is either a
32089 single number or a pair of numbers with a dash between.
32092 av_scanner = drweb:/var/run/drwebd.sock
32093 av_scanner = drweb:192.168.2.20 31337
32095 If you omit the argument, the default path &_/usr/local/drweb/run/drwebd.sock_&
32096 is used. Thanks to Alex Miller for contributing the code for this scanner.
32099 .cindex "virus scanners" "f-protd"
32100 The f-protd scanner is accessed via HTTP over TCP.
32101 One argument is taken, being a space-separated hostname and port number
32105 av_scanner = f-protd:localhost 10200-10204
32107 If you omit the argument, the default values shown above are used.
32109 .vitem &%f-prot6d%&
32110 .cindex "virus scanners" "f-prot6d"
32111 The f-prot6d scanner is accessed using the FPSCAND protocol over TCP.
32112 One argument is taken, being a space-separated hostname and port number.
32115 av_scanner = f-prot6d:localhost 10200
32117 If you omit the argument, the default values show above are used.
32120 .cindex "virus scanners" "F-Secure"
32121 The F-Secure daemon scanner (&url(http://www.f-secure.com)) takes one
32122 argument which is the path to a UNIX socket. For example:
32124 av_scanner = fsecure:/path/to/.fsav
32126 If no argument is given, the default is &_/var/run/.fsav_&. Thanks to Johan
32127 Thelmen for contributing the code for this scanner.
32129 .vitem &%kavdaemon%&
32130 .cindex "virus scanners" "Kaspersky"
32131 This is the scanner daemon of Kaspersky Version 4. This version of the
32132 Kaspersky scanner is outdated. Please upgrade (see &%aveserver%& above). This
32133 scanner type takes one option, which is the path to the daemon's UNIX socket.
32136 av_scanner = kavdaemon:/opt/AVP/AvpCtl
32138 The default path is &_/var/run/AvpCtl_&.
32141 .cindex "virus scanners" "mksd"
32142 This is a daemon type scanner that is aimed mainly at Polish users, though some
32143 parts of documentation are now available in English. You can get it at
32144 &url(http://linux.mks.com.pl/). The only option for this scanner type is
32145 the maximum number of processes used simultaneously to scan the attachments,
32146 provided that mksd has
32147 been run with at least the same number of child processes. For example:
32149 av_scanner = mksd:2
32151 You can safely omit this option (the default value is 1).
32154 .cindex "virus scanners" "simple socket-connected"
32155 This is a general-purpose way of talking to simple scanner daemons
32156 running on the local machine.
32157 There are four options:
32158 an address (which may be an IP address and port, or the path of a Unix socket),
32159 a commandline to send (may include a single %s which will be replaced with
32160 the path to the mail file to be scanned),
32161 an RE to trigger on from the returned data,
32162 and an RE to extract malware_name from the returned data.
32165 av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
32167 Note that surrounding whitespace is stripped from each option, meaning
32168 there is no way to specify a trailing newline.
32169 The socket specifier and both regular-expressions are required.
32170 Default for the commandline is &_%s\n_& (note this does have a trailing newline);
32171 specify an empty element to get this.
32174 .cindex "virus scanners" "Sophos and Sophie"
32175 Sophie is a daemon that uses Sophos' &%libsavi%& library to scan for viruses.
32176 You can get Sophie at &url(http://www.clanfield.info/sophie/). The only option
32177 for this scanner type is the path to the UNIX socket that Sophie uses for
32178 client communication. For example:
32180 av_scanner = sophie:/tmp/sophie
32182 The default path is &_/var/run/sophie_&, so if you are using this, you can omit
32186 When &%av_scanner%& is correctly set, you can use the &%malware%& condition in
32187 the DATA ACL. &*Note*&: You cannot use the &%malware%& condition in the MIME
32190 The &%av_scanner%& option is expanded each time &%malware%& is called. This
32191 makes it possible to use different scanners. See further below for an example.
32192 The &%malware%& condition caches its results, so when you use it multiple times
32193 for the same message, the actual scanning process is only carried out once.
32194 However, using expandable items in &%av_scanner%& disables this caching, in
32195 which case each use of the &%malware%& condition causes a new scan of the
32198 The &%malware%& condition takes a right-hand argument that is expanded before
32199 use and taken as a list, slash-separated by default.
32200 The first element can then be one of
32203 &"true"&, &"*"&, or &"1"&, in which case the message is scanned for viruses.
32204 The condition succeeds if a virus was found, and fail otherwise. This is the
32207 &"false"& or &"0"& or an empty string, in which case no scanning is done and
32208 the condition fails immediately.
32210 A regular expression, in which case the message is scanned for viruses. The
32211 condition succeeds if a virus is found and its name matches the regular
32212 expression. This allows you to take special actions on certain types of virus.
32213 Note that &"/"& characters in the RE must be doubled due to the list-processing,
32214 unless the separator is changed (in the usual way).
32217 You can append a &`defer_ok`& element to the &%malware%& argument list to accept
32218 messages even if there is a problem with the virus scanner.
32219 Otherwise, such a problem causes the ACL to defer.
32221 You can append a &`tmo=<val>`& element to the &%malware%& argument list to
32222 specify a non-default timeout. The default is two minutes.
32225 malware = * / defer_ok / tmo=10s
32227 A timeout causes the ACL to defer.
32229 .vindex "&$callout_address$&"
32230 When a connection is made to the scanner the expansion variable &$callout_address$&
32231 is set to record the actual address used.
32233 .vindex "&$malware_name$&"
32234 When a virus is found, the condition sets up an expansion variable called
32235 &$malware_name$& that contains the name of the virus. You can use it in a
32236 &%message%& modifier that specifies the error returned to the sender, and/or in
32239 Beware the interaction of Exim's &%message_size_limit%& with any size limits
32240 imposed by your anti-virus scanner.
32242 Here is a very simple scanning example:
32244 deny message = This message contains malware ($malware_name)
32247 The next example accepts messages when there is a problem with the scanner:
32249 deny message = This message contains malware ($malware_name)
32250 malware = */defer_ok
32252 The next example shows how to use an ACL variable to scan with both sophie and
32253 aveserver. It assumes you have set:
32255 av_scanner = $acl_m0
32257 in the main Exim configuration.
32259 deny message = This message contains malware ($malware_name)
32260 set acl_m0 = sophie
32263 deny message = This message contains malware ($malware_name)
32264 set acl_m0 = aveserver
32269 .section "Scanning with SpamAssassin" "SECTscanspamass"
32270 .cindex "content scanning" "for spam"
32271 .cindex "spam scanning"
32272 .cindex "SpamAssassin"
32273 The &%spam%& ACL condition calls SpamAssassin's &%spamd%& daemon to get a spam
32274 score and a report for the message. You can get SpamAssassin at
32275 &url(http://www.spamassassin.org), or, if you have a working Perl
32276 installation, you can use CPAN by running:
32278 perl -MCPAN -e 'install Mail::SpamAssassin'
32280 SpamAssassin has its own set of configuration files. Please review its
32281 documentation to see how you can tweak it. The default installation should work
32284 .oindex "&%spamd_address%&"
32285 By default, SpamAssassin listens on 127.0.0.1, TCP port 783 and if you
32286 intend to use an instance running on the local host you do not need to set
32287 &%spamd_address%&. If you intend to use another host or port for SpamAssassin,
32288 you must set the &%spamd_address%& option in the global part of the Exim
32289 configuration as follows (example):
32291 spamd_address = 192.168.99.45 387
32293 The SpamAssassin protocol relies on a TCP half-close from the client.
32294 If your SpamAssassin client side is running a Linux system with an
32295 iptables firewall, consider setting
32296 &%net.netfilter.nf_conntrack_tcp_timeout_close_wait%& to at least the
32297 timeout, Exim uses when waiting for a response from the SpamAssassin
32298 server (currently defaulting to 120s). With a lower value the Linux
32299 connection tracking may consider your half-closed connection as dead too
32302 As of version 2.60, &%SpamAssassin%& also supports communication over UNIX
32303 sockets. If you want to us these, supply &%spamd_address%& with an absolute
32304 file name instead of an address/port pair:
32306 spamd_address = /var/run/spamd_socket
32308 You can have multiple &%spamd%& servers to improve scalability. These can
32309 reside on other hardware reachable over the network. To specify multiple
32310 &%spamd%& servers, put multiple address/port pairs in the &%spamd_address%&
32311 option, separated with colons (the separator can be changed in the usual way):
32313 spamd_address = 192.168.2.10 783 : \
32314 192.168.2.11 783 : \
32317 Up to 32 &%spamd%& servers are supported.
32318 When a server fails to respond to the connection attempt, all other
32319 servers are tried until one succeeds. If no server responds, the &%spam%&
32322 Unix and TCP socket specifications may be mixed in any order.
32323 Each element of the list is a list itself, space-separated by default
32324 and changeable in the usual way; take care to not double the separator.
32326 For TCP socket specifications a host name or IP (v4 or v6, but
32327 subject to list-separator quoting rules) address can be used,
32328 and the port can be one or a dash-separated pair.
32329 In the latter case, the range is tried in strict order.
32331 Elements after the first for Unix sockets, or second for TCP socket,
32333 The supported options are:
32335 pri=<priority> Selection priority
32336 weight=<value> Selection bias
32337 time=<start>-<end> Use only between these times of day
32338 retry=<timespec> Retry on connect fail
32339 tmo=<timespec> Connection time limit
32340 variant=rspamd Use Rspamd rather than SpamAssassin protocol
32343 The &`pri`& option specifies a priority for the server within the list,
32344 higher values being tried first.
32345 The default priority is 1.
32347 The &`weight`& option specifies a selection bias.
32348 Within a priority set
32349 servers are queried in a random fashion, weighted by this value.
32350 The default value for selection bias is 1.
32352 Time specifications for the &`time`& option are <hour>.<minute>.<second>
32353 in the local time zone; each element being one or more digits.
32354 Either the seconds or both minutes and seconds, plus the leading &`.`&
32355 characters, may be omitted and will be taken as zero.
32357 Timeout specifications for the &`retry`& and &`tmo`& options
32358 are the usual Exim time interval standard, e.g. &`20s`& or &`1m`&.
32360 The &`tmo`& option specifies an overall timeout for communication.
32361 The default value is two minutes.
32363 The &`retry`& option specifies a time after which a single retry for
32364 a failed connect is made.
32365 The default is to not retry.
32367 The &%spamd_address%& variable is expanded before use if it starts with
32368 a dollar sign. In this case, the expansion may return a string that is
32369 used as the list so that multiple spamd servers can be the result of an
32372 .vindex "&$callout_address$&"
32373 When a connection is made to the server the expansion variable &$callout_address$&
32374 is set to record the actual address used.
32376 .section "Calling SpamAssassin from an Exim ACL" "SECID206"
32377 Here is a simple example of the use of the &%spam%& condition in a DATA ACL:
32379 deny message = This message was classified as SPAM
32382 The right-hand side of the &%spam%& condition specifies a name. This is
32383 relevant if you have set up multiple SpamAssassin profiles. If you do not want
32384 to scan using a specific profile, but rather use the SpamAssassin system-wide
32385 default profile, you can scan for an unknown name, or simply use &"nobody"&.
32386 However, you must put something on the right-hand side.
32388 The name allows you to use per-domain or per-user antispam profiles in
32389 principle, but this is not straightforward in practice, because a message may
32390 have multiple recipients, not necessarily all in the same domain. Because the
32391 &%spam%& condition has to be called from a DATA-time ACL in order to be able to
32392 read the contents of the message, the variables &$local_part$& and &$domain$&
32394 Careful enforcement of single-recipient messages
32395 (e.g. by responding with defer in the recipient ACL for all recipients
32397 or the use of PRDR,
32398 .cindex "PRDR" "use for per-user SpamAssassin profiles"
32399 are needed to use this feature.
32401 The right-hand side of the &%spam%& condition is expanded before being used, so
32402 you can put lookups or conditions there. When the right-hand side evaluates to
32403 &"0"& or &"false"&, no scanning is done and the condition fails immediately.
32406 Scanning with SpamAssassin uses a lot of resources. If you scan every message,
32407 large ones may cause significant performance degradation. As most spam messages
32408 are quite small, it is recommended that you do not scan the big ones. For
32411 deny message = This message was classified as SPAM
32412 condition = ${if < {$message_size}{10K}}
32416 The &%spam%& condition returns true if the threshold specified in the user's
32417 SpamAssassin profile has been matched or exceeded. If you want to use the
32418 &%spam%& condition for its side effects (see the variables below), you can make
32419 it always return &"true"& by appending &`:true`& to the username.
32421 .cindex "spam scanning" "returned variables"
32422 When the &%spam%& condition is run, it sets up a number of expansion
32424 Except for &$spam_report$&,
32425 these variables are saved with the received message so are
32426 available for use at delivery time.
32429 .vitem &$spam_score$&
32430 The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful
32431 for inclusion in log or reject messages.
32433 .vitem &$spam_score_int$&
32434 The spam score of the message, multiplied by ten, as an integer value. For
32435 example &"34"& or &"305"&. It may appear to disagree with &$spam_score$&
32436 because &$spam_score$& is rounded and &$spam_score_int$& is truncated.
32437 The integer value is useful for numeric comparisons in conditions.
32439 .vitem &$spam_bar$&
32440 A string consisting of a number of &"+"& or &"-"& characters, representing the
32441 integer part of the spam score value. A spam score of 4.4 would have a
32442 &$spam_bar$& value of &"++++"&. This is useful for inclusion in warning
32443 headers, since MUAs can match on such strings. The maximum length of the
32444 spam bar is 50 characters.
32446 .vitem &$spam_report$&
32447 A multiline text table, containing the full SpamAssassin report for the
32448 message. Useful for inclusion in headers or reject messages.
32449 This variable is only usable in a DATA-time ACL.
32450 Beware that SpamAssassin may return non-ASCII characters, especially
32451 when running in country-specific locales, which are not legal
32452 unencoded in headers.
32454 .vitem &$spam_action$&
32455 Either 'reject' or 'no action' depending on the
32456 spam score versus threshold.
32459 The &%spam%& condition caches its results unless expansion in
32460 spamd_address was used. If you call it again with the same user name, it
32461 does not scan again, but rather returns the same values as before.
32463 The &%spam%& condition returns DEFER if there is any error while running
32464 the message through SpamAssassin or if the expansion of spamd_address
32465 failed. If you want to treat DEFER as FAIL (to pass on to the next ACL
32466 statement block), append &`/defer_ok`& to the right-hand side of the
32467 spam condition, like this:
32469 deny message = This message was classified as SPAM
32470 spam = joe/defer_ok
32472 This causes messages to be accepted even if there is a problem with &%spamd%&.
32474 Here is a longer, commented example of the use of the &%spam%&
32477 # put headers in all messages (no matter if spam or not)
32478 warn spam = nobody:true
32479 add_header = X-Spam-Score: $spam_score ($spam_bar)
32480 add_header = X-Spam-Report: $spam_report
32482 # add second subject line with *SPAM* marker when message
32483 # is over threshold
32485 add_header = Subject: *SPAM* $h_Subject:
32487 # reject spam at high scores (> 12)
32488 deny message = This message scored $spam_score spam points.
32490 condition = ${if >{$spam_score_int}{120}{1}{0}}
32495 .section "Scanning MIME parts" "SECTscanmimepart"
32496 .cindex "content scanning" "MIME parts"
32497 .cindex "MIME content scanning"
32498 .oindex "&%acl_smtp_mime%&"
32499 .oindex "&%acl_not_smtp_mime%&"
32500 The &%acl_smtp_mime%& global option specifies an ACL that is called once for
32501 each MIME part of an SMTP message, including multipart types, in the sequence
32502 of their position in the message. Similarly, the &%acl_not_smtp_mime%& option
32503 specifies an ACL that is used for the MIME parts of non-SMTP messages. These
32504 options may both refer to the same ACL if you want the same processing in both
32507 These ACLs are called (possibly many times) just before the &%acl_smtp_data%&
32508 ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in
32509 the case of a non-SMTP message. However, a MIME ACL is called only if the
32510 message contains a &'Content-Type:'& header line. When a call to a MIME
32511 ACL does not yield &"accept"&, ACL processing is aborted and the appropriate
32512 result code is sent to the client. In the case of an SMTP message, the
32513 &%acl_smtp_data%& ACL is not called when this happens.
32515 You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can
32516 only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%&
32517 condition to match against the raw MIME part. You can also use the
32518 &%mime_regex%& condition to match against the decoded MIME part (see section
32519 &<<SECTscanregex>>&).
32521 At the start of a MIME ACL, a number of variables are set from the header
32522 information for the relevant MIME part. These are described below. The contents
32523 of the MIME part are not by default decoded into a disk file except for MIME
32524 parts whose content-type is &"message/rfc822"&. If you want to decode a MIME
32525 part into a disk file, you can use the &%decode%& condition. The general
32528 &`decode = [/`&<&'path'&>&`/]`&<&'filename'&>
32530 The right hand side is expanded before use. After expansion,
32534 &"0"& or &"false"&, in which case no decoding is done.
32536 The string &"default"&. In that case, the file is put in the temporary
32537 &"default"& directory <&'spool_directory'&>&_/scan/_&<&'message_id'&>&_/_& with
32538 a sequential file name consisting of the message id and a sequence number. The
32539 full path and name is available in &$mime_decoded_filename$& after decoding.
32541 A full path name starting with a slash. If the full name is an existing
32542 directory, it is used as a replacement for the default directory. The filename
32543 is then sequentially assigned. If the path does not exist, it is used as
32544 the full path and file name.
32546 If the string does not start with a slash, it is used as the
32547 filename, and the default path is then used.
32549 The &%decode%& condition normally succeeds. It is only false for syntax
32550 errors or unusual circumstances such as memory shortages. You can easily decode
32551 a file with its original, proposed filename using
32553 decode = $mime_filename
32555 However, you should keep in mind that &$mime_filename$& might contain
32556 anything. If you place files outside of the default path, they are not
32557 automatically unlinked.
32559 For RFC822 attachments (these are messages attached to messages, with a
32560 content-type of &"message/rfc822"&), the ACL is called again in the same manner
32561 as for the primary message, only that the &$mime_is_rfc822$& expansion
32562 variable is set (see below). Attached messages are always decoded to disk
32563 before being checked, and the files are unlinked once the check is done.
32565 The MIME ACL supports the &%regex%& and &%mime_regex%& conditions. These can be
32566 used to match regular expressions against raw and decoded MIME parts,
32567 respectively. They are described in section &<<SECTscanregex>>&.
32569 .cindex "MIME content scanning" "returned variables"
32570 The following list describes all expansion variables that are
32571 available in the MIME ACL:
32574 .vitem &$mime_boundary$&
32575 If the current part is a multipart (see &$mime_is_multipart$&) below, it should
32576 have a boundary string, which is stored in this variable. If the current part
32577 has no boundary parameter in the &'Content-Type:'& header, this variable
32578 contains the empty string.
32580 .vitem &$mime_charset$&
32581 This variable contains the character set identifier, if one was found in the
32582 &'Content-Type:'& header. Examples for charset identifiers are:
32588 Please note that this value is not normalized, so you should do matches
32589 case-insensitively.
32591 .vitem &$mime_content_description$&
32592 This variable contains the normalized content of the &'Content-Description:'&
32593 header. It can contain a human-readable description of the parts content. Some
32594 implementations repeat the filename for attachments here, but they are usually
32595 only used for display purposes.
32597 .vitem &$mime_content_disposition$&
32598 This variable contains the normalized content of the &'Content-Disposition:'&
32599 header. You can expect strings like &"attachment"& or &"inline"& here.
32601 .vitem &$mime_content_id$&
32602 This variable contains the normalized content of the &'Content-ID:'& header.
32603 This is a unique ID that can be used to reference a part from another part.
32605 .vitem &$mime_content_size$&
32606 This variable is set only after the &%decode%& modifier (see above) has been
32607 successfully run. It contains the size of the decoded part in kilobytes. The
32608 size is always rounded up to full kilobytes, so only a completely empty part
32609 has a &$mime_content_size$& of zero.
32611 .vitem &$mime_content_transfer_encoding$&
32612 This variable contains the normalized content of the
32613 &'Content-transfer-encoding:'& header. This is a symbolic name for an encoding
32614 type. Typical values are &"base64"& and &"quoted-printable"&.
32616 .vitem &$mime_content_type$&
32617 If the MIME part has a &'Content-Type:'& header, this variable contains its
32618 value, lowercased, and without any options (like &"name"& or &"charset"&). Here
32619 are some examples of popular MIME types, as they may appear in this variable:
32623 application/octet-stream
32627 If the MIME part has no &'Content-Type:'& header, this variable contains the
32630 .vitem &$mime_decoded_filename$&
32631 This variable is set only after the &%decode%& modifier (see above) has been
32632 successfully run. It contains the full path and file name of the file
32633 containing the decoded data.
32638 .vitem &$mime_filename$&
32639 This is perhaps the most important of the MIME variables. It contains a
32640 proposed filename for an attachment, if one was found in either the
32641 &'Content-Type:'& or &'Content-Disposition:'& headers. The filename will be
32644 decoded, but no additional sanity checks are done.
32646 found, this variable contains the empty string.
32648 .vitem &$mime_is_coverletter$&
32649 This variable attempts to differentiate the &"cover letter"& of an e-mail from
32650 attached data. It can be used to clamp down on flashy or unnecessarily encoded
32651 content in the cover letter, while not restricting attachments at all.
32653 The variable contains 1 (true) for a MIME part believed to be part of the
32654 cover letter, and 0 (false) for an attachment. At present, the algorithm is as
32658 The outermost MIME part of a message is always a cover letter.
32661 If a multipart/alternative or multipart/related MIME part is a cover letter,
32662 so are all MIME subparts within that multipart.
32665 If any other multipart is a cover letter, the first subpart is a cover letter,
32666 and the rest are attachments.
32669 All parts contained within an attachment multipart are attachments.
32672 As an example, the following will ban &"HTML mail"& (including that sent with
32673 alternative plain text), while allowing HTML files to be attached. HTML
32674 coverletter mail attached to non-HTML coverletter mail will also be allowed:
32676 deny message = HTML mail is not accepted here
32677 !condition = $mime_is_rfc822
32678 condition = $mime_is_coverletter
32679 condition = ${if eq{$mime_content_type}{text/html}{1}{0}}
32681 .vitem &$mime_is_multipart$&
32682 This variable has the value 1 (true) when the current part has the main type
32683 &"multipart"&, for example &"multipart/alternative"& or &"multipart/mixed"&.
32684 Since multipart entities only serve as containers for other parts, you may not
32685 want to carry out specific actions on them.
32687 .vitem &$mime_is_rfc822$&
32688 This variable has the value 1 (true) if the current part is not a part of the
32689 checked message itself, but part of an attached message. Attached message
32690 decoding is fully recursive.
32692 .vitem &$mime_part_count$&
32693 This variable is a counter that is raised for each processed MIME part. It
32694 starts at zero for the very first part (which is usually a multipart). The
32695 counter is per-message, so it is reset when processing RFC822 attachments (see
32696 &$mime_is_rfc822$&). The counter stays set after &%acl_smtp_mime%& is
32697 complete, so you can use it in the DATA ACL to determine the number of MIME
32698 parts of a message. For non-MIME messages, this variable contains the value -1.
32703 .section "Scanning with regular expressions" "SECTscanregex"
32704 .cindex "content scanning" "with regular expressions"
32705 .cindex "regular expressions" "content scanning with"
32706 You can specify your own custom regular expression matches on the full body of
32707 the message, or on individual MIME parts.
32709 The &%regex%& condition takes one or more regular expressions as arguments and
32710 matches them against the full message (when called in the DATA ACL) or a raw
32711 MIME part (when called in the MIME ACL). The &%regex%& condition matches
32712 linewise, with a maximum line length of 32K characters. That means you cannot
32713 have multiline matches with the &%regex%& condition.
32715 The &%mime_regex%& condition can be called only in the MIME ACL. It matches up
32716 to 32K of decoded content (the whole content at once, not linewise). If the
32717 part has not been decoded with the &%decode%& modifier earlier in the ACL, it
32718 is decoded automatically when &%mime_regex%& is executed (using default path
32719 and filename values). If the decoded data is larger than 32K, only the first
32720 32K characters are checked.
32722 The regular expressions are passed as a colon-separated list. To include a
32723 literal colon, you must double it. Since the whole right-hand side string is
32724 expanded before being used, you must also escape dollar signs and backslashes
32725 with more backslashes, or use the &`\N`& facility to disable expansion.
32726 Here is a simple example that contains two regular expressions:
32728 deny message = contains blacklisted regex ($regex_match_string)
32729 regex = [Mm]ortgage : URGENT BUSINESS PROPOSAL
32731 The conditions returns true if any one of the regular expressions matches. The
32732 &$regex_match_string$& expansion variable is then set up and contains the
32733 matching regular expression.
32734 The expansion variables &$regex1$& &$regex2$& etc
32735 are set to any substrings captured by the regular expression.
32737 &*Warning*&: With large messages, these conditions can be fairly
32745 . ////////////////////////////////////////////////////////////////////////////
32746 . ////////////////////////////////////////////////////////////////////////////
32748 .chapter "Adding a local scan function to Exim" "CHAPlocalscan" &&&
32749 "Local scan function"
32750 .scindex IIDlosca "&[local_scan()]& function" "description of"
32751 .cindex "customizing" "input scan using C function"
32752 .cindex "policy control" "by local scan function"
32753 In these days of email worms, viruses, and ever-increasing spam, some sites
32754 want to apply a lot of checking to messages before accepting them.
32756 The content scanning extension (chapter &<<CHAPexiscan>>&) has facilities for
32757 passing messages to external virus and spam scanning software. You can also do
32758 a certain amount in Exim itself through string expansions and the &%condition%&
32759 condition in the ACL that runs after the SMTP DATA command or the ACL for
32760 non-SMTP messages (see chapter &<<CHAPACL>>&), but this has its limitations.
32762 To allow for further customization to a site's own requirements, there is the
32763 possibility of linking Exim with a private message scanning function, written
32764 in C. If you want to run code that is written in something other than C, you
32765 can of course use a little C stub to call it.
32767 The local scan function is run once for every incoming message, at the point
32768 when Exim is just about to accept the message.
32769 It can therefore be used to control non-SMTP messages from local processes as
32770 well as messages arriving via SMTP.
32772 Exim applies a timeout to calls of the local scan function, and there is an
32773 option called &%local_scan_timeout%& for setting it. The default is 5 minutes.
32774 Zero means &"no timeout"&.
32775 Exim also sets up signal handlers for SIGSEGV, SIGILL, SIGFPE, and SIGBUS
32776 before calling the local scan function, so that the most common types of crash
32777 are caught. If the timeout is exceeded or one of those signals is caught, the
32778 incoming message is rejected with a temporary error if it is an SMTP message.
32779 For a non-SMTP message, the message is dropped and Exim ends with a non-zero
32780 code. The incident is logged on the main and reject logs.
32784 .section "Building Exim to use a local scan function" "SECID207"
32785 .cindex "&[local_scan()]& function" "building Exim to use"
32786 To make use of the local scan function feature, you must tell Exim where your
32787 function is before building Exim, by setting
32789 both HAVE_LOCAL_SCAN and
32791 LOCAL_SCAN_SOURCE in your
32792 &_Local/Makefile_&. A recommended place to put it is in the &_Local_&
32793 directory, so you might set
32795 HAVE_LOCAL_SCAN=yes
32796 LOCAL_SCAN_SOURCE=Local/local_scan.c
32798 for example. The function must be called &[local_scan()]&. It is called by
32799 Exim after it has received a message, when the success return code is about to
32800 be sent. This is after all the ACLs have been run. The return code from your
32801 function controls whether the message is actually accepted or not. There is a
32802 commented template function (that just accepts the message) in the file
32803 _src/local_scan.c_.
32805 If you want to make use of Exim's run time configuration file to set options
32806 for your &[local_scan()]& function, you must also set
32808 LOCAL_SCAN_HAS_OPTIONS=yes
32810 in &_Local/Makefile_& (see section &<<SECTconoptloc>>& below).
32815 .section "API for local_scan()" "SECTapiforloc"
32816 .cindex "&[local_scan()]& function" "API description"
32817 You must include this line near the start of your code:
32819 #include "local_scan.h"
32821 This header file defines a number of variables and other values, and the
32822 prototype for the function itself. Exim is coded to use unsigned char values
32823 almost exclusively, and one of the things this header defines is a shorthand
32824 for &`unsigned char`& called &`uschar`&.
32825 It also contains the following macro definitions, to simplify casting character
32826 strings and pointers to character strings:
32828 #define CS (char *)
32829 #define CCS (const char *)
32830 #define CSS (char **)
32831 #define US (unsigned char *)
32832 #define CUS (const unsigned char *)
32833 #define USS (unsigned char **)
32835 The function prototype for &[local_scan()]& is:
32837 extern int local_scan(int fd, uschar **return_text);
32839 The arguments are as follows:
32842 &%fd%& is a file descriptor for the file that contains the body of the message
32843 (the -D file). The file is open for reading and writing, but updating it is not
32844 recommended. &*Warning*&: You must &'not'& close this file descriptor.
32846 The descriptor is positioned at character 19 of the file, which is the first
32847 character of the body itself, because the first 19 characters are the message
32848 id followed by &`-D`& and a newline. If you rewind the file, you should use the
32849 macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in
32850 case this changes in some future version.
32852 &%return_text%& is an address which you can use to return a pointer to a text
32853 string at the end of the function. The value it points to on entry is NULL.
32856 The function must return an &%int%& value which is one of the following macros:
32859 .vitem &`LOCAL_SCAN_ACCEPT`&
32860 .vindex "&$local_scan_data$&"
32861 The message is accepted. If you pass back a string of text, it is saved with
32862 the message, and made available in the variable &$local_scan_data$&. No
32863 newlines are permitted (if there are any, they are turned into spaces) and the
32864 maximum length of text is 1000 characters.
32866 .vitem &`LOCAL_SCAN_ACCEPT_FREEZE`&
32867 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
32868 queued without immediate delivery, and is frozen.
32870 .vitem &`LOCAL_SCAN_ACCEPT_QUEUE`&
32871 This behaves as LOCAL_SCAN_ACCEPT, except that the accepted message is
32872 queued without immediate delivery.
32874 .vitem &`LOCAL_SCAN_REJECT`&
32875 The message is rejected; the returned text is used as an error message which is
32876 passed back to the sender and which is also logged. Newlines are permitted &--
32877 they cause a multiline response for SMTP rejections, but are converted to
32878 &`\n`& in log lines. If no message is given, &"Administrative prohibition"& is
32881 .vitem &`LOCAL_SCAN_TEMPREJECT`&
32882 The message is temporarily rejected; the returned text is used as an error
32883 message as for LOCAL_SCAN_REJECT. If no message is given, &"Temporary local
32886 .vitem &`LOCAL_SCAN_REJECT_NOLOGHDR`&
32887 This behaves as LOCAL_SCAN_REJECT, except that the header of the rejected
32888 message is not written to the reject log. It has the effect of unsetting the
32889 &%rejected_header%& log selector for just this rejection. If
32890 &%rejected_header%& is already unset (see the discussion of the
32891 &%log_selection%& option in section &<<SECTlogselector>>&), this code is the
32892 same as LOCAL_SCAN_REJECT.
32894 .vitem &`LOCAL_SCAN_TEMPREJECT_NOLOGHDR`&
32895 This code is a variation of LOCAL_SCAN_TEMPREJECT in the same way that
32896 LOCAL_SCAN_REJECT_NOLOGHDR is a variation of LOCAL_SCAN_REJECT.
32899 If the message is not being received by interactive SMTP, rejections are
32900 reported by writing to &%stderr%& or by sending an email, as configured by the
32901 &%-oe%& command line options.
32905 .section "Configuration options for local_scan()" "SECTconoptloc"
32906 .cindex "&[local_scan()]& function" "configuration options"
32907 It is possible to have option settings in the main configuration file
32908 that set values in static variables in the &[local_scan()]& module. If you
32909 want to do this, you must have the line
32911 LOCAL_SCAN_HAS_OPTIONS=yes
32913 in your &_Local/Makefile_& when you build Exim. (This line is in
32914 &_OS/Makefile-Default_&, commented out). Then, in the &[local_scan()]& source
32915 file, you must define static variables to hold the option values, and a table
32918 The table must be a vector called &%local_scan_options%&, of type
32919 &`optionlist`&. Each entry is a triplet, consisting of a name, an option type,
32920 and a pointer to the variable that holds the value. The entries must appear in
32921 alphabetical order. Following &%local_scan_options%& you must also define a
32922 variable called &%local_scan_options_count%& that contains the number of
32923 entries in the table. Here is a short example, showing two kinds of option:
32925 static int my_integer_option = 42;
32926 static uschar *my_string_option = US"a default string";
32928 optionlist local_scan_options[] = {
32929 { "my_integer", opt_int, &my_integer_option },
32930 { "my_string", opt_stringptr, &my_string_option }
32933 int local_scan_options_count =
32934 sizeof(local_scan_options)/sizeof(optionlist);
32936 The values of the variables can now be changed from Exim's runtime
32937 configuration file by including a local scan section as in this example:
32941 my_string = some string of text...
32943 The available types of option data are as follows:
32946 .vitem &*opt_bool*&
32947 This specifies a boolean (true/false) option. The address should point to a
32948 variable of type &`BOOL`&, which will be set to TRUE or FALSE, which are macros
32949 that are defined as &"1"& and &"0"&, respectively. If you want to detect
32950 whether such a variable has been set at all, you can initialize it to
32951 TRUE_UNSET. (BOOL variables are integers underneath, so can hold more than two
32954 .vitem &*opt_fixed*&
32955 This specifies a fixed point number, such as is used for load averages.
32956 The address should point to a variable of type &`int`&. The value is stored
32957 multiplied by 1000, so, for example, 1.4142 is truncated and stored as 1414.
32960 This specifies an integer; the address should point to a variable of type
32961 &`int`&. The value may be specified in any of the integer formats accepted by
32964 .vitem &*opt_mkint*&
32965 This is the same as &%opt_int%&, except that when such a value is output in a
32966 &%-bP%& listing, if it is an exact number of kilobytes or megabytes, it is
32967 printed with the suffix K or M.
32969 .vitem &*opt_octint*&
32970 This also specifies an integer, but the value is always interpreted as an
32971 octal integer, whether or not it starts with the digit zero, and it is
32972 always output in octal.
32974 .vitem &*opt_stringptr*&
32975 This specifies a string value; the address must be a pointer to a
32976 variable that points to a string (for example, of type &`uschar *`&).
32978 .vitem &*opt_time*&
32979 This specifies a time interval value. The address must point to a variable of
32980 type &`int`&. The value that is placed there is a number of seconds.
32983 If the &%-bP%& command line option is followed by &`local_scan`&, Exim prints
32984 out the values of all the &[local_scan()]& options.
32988 .section "Available Exim variables" "SECID208"
32989 .cindex "&[local_scan()]& function" "available Exim variables"
32990 The header &_local_scan.h_& gives you access to a number of C variables. These
32991 are the only ones that are guaranteed to be maintained from release to release.
32992 Note, however, that you can obtain the value of any Exim expansion variable,
32993 including &$recipients$&, by calling &'expand_string()'&. The exported
32994 C variables are as follows:
32997 .vitem &*int&~body_linecount*&
32998 This variable contains the number of lines in the message's body.
32999 It is not valid if the &%spool_files_wireformat%& option is used.
33001 .vitem &*int&~body_zerocount*&
33002 This variable contains the number of binary zero bytes in the message's body.
33003 It is not valid if the &%spool_files_wireformat%& option is used.
33005 .vitem &*unsigned&~int&~debug_selector*&
33006 This variable is set to zero when no debugging is taking place. Otherwise, it
33007 is a bitmap of debugging selectors. Two bits are identified for use in
33008 &[local_scan()]&; they are defined as macros:
33011 The &`D_v`& bit is set when &%-v%& was present on the command line. This is a
33012 testing option that is not privileged &-- any caller may set it. All the
33013 other selector bits can be set only by admin users.
33016 The &`D_local_scan`& bit is provided for use by &[local_scan()]&; it is set
33017 by the &`+local_scan`& debug selector. It is not included in the default set
33021 Thus, to write to the debugging output only when &`+local_scan`& has been
33022 selected, you should use code like this:
33024 if ((debug_selector & D_local_scan) != 0)
33025 debug_printf("xxx", ...);
33027 .vitem &*uschar&~*expand_string_message*&
33028 After a failing call to &'expand_string()'& (returned value NULL), the
33029 variable &%expand_string_message%& contains the error message, zero-terminated.
33031 .vitem &*header_line&~*header_list*&
33032 A pointer to a chain of header lines. The &%header_line%& structure is
33035 .vitem &*header_line&~*header_last*&
33036 A pointer to the last of the header lines.
33038 .vitem &*uschar&~*headers_charset*&
33039 The value of the &%headers_charset%& configuration option.
33041 .vitem &*BOOL&~host_checking*&
33042 This variable is TRUE during a host checking session that is initiated by the
33043 &%-bh%& command line option.
33045 .vitem &*uschar&~*interface_address*&
33046 The IP address of the interface that received the message, as a string. This
33047 is NULL for locally submitted messages.
33049 .vitem &*int&~interface_port*&
33050 The port on which this message was received. When testing with the &%-bh%&
33051 command line option, the value of this variable is -1 unless a port has been
33052 specified via the &%-oMi%& option.
33054 .vitem &*uschar&~*message_id*&
33055 This variable contains Exim's message id for the incoming message (the value of
33056 &$message_exim_id$&) as a zero-terminated string.
33058 .vitem &*uschar&~*received_protocol*&
33059 The name of the protocol by which the message was received.
33061 .vitem &*int&~recipients_count*&
33062 The number of accepted recipients.
33064 .vitem &*recipient_item&~*recipients_list*&
33065 .cindex "recipient" "adding in local scan"
33066 .cindex "recipient" "removing in local scan"
33067 The list of accepted recipients, held in a vector of length
33068 &%recipients_count%&. The &%recipient_item%& structure is discussed below. You
33069 can add additional recipients by calling &'receive_add_recipient()'& (see
33070 below). You can delete recipients by removing them from the vector and
33071 adjusting the value in &%recipients_count%&. In particular, by setting
33072 &%recipients_count%& to zero you remove all recipients. If you then return the
33073 value &`LOCAL_SCAN_ACCEPT`&, the message is accepted, but immediately
33074 blackholed. To replace the recipients, you can set &%recipients_count%& to zero
33075 and then call &'receive_add_recipient()'& as often as needed.
33077 .vitem &*uschar&~*sender_address*&
33078 The envelope sender address. For bounce messages this is the empty string.
33080 .vitem &*uschar&~*sender_host_address*&
33081 The IP address of the sending host, as a string. This is NULL for
33082 locally-submitted messages.
33084 .vitem &*uschar&~*sender_host_authenticated*&
33085 The name of the authentication mechanism that was used, or NULL if the message
33086 was not received over an authenticated SMTP connection.
33088 .vitem &*uschar&~*sender_host_name*&
33089 The name of the sending host, if known.
33091 .vitem &*int&~sender_host_port*&
33092 The port on the sending host.
33094 .vitem &*BOOL&~smtp_input*&
33095 This variable is TRUE for all SMTP input, including BSMTP.
33097 .vitem &*BOOL&~smtp_batched_input*&
33098 This variable is TRUE for BSMTP input.
33100 .vitem &*int&~store_pool*&
33101 The contents of this variable control which pool of memory is used for new
33102 requests. See section &<<SECTmemhanloc>>& for details.
33106 .section "Structure of header lines" "SECID209"
33107 The &%header_line%& structure contains the members listed below.
33108 You can add additional header lines by calling the &'header_add()'& function
33109 (see below). You can cause header lines to be ignored (deleted) by setting
33114 .vitem &*struct&~header_line&~*next*&
33115 A pointer to the next header line, or NULL for the last line.
33117 .vitem &*int&~type*&
33118 A code identifying certain headers that Exim recognizes. The codes are printing
33119 characters, and are documented in chapter &<<CHAPspool>>& of this manual.
33120 Notice in particular that any header line whose type is * is not transmitted
33121 with the message. This flagging is used for header lines that have been
33122 rewritten, or are to be removed (for example, &'Envelope-sender:'& header
33123 lines.) Effectively, * means &"deleted"&.
33125 .vitem &*int&~slen*&
33126 The number of characters in the header line, including the terminating and any
33129 .vitem &*uschar&~*text*&
33130 A pointer to the text of the header. It always ends with a newline, followed by
33131 a zero byte. Internal newlines are preserved.
33136 .section "Structure of recipient items" "SECID210"
33137 The &%recipient_item%& structure contains these members:
33140 .vitem &*uschar&~*address*&
33141 This is a pointer to the recipient address as it was received.
33143 .vitem &*int&~pno*&
33144 This is used in later Exim processing when top level addresses are created by
33145 the &%one_time%& option. It is not relevant at the time &[local_scan()]& is run
33146 and must always contain -1 at this stage.
33148 .vitem &*uschar&~*errors_to*&
33149 If this value is not NULL, bounce messages caused by failing to deliver to the
33150 recipient are sent to the address it contains. In other words, it overrides the
33151 envelope sender for this one recipient. (Compare the &%errors_to%& generic
33152 router option.) If a &[local_scan()]& function sets an &%errors_to%& field to
33153 an unqualified address, Exim qualifies it using the domain from
33154 &%qualify_recipient%&. When &[local_scan()]& is called, the &%errors_to%& field
33155 is NULL for all recipients.
33160 .section "Available Exim functions" "SECID211"
33161 .cindex "&[local_scan()]& function" "available Exim functions"
33162 The header &_local_scan.h_& gives you access to a number of Exim functions.
33163 These are the only ones that are guaranteed to be maintained from release to
33167 .vitem "&*pid_t&~child_open(uschar&~**argv,&~uschar&~**envp,&~int&~newumask,&&&
33168 &~int&~*infdptr,&~int&~*outfdptr, &~&~BOOL&~make_leader)*&"
33170 This function creates a child process that runs the command specified by
33171 &%argv%&. The environment for the process is specified by &%envp%&, which can
33172 be NULL if no environment variables are to be passed. A new umask is supplied
33173 for the process in &%newumask%&.
33175 Pipes to the standard input and output of the new process are set up
33176 and returned to the caller via the &%infdptr%& and &%outfdptr%& arguments. The
33177 standard error is cloned to the standard output. If there are any file
33178 descriptors &"in the way"& in the new process, they are closed. If the final
33179 argument is TRUE, the new process is made into a process group leader.
33181 The function returns the pid of the new process, or -1 if things go wrong.
33183 .vitem &*int&~child_close(pid_t&~pid,&~int&~timeout)*&
33184 This function waits for a child process to terminate, or for a timeout (in
33185 seconds) to expire. A timeout value of zero means wait as long as it takes. The
33186 return value is as follows:
33191 The process terminated by a normal exit and the value is the process
33197 The process was terminated by a signal and the value is the negation of the
33203 The process timed out.
33207 The was some other error in wait(); &%errno%& is still set.
33210 .vitem &*pid_t&~child_open_exim(int&~*fd)*&
33211 This function provide you with a means of submitting a new message to
33212 Exim. (Of course, you can also call &_/usr/sbin/sendmail_& yourself if you
33213 want, but this packages it all up for you.) The function creates a pipe,
33214 forks a subprocess that is running
33216 exim -t -oem -oi -f <>
33218 and returns to you (via the &`int *`& argument) a file descriptor for the pipe
33219 that is connected to the standard input. The yield of the function is the PID
33220 of the subprocess. You can then write a message to the file descriptor, with
33221 recipients in &'To:'&, &'Cc:'&, and/or &'Bcc:'& header lines.
33223 When you have finished, call &'child_close()'& to wait for the process to
33224 finish and to collect its ending status. A timeout value of zero is usually
33225 fine in this circumstance. Unless you have made a mistake with the recipient
33226 addresses, you should get a return code of zero.
33229 .vitem &*pid_t&~child_open_exim2(int&~*fd,&~uschar&~*sender,&~uschar&~&&&
33230 *sender_authentication)*&
33231 This function is a more sophisticated version of &'child_open()'&. The command
33234 &`exim -t -oem -oi -f `&&'sender'&&` -oMas `&&'sender_authentication'&
33236 The third argument may be NULL, in which case the &%-oMas%& option is omitted.
33239 .vitem &*void&~debug_printf(char&~*,&~...)*&
33240 This is Exim's debugging function, with arguments as for &'(printf()'&. The
33241 output is written to the standard error stream. If no debugging is selected,
33242 calls to &'debug_printf()'& have no effect. Normally, you should make calls
33243 conditional on the &`local_scan`& debug selector by coding like this:
33245 if ((debug_selector & D_local_scan) != 0)
33246 debug_printf("xxx", ...);
33249 .vitem &*uschar&~*expand_string(uschar&~*string)*&
33250 This is an interface to Exim's string expansion code. The return value is the
33251 expanded string, or NULL if there was an expansion failure.
33252 The C variable &%expand_string_message%& contains an error message after an
33253 expansion failure. If expansion does not change the string, the return value is
33254 the pointer to the input string. Otherwise, the return value points to a new
33255 block of memory that was obtained by a call to &'store_get()'&. See section
33256 &<<SECTmemhanloc>>& below for a discussion of memory handling.
33258 .vitem &*void&~header_add(int&~type,&~char&~*format,&~...)*&
33259 This function allows you to an add additional header line at the end of the
33260 existing ones. The first argument is the type, and should normally be a space
33261 character. The second argument is a format string and any number of
33262 substitution arguments as for &[sprintf()]&. You may include internal newlines
33263 if you want, and you must ensure that the string ends with a newline.
33265 .vitem "&*void&~header_add_at_position(BOOL&~after,&~uschar&~*name,&~&&&
33266 BOOL&~topnot,&~int&~type,&~char&~*format, &~&~...)*&"
33267 This function adds a new header line at a specified point in the header
33268 chain. The header itself is specified as for &'header_add()'&.
33270 If &%name%& is NULL, the new header is added at the end of the chain if
33271 &%after%& is true, or at the start if &%after%& is false. If &%name%& is not
33272 NULL, the header lines are searched for the first non-deleted header that
33273 matches the name. If one is found, the new header is added before it if
33274 &%after%& is false. If &%after%& is true, the new header is added after the
33275 found header and any adjacent subsequent ones with the same name (even if
33276 marked &"deleted"&). If no matching non-deleted header is found, the &%topnot%&
33277 option controls where the header is added. If it is true, addition is at the
33278 top; otherwise at the bottom. Thus, to add a header after all the &'Received:'&
33279 headers, or at the top if there are no &'Received:'& headers, you could use
33281 header_add_at_position(TRUE, US"Received", TRUE,
33282 ' ', "X-xxx: ...");
33284 Normally, there is always at least one non-deleted &'Received:'& header, but
33285 there may not be if &%received_header_text%& expands to an empty string.
33288 .vitem &*void&~header_remove(int&~occurrence,&~uschar&~*name)*&
33289 This function removes header lines. If &%occurrence%& is zero or negative, all
33290 occurrences of the header are removed. If occurrence is greater than zero, that
33291 particular instance of the header is removed. If no header(s) can be found that
33292 match the specification, the function does nothing.
33295 .vitem "&*BOOL&~header_testname(header_line&~*hdr,&~uschar&~*name,&~&&&
33296 int&~length,&~BOOL&~notdel)*&"
33297 This function tests whether the given header has the given name. It is not just
33298 a string comparison, because white space is permitted between the name and the
33299 colon. If the &%notdel%& argument is true, a false return is forced for all
33300 &"deleted"& headers; otherwise they are not treated specially. For example:
33302 if (header_testname(h, US"X-Spam", 6, TRUE)) ...
33304 .vitem &*uschar&~*lss_b64encode(uschar&~*cleartext,&~int&~length)*&
33305 .cindex "base64 encoding" "functions for &[local_scan()]& use"
33306 This function base64-encodes a string, which is passed by address and length.
33307 The text may contain bytes of any value, including zero. The result is passed
33308 back in dynamic memory that is obtained by calling &'store_get()'&. It is
33311 .vitem &*int&~lss_b64decode(uschar&~*codetext,&~uschar&~**cleartext)*&
33312 This function decodes a base64-encoded string. Its arguments are a
33313 zero-terminated base64-encoded string and the address of a variable that is set
33314 to point to the result, which is in dynamic memory. The length of the decoded
33315 string is the yield of the function. If the input is invalid base64 data, the
33316 yield is -1. A zero byte is added to the end of the output string to make it
33317 easy to interpret as a C string (assuming it contains no zeros of its own). The
33318 added zero byte is not included in the returned count.
33320 .vitem &*int&~lss_match_domain(uschar&~*domain,&~uschar&~*list)*&
33321 This function checks for a match in a domain list. Domains are always
33322 matched caselessly. The return value is one of the following:
33324 &`OK `& match succeeded
33325 &`FAIL `& match failed
33326 &`DEFER `& match deferred
33328 DEFER is usually caused by some kind of lookup defer, such as the
33329 inability to contact a database.
33331 .vitem "&*int&~lss_match_local_part(uschar&~*localpart,&~uschar&~*list,&~&&&
33333 This function checks for a match in a local part list. The third argument
33334 controls case-sensitivity. The return values are as for
33335 &'lss_match_domain()'&.
33337 .vitem "&*int&~lss_match_address(uschar&~*address,&~uschar&~*list,&~&&&
33339 This function checks for a match in an address list. The third argument
33340 controls the case-sensitivity of the local part match. The domain is always
33341 matched caselessly. The return values are as for &'lss_match_domain()'&.
33343 .vitem "&*int&~lss_match_host(uschar&~*host_name,&~uschar&~*host_address,&~&&&
33345 This function checks for a match in a host list. The most common usage is
33348 lss_match_host(sender_host_name, sender_host_address, ...)
33350 .vindex "&$sender_host_address$&"
33351 An empty address field matches an empty item in the host list. If the host name
33352 is NULL, the name corresponding to &$sender_host_address$& is automatically
33353 looked up if a host name is required to match an item in the list. The return
33354 values are as for &'lss_match_domain()'&, but in addition, &'lss_match_host()'&
33355 returns ERROR in the case when it had to look up a host name, but the lookup
33358 .vitem "&*void&~log_write(unsigned&~int&~selector,&~int&~which,&~char&~&&&
33360 This function writes to Exim's log files. The first argument should be zero (it
33361 is concerned with &%log_selector%&). The second argument can be &`LOG_MAIN`& or
33362 &`LOG_REJECT`& or &`LOG_PANIC`& or the inclusive &"or"& of any combination of
33363 them. It specifies to which log or logs the message is written. The remaining
33364 arguments are a format and relevant insertion arguments. The string should not
33365 contain any newlines, not even at the end.
33368 .vitem &*void&~receive_add_recipient(uschar&~*address,&~int&~pno)*&
33369 This function adds an additional recipient to the message. The first argument
33370 is the recipient address. If it is unqualified (has no domain), it is qualified
33371 with the &%qualify_recipient%& domain. The second argument must always be -1.
33373 This function does not allow you to specify a private &%errors_to%& address (as
33374 described with the structure of &%recipient_item%& above), because it pre-dates
33375 the addition of that field to the structure. However, it is easy to add such a
33376 value afterwards. For example:
33378 receive_add_recipient(US"monitor@mydom.example", -1);
33379 recipients_list[recipients_count-1].errors_to =
33380 US"postmaster@mydom.example";
33383 .vitem &*BOOL&~receive_remove_recipient(uschar&~*recipient)*&
33384 This is a convenience function to remove a named recipient from the list of
33385 recipients. It returns true if a recipient was removed, and false if no
33386 matching recipient could be found. The argument must be a complete email
33393 .vitem "&*uschar&~rfc2047_decode(uschar&~*string,&~BOOL&~lencheck,&&&
33394 &~uschar&~*target,&~int&~zeroval,&~int&~*lenptr, &~&~uschar&~**error)*&"
33395 This function decodes strings that are encoded according to RFC 2047. Typically
33396 these are the contents of header lines. First, each &"encoded word"& is decoded
33397 from the Q or B encoding into a byte-string. Then, if provided with the name of
33398 a charset encoding, and if the &[iconv()]& function is available, an attempt is
33399 made to translate the result to the named character set. If this fails, the
33400 binary string is returned with an error message.
33402 The first argument is the string to be decoded. If &%lencheck%& is TRUE, the
33403 maximum MIME word length is enforced. The third argument is the target
33404 encoding, or NULL if no translation is wanted.
33406 .cindex "binary zero" "in RFC 2047 decoding"
33407 .cindex "RFC 2047" "binary zero in"
33408 If a binary zero is encountered in the decoded string, it is replaced by the
33409 contents of the &%zeroval%& argument. For use with Exim headers, the value must
33410 not be 0 because header lines are handled as zero-terminated strings.
33412 The function returns the result of processing the string, zero-terminated; if
33413 &%lenptr%& is not NULL, the length of the result is set in the variable to
33414 which it points. When &%zeroval%& is 0, &%lenptr%& should not be NULL.
33416 If an error is encountered, the function returns NULL and uses the &%error%&
33417 argument to return an error message. The variable pointed to by &%error%& is
33418 set to NULL if there is no error; it may be set non-NULL even when the function
33419 returns a non-NULL value if decoding was successful, but there was a problem
33423 .vitem &*int&~smtp_fflush(void)*&
33424 This function is used in conjunction with &'smtp_printf()'&, as described
33427 .vitem &*void&~smtp_printf(char&~*,&~...)*&
33428 The arguments of this function are like &[printf()]&; it writes to the SMTP
33429 output stream. You should use this function only when there is an SMTP output
33430 stream, that is, when the incoming message is being received via interactive
33431 SMTP. This is the case when &%smtp_input%& is TRUE and &%smtp_batched_input%&
33432 is FALSE. If you want to test for an incoming message from another host (as
33433 opposed to a local process that used the &%-bs%& command line option), you can
33434 test the value of &%sender_host_address%&, which is non-NULL when a remote host
33437 If an SMTP TLS connection is established, &'smtp_printf()'& uses the TLS
33438 output function, so it can be used for all forms of SMTP connection.
33440 Strings that are written by &'smtp_printf()'& from within &[local_scan()]&
33441 must start with an appropriate response code: 550 if you are going to return
33442 LOCAL_SCAN_REJECT, 451 if you are going to return
33443 LOCAL_SCAN_TEMPREJECT, and 250 otherwise. Because you are writing the
33444 initial lines of a multi-line response, the code must be followed by a hyphen
33445 to indicate that the line is not the final response line. You must also ensure
33446 that the lines you write terminate with CRLF. For example:
33448 smtp_printf("550-this is some extra info\r\n");
33449 return LOCAL_SCAN_REJECT;
33451 Note that you can also create multi-line responses by including newlines in
33452 the data returned via the &%return_text%& argument. The added value of using
33453 &'smtp_printf()'& is that, for instance, you could introduce delays between
33454 multiple output lines.
33456 The &'smtp_printf()'& function does not return any error indication, because it
33457 does not automatically flush pending output, and therefore does not test
33458 the state of the stream. (In the main code of Exim, flushing and error
33459 detection is done when Exim is ready for the next SMTP input command.) If
33460 you want to flush the output and check for an error (for example, the
33461 dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no
33462 arguments. It flushes the output stream, and returns a non-zero value if there
33465 .vitem &*void&~*store_get(int)*&
33466 This function accesses Exim's internal store (memory) manager. It gets a new
33467 chunk of memory whose size is given by the argument. Exim bombs out if it ever
33468 runs out of memory. See the next section for a discussion of memory handling.
33470 .vitem &*void&~*store_get_perm(int)*&
33471 This function is like &'store_get()'&, but it always gets memory from the
33472 permanent pool. See the next section for a discussion of memory handling.
33474 .vitem &*uschar&~*string_copy(uschar&~*string)*&
33477 .vitem &*uschar&~*string_copyn(uschar&~*string,&~int&~length)*&
33480 .vitem &*uschar&~*string_sprintf(char&~*format,&~...)*&
33481 These three functions create strings using Exim's dynamic memory facilities.
33482 The first makes a copy of an entire string. The second copies up to a maximum
33483 number of characters, indicated by the second argument. The third uses a format
33484 and insertion arguments to create a new string. In each case, the result is a
33485 pointer to a new string in the current memory pool. See the next section for
33491 .section "More about Exim's memory handling" "SECTmemhanloc"
33492 .cindex "&[local_scan()]& function" "memory handling"
33493 No function is provided for freeing memory, because that is never needed.
33494 The dynamic memory that Exim uses when receiving a message is automatically
33495 recycled if another message is received by the same process (this applies only
33496 to incoming SMTP connections &-- other input methods can supply only one
33497 message at a time). After receiving the last message, a reception process
33500 Because it is recycled, the normal dynamic memory cannot be used for holding
33501 data that must be preserved over a number of incoming messages on the same SMTP
33502 connection. However, Exim in fact uses two pools of dynamic memory; the second
33503 one is not recycled, and can be used for this purpose.
33505 If you want to allocate memory that remains available for subsequent messages
33506 in the same SMTP connection, you should set
33508 store_pool = POOL_PERM
33510 before calling the function that does the allocation. There is no need to
33511 restore the value if you do not need to; however, if you do want to revert to
33512 the normal pool, you can either restore the previous value of &%store_pool%& or
33513 set it explicitly to POOL_MAIN.
33515 The pool setting applies to all functions that get dynamic memory, including
33516 &'expand_string()'&, &'store_get()'&, and the &'string_xxx()'& functions.
33517 There is also a convenience function called &'store_get_perm()'& that gets a
33518 block of memory from the permanent pool while preserving the value of
33525 . ////////////////////////////////////////////////////////////////////////////
33526 . ////////////////////////////////////////////////////////////////////////////
33528 .chapter "System-wide message filtering" "CHAPsystemfilter"
33529 .scindex IIDsysfil1 "filter" "system filter"
33530 .scindex IIDsysfil2 "filtering all mail"
33531 .scindex IIDsysfil3 "system filter"
33532 The previous chapters (on ACLs and the local scan function) describe checks
33533 that can be applied to messages before they are accepted by a host. There is
33534 also a mechanism for checking messages once they have been received, but before
33535 they are delivered. This is called the &'system filter'&.
33537 The system filter operates in a similar manner to users' filter files, but it
33538 is run just once per message (however many recipients the message has).
33539 It should not normally be used as a substitute for routing, because &%deliver%&
33540 commands in a system router provide new envelope recipient addresses.
33541 The system filter must be an Exim filter. It cannot be a Sieve filter.
33543 The system filter is run at the start of a delivery attempt, before any routing
33544 is done. If a message fails to be completely delivered at the first attempt,
33545 the system filter is run again at the start of every retry.
33546 If you want your filter to do something only once per message, you can make use
33547 of the &%first_delivery%& condition in an &%if%& command in the filter to
33548 prevent it happening on retries.
33550 .vindex "&$domain$&"
33551 .vindex "&$local_part$&"
33552 &*Warning*&: Because the system filter runs just once, variables that are
33553 specific to individual recipient addresses, such as &$local_part$& and
33554 &$domain$&, are not set, and the &"personal"& condition is not meaningful. If
33555 you want to run a centrally-specified filter for each recipient address
33556 independently, you can do so by setting up a suitable &(redirect)& router, as
33557 described in section &<<SECTperaddfil>>& below.
33560 .section "Specifying a system filter" "SECID212"
33561 .cindex "uid (user id)" "system filter"
33562 .cindex "gid (group id)" "system filter"
33563 The name of the file that contains the system filter must be specified by
33564 setting &%system_filter%&. If you want the filter to run under a uid and gid
33565 other than root, you must also set &%system_filter_user%& and
33566 &%system_filter_group%& as appropriate. For example:
33568 system_filter = /etc/mail/exim.filter
33569 system_filter_user = exim
33571 If a system filter generates any deliveries directly to files or pipes (via the
33572 &%save%& or &%pipe%& commands), transports to handle these deliveries must be
33573 specified by setting &%system_filter_file_transport%& and
33574 &%system_filter_pipe_transport%&, respectively. Similarly,
33575 &%system_filter_reply_transport%& must be set to handle any messages generated
33576 by the &%reply%& command.
33579 .section "Testing a system filter" "SECID213"
33580 You can run simple tests of a system filter in the same way as for a user
33581 filter, but you should use &%-bF%& rather than &%-bf%&, so that features that
33582 are permitted only in system filters are recognized.
33584 If you want to test the combined effect of a system filter and a user filter,
33585 you can use both &%-bF%& and &%-bf%& on the same command line.
33589 .section "Contents of a system filter" "SECID214"
33590 The language used to specify system filters is the same as for users' filter
33591 files. It is described in the separate end-user document &'Exim's interface to
33592 mail filtering'&. However, there are some additional features that are
33593 available only in system filters; these are described in subsequent sections.
33594 If they are encountered in a user's filter file or when testing with &%-bf%&,
33597 .cindex "frozen messages" "manual thaw; testing in filter"
33598 There are two special conditions which, though available in users' filter
33599 files, are designed for use in system filters. The condition &%first_delivery%&
33600 is true only for the first attempt at delivering a message, and
33601 &%manually_thawed%& is true only if the message has been frozen, and
33602 subsequently thawed by an admin user. An explicit forced delivery counts as a
33603 manual thaw, but thawing as a result of the &%auto_thaw%& setting does not.
33605 &*Warning*&: If a system filter uses the &%first_delivery%& condition to
33606 specify an &"unseen"& (non-significant) delivery, and that delivery does not
33607 succeed, it will not be tried again.
33608 If you want Exim to retry an unseen delivery until it succeeds, you should
33609 arrange to set it up every time the filter runs.
33611 When a system filter finishes running, the values of the variables &$n0$& &--
33612 &$n9$& are copied into &$sn0$& &-- &$sn9$& and are thereby made available to
33613 users' filter files. Thus a system filter can, for example, set up &"scores"&
33614 to which users' filter files can refer.
33618 .section "Additional variable for system filters" "SECID215"
33619 .vindex "&$recipients$&"
33620 The expansion variable &$recipients$&, containing a list of all the recipients
33621 of the message (separated by commas and white space), is available in system
33622 filters. It is not available in users' filters for privacy reasons.
33626 .section "Defer, freeze, and fail commands for system filters" "SECID216"
33627 .cindex "freezing messages"
33628 .cindex "message" "freezing"
33629 .cindex "message" "forced failure"
33630 .cindex "&%fail%&" "in system filter"
33631 .cindex "&%freeze%& in system filter"
33632 .cindex "&%defer%& in system filter"
33633 There are three extra commands (&%defer%&, &%freeze%& and &%fail%&) which are
33634 always available in system filters, but are not normally enabled in users'
33635 filters. (See the &%allow_defer%&, &%allow_freeze%& and &%allow_fail%& options
33636 for the &(redirect)& router.) These commands can optionally be followed by the
33637 word &%text%& and a string containing an error message, for example:
33639 fail text "this message looks like spam to me"
33641 The keyword &%text%& is optional if the next character is a double quote.
33643 The &%defer%& command defers delivery of the original recipients of the
33644 message. The &%fail%& command causes all the original recipients to be failed,
33645 and a bounce message to be created. The &%freeze%& command suspends all
33646 delivery attempts for the original recipients. In all cases, any new deliveries
33647 that are specified by the filter are attempted as normal after the filter has
33650 The &%freeze%& command is ignored if the message has been manually unfrozen and
33651 not manually frozen since. This means that automatic freezing by a system
33652 filter can be used as a way of checking out suspicious messages. If a message
33653 is found to be all right, manually unfreezing it allows it to be delivered.
33655 .cindex "log" "&%fail%& command log line"
33656 .cindex "&%fail%&" "log line; reducing"
33657 The text given with a fail command is used as part of the bounce message as
33658 well as being written to the log. If the message is quite long, this can fill
33659 up a lot of log space when such failures are common. To reduce the size of the
33660 log message, Exim interprets the text in a special way if it starts with the
33661 two characters &`<<`& and contains &`>>`& later. The text between these two
33662 strings is written to the log, and the rest of the text is used in the bounce
33663 message. For example:
33665 fail "<<filter test 1>>Your message is rejected \
33666 because it contains attachments that we are \
33667 not prepared to receive."
33670 .cindex "loop" "caused by &%fail%&"
33671 Take great care with the &%fail%& command when basing the decision to fail on
33672 the contents of the message, because the bounce message will of course include
33673 the contents of the original message and will therefore trigger the &%fail%&
33674 command again (causing a mail loop) unless steps are taken to prevent this.
33675 Testing the &%error_message%& condition is one way to prevent this. You could
33678 if $message_body contains "this is spam" and not error_message
33679 then fail text "spam is not wanted here" endif
33681 though of course that might let through unwanted bounce messages. The
33682 alternative is clever checking of the body and/or headers to detect bounces
33683 generated by the filter.
33685 The interpretation of a system filter file ceases after a
33687 &%freeze%&, or &%fail%& command is obeyed. However, any deliveries that were
33688 set up earlier in the filter file are honoured, so you can use a sequence such
33694 to send a specified message when the system filter is freezing (or deferring or
33695 failing) a message. The normal deliveries for the message do not, of course,
33700 .section "Adding and removing headers in a system filter" "SECTaddremheasys"
33701 .cindex "header lines" "adding; in system filter"
33702 .cindex "header lines" "removing; in system filter"
33703 .cindex "filter" "header lines; adding/removing"
33704 Two filter commands that are available only in system filters are:
33706 headers add <string>
33707 headers remove <string>
33709 The argument for the &%headers add%& is a string that is expanded and then
33710 added to the end of the message's headers. It is the responsibility of the
33711 filter maintainer to make sure it conforms to RFC 2822 syntax. Leading white
33712 space is ignored, and if the string is otherwise empty, or if the expansion is
33713 forced to fail, the command has no effect.
33715 You can use &"\n"& within the string, followed by white space, to specify
33716 continued header lines. More than one header may be added in one command by
33717 including &"\n"& within the string without any following white space. For
33720 headers add "X-header-1: ....\n \
33721 continuation of X-header-1 ...\n\
33724 Note that the header line continuation white space after the first newline must
33725 be placed before the backslash that continues the input string, because white
33726 space after input continuations is ignored.
33728 The argument for &%headers remove%& is a colon-separated list of header names.
33729 This command applies only to those headers that are stored with the message;
33730 those that are added at delivery time (such as &'Envelope-To:'& and
33731 &'Return-Path:'&) cannot be removed by this means. If there is more than one
33732 header with the same name, they are all removed.
33734 The &%headers%& command in a system filter makes an immediate change to the set
33735 of header lines that was received with the message (with possible additions
33736 from ACL processing). Subsequent commands in the system filter operate on the
33737 modified set, which also forms the basis for subsequent message delivery.
33738 Unless further modified during routing or transporting, this set of headers is
33739 used for all recipients of the message.
33741 During routing and transporting, the variables that refer to the contents of
33742 header lines refer only to those lines that are in this set. Thus, header lines
33743 that are added by a system filter are visible to users' filter files and to all
33744 routers and transports. This contrasts with the manipulation of header lines by
33745 routers and transports, which is not immediate, but which instead is saved up
33746 until the message is actually being written (see section
33747 &<<SECTheadersaddrem>>&).
33749 If the message is not delivered at the first attempt, header lines that were
33750 added by the system filter are stored with the message, and so are still
33751 present at the next delivery attempt. Header lines that were removed are still
33752 present, but marked &"deleted"& so that they are not transported with the
33753 message. For this reason, it is usual to make the &%headers%& command
33754 conditional on &%first_delivery%& so that the set of header lines is not
33755 modified more than once.
33757 Because header modification in a system filter acts immediately, you have to
33758 use an indirect approach if you want to modify the contents of a header line.
33761 headers add "Old-Subject: $h_subject:"
33762 headers remove "Subject"
33763 headers add "Subject: new subject (was: $h_old-subject:)"
33764 headers remove "Old-Subject"
33769 .section "Setting an errors address in a system filter" "SECID217"
33770 .cindex "envelope sender"
33771 In a system filter, if a &%deliver%& command is followed by
33773 errors_to <some address>
33775 in order to change the envelope sender (and hence the error reporting) for that
33776 delivery, any address may be specified. (In a user filter, only the current
33777 user's address can be set.) For example, if some mail is being monitored, you
33780 unseen deliver monitor@spying.example errors_to root@local.example
33782 to take a copy which would not be sent back to the normal error reporting
33783 address if its delivery failed.
33787 .section "Per-address filtering" "SECTperaddfil"
33788 .vindex "&$domain$&"
33789 .vindex "&$local_part$&"
33790 In contrast to the system filter, which is run just once per message for each
33791 delivery attempt, it is also possible to set up a system-wide filtering
33792 operation that runs once for each recipient address. In this case, variables
33793 such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
33794 filter file could be made dependent on them. This is an example of a router
33795 which implements such a filter:
33800 domains = +local_domains
33801 file = /central/filters/$local_part
33806 The filter is run in a separate process under its own uid. Therefore, either
33807 &%check_local_user%& must be set (as above), in which case the filter is run as
33808 the local user, or the &%user%& option must be used to specify which user to
33809 use. If both are set, &%user%& overrides.
33811 Care should be taken to ensure that none of the commands in the filter file
33812 specify a significant delivery if the message is to go on to be delivered to
33813 its intended recipient. The router will not then claim to have dealt with the
33814 address, so it will be passed on to subsequent routers to be delivered in the
33816 .ecindex IIDsysfil1
33817 .ecindex IIDsysfil2
33818 .ecindex IIDsysfil3
33825 . ////////////////////////////////////////////////////////////////////////////
33826 . ////////////////////////////////////////////////////////////////////////////
33828 .chapter "Message processing" "CHAPmsgproc"
33829 .scindex IIDmesproc "message" "general processing"
33830 Exim performs various transformations on the sender and recipient addresses of
33831 all messages that it handles, and also on the messages' header lines. Some of
33832 these are optional and configurable, while others always take place. All of
33833 this processing, except rewriting as a result of routing, and the addition or
33834 removal of header lines while delivering, happens when a message is received,
33835 before it is placed on Exim's queue.
33837 Some of the automatic processing takes place by default only for
33838 &"locally-originated"& messages. This adjective is used to describe messages
33839 that are not received over TCP/IP, but instead are passed to an Exim process on
33840 its standard input. This includes the interactive &"local SMTP"& case that is
33841 set up by the &%-bs%& command line option.
33843 &*Note*&: Messages received over TCP/IP on the loopback interface (127.0.0.1
33844 or ::1) are not considered to be locally-originated. Exim does not treat the
33845 loopback interface specially in any way.
33847 If you want the loopback interface to be treated specially, you must ensure
33848 that there are appropriate entries in your ACLs.
33853 .section "Submission mode for non-local messages" "SECTsubmodnon"
33854 .cindex "message" "submission"
33855 .cindex "submission mode"
33856 Processing that happens automatically for locally-originated messages (unless
33857 &%suppress_local_fixups%& is set) can also be requested for messages that are
33858 received over TCP/IP. The term &"submission mode"& is used to describe this
33859 state. Submission mode is set by the modifier
33861 control = submission
33863 in a MAIL, RCPT, or pre-data ACL for an incoming message (see sections
33864 &<<SECTACLmodi>>& and &<<SECTcontrols>>&). This makes Exim treat the message as
33865 a local submission, and is normally used when the source of the message is
33866 known to be an MUA running on a client host (as opposed to an MTA). For
33867 example, to set submission mode for messages originating on the IPv4 loopback
33868 interface, you could include the following in the MAIL ACL:
33870 warn hosts = 127.0.0.1
33871 control = submission
33873 .cindex "&%sender_retain%& submission option"
33874 There are some options that can be used when setting submission mode. A slash
33875 is used to separate options. For example:
33877 control = submission/sender_retain
33879 Specifying &%sender_retain%& has the effect of setting &%local_sender_retain%&
33880 true and &%local_from_check%& false for the current incoming message. The first
33881 of these allows an existing &'Sender:'& header in the message to remain, and
33882 the second suppresses the check to ensure that &'From:'& matches the
33883 authenticated sender. With this setting, Exim still fixes up messages by adding
33884 &'Date:'& and &'Message-ID:'& header lines if they are missing, but makes no
33885 attempt to check sender authenticity in header lines.
33887 When &%sender_retain%& is not set, a submission mode setting may specify a
33888 domain to be used when generating a &'From:'& or &'Sender:'& header line. For
33891 control = submission/domain=some.domain
33893 The domain may be empty. How this value is used is described in sections
33894 &<<SECTthefrohea>>& and &<<SECTthesenhea>>&. There is also a &%name%& option
33895 that allows you to specify the user's full name for inclusion in a created
33896 &'Sender:'& or &'From:'& header line. For example:
33898 accept authenticated = *
33899 control = submission/domain=wonderland.example/\
33900 name=${lookup {$authenticated_id} \
33901 lsearch {/etc/exim/namelist}}
33903 Because the name may contain any characters, including slashes, the &%name%&
33904 option must be given last. The remainder of the string is used as the name. For
33905 the example above, if &_/etc/exim/namelist_& contains:
33907 bigegg: Humpty Dumpty
33909 then when the sender has authenticated as &'bigegg'&, the generated &'Sender:'&
33912 Sender: Humpty Dumpty <bigegg@wonderland.example>
33914 .cindex "return path" "in submission mode"
33915 By default, submission mode forces the return path to the same address as is
33916 used to create the &'Sender:'& header. However, if &%sender_retain%& is
33917 specified, the return path is also left unchanged.
33919 &*Note*&: The changes caused by submission mode take effect after the predata
33920 ACL. This means that any sender checks performed before the fix-ups use the
33921 untrusted sender address specified by the user, not the trusted sender address
33922 specified by submission mode. Although this might be slightly unexpected, it
33923 does mean that you can configure ACL checks to spot that a user is trying to
33924 spoof another's address.
33926 .section "Line endings" "SECTlineendings"
33927 .cindex "line endings"
33928 .cindex "carriage return"
33930 RFC 2821 specifies that CRLF (two characters: carriage-return, followed by
33931 linefeed) is the line ending for messages transmitted over the Internet using
33932 SMTP over TCP/IP. However, within individual operating systems, different
33933 conventions are used. For example, Unix-like systems use just LF, but others
33934 use CRLF or just CR.
33936 Exim was designed for Unix-like systems, and internally, it stores messages
33937 using the system's convention of a single LF as a line terminator. When
33938 receiving a message, all line endings are translated to this standard format.
33939 Originally, it was thought that programs that passed messages directly to an
33940 MTA within an operating system would use that system's convention. Experience
33941 has shown that this is not the case; for example, there are Unix applications
33942 that use CRLF in this circumstance. For this reason, and for compatibility with
33943 other MTAs, the way Exim handles line endings for all messages is now as
33947 LF not preceded by CR is treated as a line ending.
33949 CR is treated as a line ending; if it is immediately followed by LF, the LF
33952 The sequence &"CR, dot, CR"& does not terminate an incoming SMTP message,
33953 nor a local message in the state where a line containing only a dot is a
33956 If a bare CR is encountered within a header line, an extra space is added after
33957 the line terminator so as not to end the header line. The reasoning behind this
33958 is that bare CRs in header lines are most likely either to be mistakes, or
33959 people trying to play silly games.
33961 If the first header line received in a message ends with CRLF, a subsequent
33962 bare LF in a header line is treated in the same way as a bare CR in a header
33970 .section "Unqualified addresses" "SECID218"
33971 .cindex "unqualified addresses"
33972 .cindex "address" "qualification"
33973 By default, Exim expects every envelope address it receives from an external
33974 host to be fully qualified. Unqualified addresses cause negative responses to
33975 SMTP commands. However, because SMTP is used as a means of transporting
33976 messages from MUAs running on personal workstations, there is sometimes a
33977 requirement to accept unqualified addresses from specific hosts or IP networks.
33979 Exim has two options that separately control which hosts may send unqualified
33980 sender or recipient addresses in SMTP commands, namely
33981 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&. In both
33982 cases, if an unqualified address is accepted, it is qualified by adding the
33983 value of &%qualify_domain%& or &%qualify_recipient%&, as appropriate.
33985 .oindex "&%qualify_domain%&"
33986 .oindex "&%qualify_recipient%&"
33987 Unqualified addresses in header lines are automatically qualified for messages
33988 that are locally originated, unless the &%-bnq%& option is given on the command
33989 line. For messages received over SMTP, unqualified addresses in header lines
33990 are qualified only if unqualified addresses are permitted in SMTP commands. In
33991 other words, such qualification is also controlled by
33992 &%sender_unqualified_hosts%& and &%recipient_unqualified_hosts%&,
33997 .section "The UUCP From line" "SECID219"
33998 .cindex "&""From""& line"
33999 .cindex "UUCP" "&""From""& line"
34000 .cindex "sender" "address"
34001 .oindex "&%uucp_from_pattern%&"
34002 .oindex "&%uucp_from_sender%&"
34003 .cindex "envelope sender"
34004 .cindex "Sendmail compatibility" "&""From""& line"
34005 Messages that have come from UUCP (and some other applications) often begin
34006 with a line containing the envelope sender and a timestamp, following the word
34007 &"From"&. Examples of two common formats are:
34009 From a.oakley@berlin.mus Fri Jan 5 12:35 GMT 1996
34010 From f.butler@berlin.mus Fri, 7 Jan 97 14:00:00 GMT
34012 This line precedes the RFC 2822 header lines. For compatibility with Sendmail,
34013 Exim recognizes such lines at the start of messages that are submitted to it
34014 via the command line (that is, on the standard input). It does not recognize
34015 such lines in incoming SMTP messages, unless the sending host matches
34016 &%ignore_fromline_hosts%& or the &%-bs%& option was used for a local message
34017 and &%ignore_fromline_local%& is set. The recognition is controlled by a
34018 regular expression that is defined by the &%uucp_from_pattern%& option, whose
34019 default value matches the two common cases shown above and puts the address
34020 that follows &"From"& into &$1$&.
34022 .cindex "numerical variables (&$1$& &$2$& etc)" "in &""From ""& line handling"
34023 When the caller of Exim for a non-SMTP message that contains a &"From"& line is
34024 a trusted user, the message's sender address is constructed by expanding the
34025 contents of &%uucp_sender_address%&, whose default value is &"$1"&. This is
34026 then parsed as an RFC 2822 address. If there is no domain, the local part is
34027 qualified with &%qualify_domain%& unless it is the empty string. However, if
34028 the command line &%-f%& option is used, it overrides the &"From"& line.
34030 If the caller of Exim is not trusted, the &"From"& line is recognized, but the
34031 sender address is not changed. This is also the case for incoming SMTP messages
34032 that are permitted to contain &"From"& lines.
34034 Only one &"From"& line is recognized. If there is more than one, the second is
34035 treated as a data line that starts the body of the message, as it is not valid
34036 as a header line. This also happens if a &"From"& line is present in an
34037 incoming SMTP message from a source that is not permitted to send them.
34041 .section "Resent- header lines" "SECID220"
34042 .cindex "&%Resent-%& header lines"
34043 .cindex "header lines" "Resent-"
34044 RFC 2822 makes provision for sets of header lines starting with the string
34045 &`Resent-`& to be added to a message when it is resent by the original
34046 recipient to somebody else. These headers are &'Resent-Date:'&,
34047 &'Resent-From:'&, &'Resent-Sender:'&, &'Resent-To:'&, &'Resent-Cc:'&,
34048 &'Resent-Bcc:'& and &'Resent-Message-ID:'&. The RFC says:
34051 &'Resent fields are strictly informational. They MUST NOT be used in the normal
34052 processing of replies or other such automatic actions on messages.'&
34055 This leaves things a bit vague as far as other processing actions such as
34056 address rewriting are concerned. Exim treats &%Resent-%& header lines as
34060 A &'Resent-From:'& line that just contains the login id of the submitting user
34061 is automatically rewritten in the same way as &'From:'& (see below).
34063 If there's a rewriting rule for a particular header line, it is also applied to
34064 &%Resent-%& header lines of the same type. For example, a rule that rewrites
34065 &'From:'& also rewrites &'Resent-From:'&.
34067 For local messages, if &'Sender:'& is removed on input, &'Resent-Sender:'& is
34070 For a locally-submitted message,
34071 if there are any &%Resent-%& header lines but no &'Resent-Date:'&,
34072 &'Resent-From:'&, or &'Resent-Message-Id:'&, they are added as necessary. It is
34073 the contents of &'Resent-Message-Id:'& (rather than &'Message-Id:'&) which are
34074 included in log lines in this case.
34076 The logic for adding &'Sender:'& is duplicated for &'Resent-Sender:'& when any
34077 &%Resent-%& header lines are present.
34083 .section "The Auto-Submitted: header line" "SECID221"
34084 Whenever Exim generates an autoreply, a bounce, or a delay warning message, it
34085 includes the header line:
34087 Auto-Submitted: auto-replied
34090 .section "The Bcc: header line" "SECID222"
34091 .cindex "&'Bcc:'& header line"
34092 If Exim is called with the &%-t%& option, to take recipient addresses from a
34093 message's header, it removes any &'Bcc:'& header line that may exist (after
34094 extracting its addresses). If &%-t%& is not present on the command line, any
34095 existing &'Bcc:'& is not removed.
34098 .section "The Date: header line" "SECID223"
34099 .cindex "&'Date:'& header line"
34100 .cindex "header lines" "Date:"
34101 If a locally-generated or submission-mode message has no &'Date:'& header line,
34102 Exim adds one, using the current date and time, unless the
34103 &%suppress_local_fixups%& control has been specified.
34105 .section "The Delivery-date: header line" "SECID224"
34106 .cindex "&'Delivery-date:'& header line"
34107 .oindex "&%delivery_date_remove%&"
34108 &'Delivery-date:'& header lines are not part of the standard RFC 2822 header
34109 set. Exim can be configured to add them to the final delivery of messages. (See
34110 the generic &%delivery_date_add%& transport option.) They should not be present
34111 in messages in transit. If the &%delivery_date_remove%& configuration option is
34112 set (the default), Exim removes &'Delivery-date:'& header lines from incoming
34116 .section "The Envelope-to: header line" "SECID225"
34117 .cindex "&'Envelope-to:'& header line"
34118 .cindex "header lines" "Envelope-to:"
34119 .oindex "&%envelope_to_remove%&"
34120 &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
34121 Exim can be configured to add them to the final delivery of messages. (See the
34122 generic &%envelope_to_add%& transport option.) They should not be present in
34123 messages in transit. If the &%envelope_to_remove%& configuration option is set
34124 (the default), Exim removes &'Envelope-to:'& header lines from incoming
34128 .section "The From: header line" "SECTthefrohea"
34129 .cindex "&'From:'& header line"
34130 .cindex "header lines" "From:"
34131 .cindex "Sendmail compatibility" "&""From""& line"
34132 .cindex "message" "submission"
34133 .cindex "submission mode"
34134 If a submission-mode message does not contain a &'From:'& header line, Exim
34135 adds one if either of the following conditions is true:
34138 The envelope sender address is not empty (that is, this is not a bounce
34139 message). The added header line copies the envelope sender address.
34141 .vindex "&$authenticated_id$&"
34142 The SMTP session is authenticated and &$authenticated_id$& is not empty.
34144 .vindex "&$qualify_domain$&"
34145 If no domain is specified by the submission control, the local part is
34146 &$authenticated_id$& and the domain is &$qualify_domain$&.
34148 If a non-empty domain is specified by the submission control, the local
34149 part is &$authenticated_id$&, and the domain is the specified domain.
34151 If an empty domain is specified by the submission control,
34152 &$authenticated_id$& is assumed to be the complete address.
34156 A non-empty envelope sender takes precedence.
34158 If a locally-generated incoming message does not contain a &'From:'& header
34159 line, and the &%suppress_local_fixups%& control is not set, Exim adds one
34160 containing the sender's address. The calling user's login name and full name
34161 are used to construct the address, as described in section &<<SECTconstr>>&.
34162 They are obtained from the password data by calling &[getpwuid()]& (but see the
34163 &%unknown_login%& configuration option). The address is qualified with
34164 &%qualify_domain%&.
34166 For compatibility with Sendmail, if an incoming, non-SMTP message has a
34167 &'From:'& header line containing just the unqualified login name of the calling
34168 user, this is replaced by an address containing the user's login name and full
34169 name as described in section &<<SECTconstr>>&.
34172 .section "The Message-ID: header line" "SECID226"
34173 .cindex "&'Message-ID:'& header line"
34174 .cindex "header lines" "Message-ID:"
34175 .cindex "message" "submission"
34176 .oindex "&%message_id_header_text%&"
34177 If a locally-generated or submission-mode incoming message does not contain a
34178 &'Message-ID:'& or &'Resent-Message-ID:'& header line, and the
34179 &%suppress_local_fixups%& control is not set, Exim adds a suitable header line
34180 to the message. If there are any &'Resent-:'& headers in the message, it
34181 creates &'Resent-Message-ID:'&. The id is constructed from Exim's internal
34182 message id, preceded by the letter E to ensure it starts with a letter, and
34183 followed by @ and the primary host name. Additional information can be included
34184 in this header line by setting the &%message_id_header_text%& and/or
34185 &%message_id_header_domain%& options.
34188 .section "The Received: header line" "SECID227"
34189 .cindex "&'Received:'& header line"
34190 .cindex "header lines" "Received:"
34191 A &'Received:'& header line is added at the start of every message. The
34192 contents are defined by the &%received_header_text%& configuration option, and
34193 Exim automatically adds a semicolon and a timestamp to the configured string.
34195 The &'Received:'& header is generated as soon as the message's header lines
34196 have been received. At this stage, the timestamp in the &'Received:'& header
34197 line is the time that the message started to be received. This is the value
34198 that is seen by the DATA ACL and by the &[local_scan()]& function.
34200 Once a message is accepted, the timestamp in the &'Received:'& header line is
34201 changed to the time of acceptance, which is (apart from a small delay while the
34202 -H spool file is written) the earliest time at which delivery could start.
34205 .section "The References: header line" "SECID228"
34206 .cindex "&'References:'& header line"
34207 .cindex "header lines" "References:"
34208 Messages created by the &(autoreply)& transport include a &'References:'&
34209 header line. This is constructed according to the rules that are described in
34210 section 3.64 of RFC 2822 (which states that replies should contain such a
34211 header line), and section 3.14 of RFC 3834 (which states that automatic
34212 responses are not different in this respect). However, because some mail
34213 processing software does not cope well with very long header lines, no more
34214 than 12 message IDs are copied from the &'References:'& header line in the
34215 incoming message. If there are more than 12, the first one and then the final
34216 11 are copied, before adding the message ID of the incoming message.
34220 .section "The Return-path: header line" "SECID229"
34221 .cindex "&'Return-path:'& header line"
34222 .cindex "header lines" "Return-path:"
34223 .oindex "&%return_path_remove%&"
34224 &'Return-path:'& header lines are defined as something an MTA may insert when
34225 it does the final delivery of messages. (See the generic &%return_path_add%&
34226 transport option.) Therefore, they should not be present in messages in
34227 transit. If the &%return_path_remove%& configuration option is set (the
34228 default), Exim removes &'Return-path:'& header lines from incoming messages.
34232 .section "The Sender: header line" "SECTthesenhea"
34233 .cindex "&'Sender:'& header line"
34234 .cindex "message" "submission"
34235 .cindex "header lines" "Sender:"
34236 For a locally-originated message from an untrusted user, Exim may remove an
34237 existing &'Sender:'& header line, and it may add a new one. You can modify
34238 these actions by setting the &%local_sender_retain%& option true, the
34239 &%local_from_check%& option false, or by using the &%suppress_local_fixups%&
34242 When a local message is received from an untrusted user and
34243 &%local_from_check%& is true (the default), and the &%suppress_local_fixups%&
34244 control has not been set, a check is made to see if the address given in the
34245 &'From:'& header line is the correct (local) sender of the message. The address
34246 that is expected has the login name as the local part and the value of
34247 &%qualify_domain%& as the domain. Prefixes and suffixes for the local part can
34248 be permitted by setting &%local_from_prefix%& and &%local_from_suffix%&
34249 appropriately. If &'From:'& does not contain the correct sender, a &'Sender:'&
34250 line is added to the message.
34252 If you set &%local_from_check%& false, this checking does not occur. However,
34253 the removal of an existing &'Sender:'& line still happens, unless you also set
34254 &%local_sender_retain%& to be true. It is not possible to set both of these
34255 options true at the same time.
34257 .cindex "submission mode"
34258 By default, no processing of &'Sender:'& header lines is done for messages
34259 received over TCP/IP or for messages submitted by trusted users. However, when
34260 a message is received over TCP/IP in submission mode, and &%sender_retain%& is
34261 not specified on the submission control, the following processing takes place:
34263 .vindex "&$authenticated_id$&"
34264 First, any existing &'Sender:'& lines are removed. Then, if the SMTP session is
34265 authenticated, and &$authenticated_id$& is not empty, a sender address is
34266 created as follows:
34269 .vindex "&$qualify_domain$&"
34270 If no domain is specified by the submission control, the local part is
34271 &$authenticated_id$& and the domain is &$qualify_domain$&.
34273 If a non-empty domain is specified by the submission control, the local part
34274 is &$authenticated_id$&, and the domain is the specified domain.
34276 If an empty domain is specified by the submission control,
34277 &$authenticated_id$& is assumed to be the complete address.
34280 This address is compared with the address in the &'From:'& header line. If they
34281 are different, a &'Sender:'& header line containing the created address is
34282 added. Prefixes and suffixes for the local part in &'From:'& can be permitted
34283 by setting &%local_from_prefix%& and &%local_from_suffix%& appropriately.
34285 .cindex "return path" "created from &'Sender:'&"
34286 &*Note*&: Whenever a &'Sender:'& header line is created, the return path for
34287 the message (the envelope sender address) is changed to be the same address,
34288 except in the case of submission mode when &%sender_retain%& is specified.
34292 .section "Adding and removing header lines in routers and transports" &&&
34293 "SECTheadersaddrem"
34294 .cindex "header lines" "adding; in router or transport"
34295 .cindex "header lines" "removing; in router or transport"
34296 When a message is delivered, the addition and removal of header lines can be
34297 specified in a system filter, or on any of the routers and transports that
34298 process the message. Section &<<SECTaddremheasys>>& contains details about
34299 modifying headers in a system filter. Header lines can also be added in an ACL
34300 as a message is received (see section &<<SECTaddheadacl>>&).
34302 In contrast to what happens in a system filter, header modifications that are
34303 specified on routers and transports apply only to the particular recipient
34304 addresses that are being processed by those routers and transports. These
34305 changes do not actually take place until a copy of the message is being
34306 transported. Therefore, they do not affect the basic set of header lines, and
34307 they do not affect the values of the variables that refer to header lines.
34309 &*Note*&: In particular, this means that any expansions in the configuration of
34310 the transport cannot refer to the modified header lines, because such
34311 expansions all occur before the message is actually transported.
34313 For both routers and transports, the argument of a &%headers_add%&
34314 option must be in the form of one or more RFC 2822 header lines, separated by
34315 newlines (coded as &"\n"&). For example:
34317 headers_add = X-added-header: added by $primary_hostname\n\
34318 X-added-second: another added header line
34320 Exim does not check the syntax of these added header lines.
34322 Multiple &%headers_add%& options for a single router or transport can be
34323 specified; the values will append to a single list of header lines.
34324 Each header-line is separately expanded.
34326 The argument of a &%headers_remove%& option must consist of a colon-separated
34327 list of header names. This is confusing, because header names themselves are
34328 often terminated by colons. In this case, the colons are the list separators,
34329 not part of the names. For example:
34331 headers_remove = return-receipt-to:acknowledge-to
34334 Multiple &%headers_remove%& options for a single router or transport can be
34335 specified; the arguments will append to a single header-names list.
34336 Each item is separately expanded.
34337 Note that colons in complex expansions which are used to
34338 form all or part of a &%headers_remove%& list
34339 will act as list separators.
34341 When &%headers_add%& or &%headers_remove%& is specified on a router,
34342 items are expanded at routing time,
34343 and then associated with all addresses that are
34344 accepted by that router, and also with any new addresses that it generates. If
34345 an address passes through several routers as a result of aliasing or
34346 forwarding, the changes are cumulative.
34348 .oindex "&%unseen%&"
34349 However, this does not apply to multiple routers that result from the use of
34350 the &%unseen%& option. Any header modifications that were specified by the
34351 &"unseen"& router or its predecessors apply only to the &"unseen"& delivery.
34353 Addresses that end up with different &%headers_add%& or &%headers_remove%&
34354 settings cannot be delivered together in a batch, so a transport is always
34355 dealing with a set of addresses that have the same header-processing
34358 The transport starts by writing the original set of header lines that arrived
34359 with the message, possibly modified by the system filter. As it writes out
34360 these lines, it consults the list of header names that were attached to the
34361 recipient address(es) by &%headers_remove%& options in routers, and it also
34362 consults the transport's own &%headers_remove%& option. Header lines whose
34363 names are on either of these lists are not written out. If there are multiple
34364 instances of any listed header, they are all skipped.
34366 After the remaining original header lines have been written, new header
34367 lines that were specified by routers' &%headers_add%& options are written, in
34368 the order in which they were attached to the address. These are followed by any
34369 header lines specified by the transport's &%headers_add%& option.
34371 This way of handling header line modifications in routers and transports has
34372 the following consequences:
34375 The original set of header lines, possibly modified by the system filter,
34376 remains &"visible"&, in the sense that the &$header_$&&'xxx'& variables refer
34377 to it, at all times.
34379 Header lines that are added by a router's
34380 &%headers_add%& option are not accessible by means of the &$header_$&&'xxx'&
34381 expansion syntax in subsequent routers or the transport.
34383 Conversely, header lines that are specified for removal by &%headers_remove%&
34384 in a router remain visible to subsequent routers and the transport.
34386 Headers added to an address by &%headers_add%& in a router cannot be removed by
34387 a later router or by a transport.
34389 An added header can refer to the contents of an original header that is to be
34390 removed, even it has the same name as the added header. For example:
34392 headers_remove = subject
34393 headers_add = Subject: new subject (was: $h_subject:)
34397 &*Warning*&: The &%headers_add%& and &%headers_remove%& options cannot be used
34398 for a &(redirect)& router that has the &%one_time%& option set.
34404 .section "Constructed addresses" "SECTconstr"
34405 .cindex "address" "constructed"
34406 .cindex "constructed address"
34407 When Exim constructs a sender address for a locally-generated message, it uses
34410 <&'user name'&>&~&~<&'login'&&`@`&&'qualify_domain'&>
34414 Zaphod Beeblebrox <zaphod@end.univ.example>
34416 The user name is obtained from the &%-F%& command line option if set, or
34417 otherwise by looking up the calling user by &[getpwuid()]& and extracting the
34418 &"gecos"& field from the password entry. If the &"gecos"& field contains an
34419 ampersand character, this is replaced by the login name with the first letter
34420 upper cased, as is conventional in a number of operating systems. See the
34421 &%gecos_name%& option for a way to tailor the handling of the &"gecos"& field.
34422 The &%unknown_username%& option can be used to specify user names in cases when
34423 there is no password file entry.
34426 In all cases, the user name is made to conform to RFC 2822 by quoting all or
34427 parts of it if necessary. In addition, if it contains any non-printing
34428 characters, it is encoded as described in RFC 2047, which defines a way of
34429 including non-ASCII characters in header lines. The value of the
34430 &%headers_charset%& option specifies the name of the encoding that is used (the
34431 characters are assumed to be in this encoding). The setting of
34432 &%print_topbitchars%& controls whether characters with the top bit set (that
34433 is, with codes greater than 127) count as printing characters or not.
34437 .section "Case of local parts" "SECID230"
34438 .cindex "case of local parts"
34439 .cindex "local part" "case of"
34440 RFC 2822 states that the case of letters in the local parts of addresses cannot
34441 be assumed to be non-significant. Exim preserves the case of local parts of
34442 addresses, but by default it uses a lower-cased form when it is routing,
34443 because on most Unix systems, usernames are in lower case and case-insensitive
34444 routing is required. However, any particular router can be made to use the
34445 original case for local parts by setting the &%caseful_local_part%& generic
34448 .cindex "mixed-case login names"
34449 If you must have mixed-case user names on your system, the best way to proceed,
34450 assuming you want case-independent handling of incoming email, is to set up
34451 your first router to convert incoming local parts in your domains to the
34452 correct case by means of a file lookup. For example:
34456 domains = +local_domains
34457 data = ${lookup{$local_part}cdb\
34458 {/etc/usercased.cdb}{$value}fail}\
34461 For this router, the local part is forced to lower case by the default action
34462 (&%caseful_local_part%& is not set). The lower-cased local part is used to look
34463 up a new local part in the correct case. If you then set &%caseful_local_part%&
34464 on any subsequent routers which process your domains, they will operate on
34465 local parts with the correct case in a case-sensitive manner.
34469 .section "Dots in local parts" "SECID231"
34470 .cindex "dot" "in local part"
34471 .cindex "local part" "dots in"
34472 RFC 2822 forbids empty components in local parts. That is, an unquoted local
34473 part may not begin or end with a dot, nor have two consecutive dots in the
34474 middle. However, it seems that many MTAs do not enforce this, so Exim permits
34475 empty components for compatibility.
34479 .section "Rewriting addresses" "SECID232"
34480 .cindex "rewriting" "addresses"
34481 Rewriting of sender and recipient addresses, and addresses in headers, can
34482 happen automatically, or as the result of configuration options, as described
34483 in chapter &<<CHAPrewrite>>&. The headers that may be affected by this are
34484 &'Bcc:'&, &'Cc:'&, &'From:'&, &'Reply-To:'&, &'Sender:'&, and &'To:'&.
34486 Automatic rewriting includes qualification, as mentioned above. The other case
34487 in which it can happen is when an incomplete non-local domain is given. The
34488 routing process may cause this to be expanded into the full domain name. For
34489 example, a header such as
34493 might get rewritten as
34495 To: hare@teaparty.wonderland.fict.example
34497 Rewriting as a result of routing is the one kind of message processing that
34498 does not happen at input time, as it cannot be done until the address has
34501 Strictly, one should not do &'any'& deliveries of a message until all its
34502 addresses have been routed, in case any of the headers get changed as a
34503 result of routing. However, doing this in practice would hold up many
34504 deliveries for unreasonable amounts of time, just because one address could not
34505 immediately be routed. Exim therefore does not delay other deliveries when
34506 routing of one or more addresses is deferred.
34507 .ecindex IIDmesproc
34511 . ////////////////////////////////////////////////////////////////////////////
34512 . ////////////////////////////////////////////////////////////////////////////
34514 .chapter "SMTP processing" "CHAPSMTP"
34515 .scindex IIDsmtpproc1 "SMTP" "processing details"
34516 .scindex IIDsmtpproc2 "LMTP" "processing details"
34517 Exim supports a number of different ways of using the SMTP protocol, and its
34518 LMTP variant, which is an interactive protocol for transferring messages into a
34519 closed mail store application. This chapter contains details of how SMTP is
34520 processed. For incoming mail, the following are available:
34523 SMTP over TCP/IP (Exim daemon or &'inetd'&);
34525 SMTP over the standard input and output (the &%-bs%& option);
34527 Batched SMTP on the standard input (the &%-bS%& option).
34530 For mail delivery, the following are available:
34533 SMTP over TCP/IP (the &(smtp)& transport);
34535 LMTP over TCP/IP (the &(smtp)& transport with the &%protocol%& option set to
34538 LMTP over a pipe to a process running in the local host (the &(lmtp)&
34541 Batched SMTP to a file or pipe (the &(appendfile)& and &(pipe)& transports with
34542 the &%use_bsmtp%& option set).
34545 &'Batched SMTP'& is the name for a process in which batches of messages are
34546 stored in or read from files (or pipes), in a format in which SMTP commands are
34547 used to contain the envelope information.
34551 .section "Outgoing SMTP and LMTP over TCP/IP" "SECToutSMTPTCP"
34552 .cindex "SMTP" "outgoing over TCP/IP"
34553 .cindex "outgoing SMTP over TCP/IP"
34554 .cindex "LMTP" "over TCP/IP"
34555 .cindex "outgoing LMTP over TCP/IP"
34558 .cindex "SIZE option on MAIL command"
34559 Outgoing SMTP and LMTP over TCP/IP is implemented by the &(smtp)& transport.
34560 The &%protocol%& option selects which protocol is to be used, but the actual
34561 processing is the same in both cases.
34563 If, in response to its EHLO command, Exim is told that the SIZE
34564 parameter is supported, it adds SIZE=<&'n'&> to each subsequent MAIL
34565 command. The value of <&'n'&> is the message size plus the value of the
34566 &%size_addition%& option (default 1024) to allow for additions to the message
34567 such as per-transport header lines, or changes made in a
34568 .cindex "transport" "filter"
34569 .cindex "filter" "transport filter"
34570 transport filter. If &%size_addition%& is set negative, the use of SIZE is
34573 If the remote server advertises support for PIPELINING, Exim uses the
34574 pipelining extension to SMTP (RFC 2197) to reduce the number of TCP/IP packets
34575 required for the transaction.
34577 If the remote server advertises support for the STARTTLS command, and Exim
34578 was built to support TLS encryption, it tries to start a TLS session unless the
34579 server matches &%hosts_avoid_tls%&. See chapter &<<CHAPTLS>>& for more details.
34580 Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport
34581 is called for verification.
34583 If the remote server advertises support for the AUTH command, Exim scans
34584 the authenticators configuration for any suitable client settings, as described
34585 in chapter &<<CHAPSMTPAUTH>>&.
34587 .cindex "carriage return"
34589 Responses from the remote host are supposed to be terminated by CR followed by
34590 LF. However, there are known to be hosts that do not send CR characters, so in
34591 order to be able to interwork with such hosts, Exim treats LF on its own as a
34594 If a message contains a number of different addresses, all those with the same
34595 characteristics (for example, the same envelope sender) that resolve to the
34596 same set of hosts, in the same order, are sent in a single SMTP transaction,
34597 even if they are for different domains, unless there are more than the setting
34598 of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case
34599 they are split into groups containing no more than &%max_rcpt%&s addresses
34600 each. If &%remote_max_parallel%& is greater than one, such groups may be sent
34601 in parallel sessions. The order of hosts with identical MX values is not
34602 significant when checking whether addresses can be batched in this way.
34604 When the &(smtp)& transport suffers a temporary failure that is not
34605 message-related, Exim updates its transport-specific database, which contains
34606 records indexed by host name that remember which messages are waiting for each
34607 particular host. It also updates the retry database with new retry times.
34609 .cindex "hints database" "retry keys"
34610 Exim's retry hints are based on host name plus IP address, so if one address of
34611 a multi-homed host is broken, it will soon be skipped most of the time.
34612 See the next section for more detail about error handling.
34614 .cindex "SMTP" "passed connection"
34615 .cindex "SMTP" "batching over TCP/IP"
34616 When a message is successfully delivered over a TCP/IP SMTP connection, Exim
34617 looks in the hints database for the transport to see if there are any queued
34618 messages waiting for the host to which it is connected. If it finds one, it
34619 creates a new Exim process using the &%-MC%& option (which can only be used by
34620 a process running as root or the Exim user) and passes the TCP/IP socket to it
34621 so that it can deliver another message using the same socket. The new process
34622 does only those deliveries that are routed to the connected host, and may in
34623 turn pass the socket on to a third process, and so on.
34625 The &%connection_max_messages%& option of the &(smtp)& transport can be used to
34626 limit the number of messages sent down a single TCP/IP connection.
34628 .cindex "asterisk" "after IP address"
34629 The second and subsequent messages delivered down an existing connection are
34630 identified in the main log by the addition of an asterisk after the closing
34631 square bracket of the IP address.
34636 .section "Errors in outgoing SMTP" "SECToutSMTPerr"
34637 .cindex "error" "in outgoing SMTP"
34638 .cindex "SMTP" "errors in outgoing"
34639 .cindex "host" "error"
34640 Three different kinds of error are recognized for outgoing SMTP: host errors,
34641 message errors, and recipient errors.
34644 .vitem "&*Host errors*&"
34645 A host error is not associated with a particular message or with a
34646 particular recipient of a message. The host errors are:
34649 Connection refused or timed out,
34651 Any error response code on connection,
34653 Any error response code to EHLO or HELO,
34655 Loss of connection at any time, except after &"."&,
34657 I/O errors at any time,
34659 Timeouts during the session, other than in response to MAIL, RCPT or
34660 the &"."& at the end of the data.
34663 For a host error, a permanent error response on connection, or in response to
34664 EHLO, causes all addresses routed to the host to be failed. Any other host
34665 error causes all addresses to be deferred, and retry data to be created for the
34666 host. It is not tried again, for any message, until its retry time arrives. If
34667 the current set of addresses are not all delivered in this run (to some
34668 alternative host), the message is added to the list of those waiting for this
34669 host, so if it is still undelivered when a subsequent successful delivery is
34670 made to the host, it will be sent down the same SMTP connection.
34672 .vitem "&*Message errors*&"
34673 .cindex "message" "error"
34674 A message error is associated with a particular message when sent to a
34675 particular host, but not with a particular recipient of the message. The
34676 message errors are:
34679 Any error response code to MAIL, DATA, or the &"."& that terminates
34682 Timeout after MAIL,
34684 Timeout or loss of connection after the &"."& that terminates the data. A
34685 timeout after the DATA command itself is treated as a host error, as is loss of
34686 connection at any other time.
34689 For a message error, a permanent error response (5&'xx'&) causes all addresses
34690 to be failed, and a delivery error report to be returned to the sender. A
34691 temporary error response (4&'xx'&), or one of the timeouts, causes all
34692 addresses to be deferred. Retry data is not created for the host, but instead,
34693 a retry record for the combination of host plus message id is created. The
34694 message is not added to the list of those waiting for this host. This ensures
34695 that the failing message will not be sent to this host again until the retry
34696 time arrives. However, other messages that are routed to the host are not
34697 affected, so if it is some property of the message that is causing the error,
34698 it will not stop the delivery of other mail.
34700 If the remote host specified support for the SIZE parameter in its response
34701 to EHLO, Exim adds SIZE=&'nnn'& to the MAIL command, so an
34702 over-large message will cause a message error because the error arrives as a
34705 .vitem "&*Recipient errors*&"
34706 .cindex "recipient" "error"
34707 A recipient error is associated with a particular recipient of a message. The
34708 recipient errors are:
34711 Any error response to RCPT,
34713 Timeout after RCPT.
34716 For a recipient error, a permanent error response (5&'xx'&) causes the
34717 recipient address to be failed, and a bounce message to be returned to the
34718 sender. A temporary error response (4&'xx'&) or a timeout causes the failing
34719 address to be deferred, and routing retry data to be created for it. This is
34720 used to delay processing of the address in subsequent queue runs, until its
34721 routing retry time arrives. This applies to all messages, but because it
34722 operates only in queue runs, one attempt will be made to deliver a new message
34723 to the failing address before the delay starts to operate. This ensures that,
34724 if the failure is really related to the message rather than the recipient
34725 (&"message too big for this recipient"& is a possible example), other messages
34726 have a chance of getting delivered. If a delivery to the address does succeed,
34727 the retry information gets cleared, so all stuck messages get tried again, and
34728 the retry clock is reset.
34730 The message is not added to the list of those waiting for this host. Use of the
34731 host for other messages is unaffected, and except in the case of a timeout,
34732 other recipients are processed independently, and may be successfully delivered
34733 in the current SMTP session. After a timeout it is of course impossible to
34734 proceed with the session, so all addresses get deferred. However, those other
34735 than the one that failed do not suffer any subsequent retry delays. Therefore,
34736 if one recipient is causing trouble, the others have a chance of getting
34737 through when a subsequent delivery attempt occurs before the failing
34738 recipient's retry time.
34741 In all cases, if there are other hosts (or IP addresses) available for the
34742 current set of addresses (for example, from multiple MX records), they are
34743 tried in this run for any undelivered addresses, subject of course to their
34744 own retry data. In other words, recipient error retry data does not take effect
34745 until the next delivery attempt.
34747 Some hosts have been observed to give temporary error responses to every
34748 MAIL command at certain times (&"insufficient space"& has been seen). It
34749 would be nice if such circumstances could be recognized, and defer data for the
34750 host itself created, but this is not possible within the current Exim design.
34751 What actually happens is that retry data for every (host, message) combination
34754 The reason that timeouts after MAIL and RCPT are treated specially is that
34755 these can sometimes arise as a result of the remote host's verification
34756 procedures. Exim makes this assumption, and treats them as if a temporary error
34757 response had been received. A timeout after &"."& is treated specially because
34758 it is known that some broken implementations fail to recognize the end of the
34759 message if the last character of the last line is a binary zero. Thus, it is
34760 helpful to treat this case as a message error.
34762 Timeouts at other times are treated as host errors, assuming a problem with the
34763 host, or the connection to it. If a timeout after MAIL, RCPT,
34764 or &"."& is really a connection problem, the assumption is that at the next try
34765 the timeout is likely to occur at some other point in the dialogue, causing it
34766 then to be treated as a host error.
34768 There is experimental evidence that some MTAs drop the connection after the
34769 terminating &"."& if they do not like the contents of the message for some
34770 reason, in contravention of the RFC, which indicates that a 5&'xx'& response
34771 should be given. That is why Exim treats this case as a message rather than a
34772 host error, in order not to delay other messages to the same host.
34777 .section "Incoming SMTP messages over TCP/IP" "SECID233"
34778 .cindex "SMTP" "incoming over TCP/IP"
34779 .cindex "incoming SMTP over TCP/IP"
34782 Incoming SMTP messages can be accepted in one of two ways: by running a
34783 listening daemon, or by using &'inetd'&. In the latter case, the entry in
34784 &_/etc/inetd.conf_& should be like this:
34786 smtp stream tcp nowait exim /opt/exim/bin/exim in.exim -bs
34788 Exim distinguishes between this case and the case of a locally running user
34789 agent using the &%-bs%& option by checking whether or not the standard input is
34790 a socket. When it is, either the port must be privileged (less than 1024), or
34791 the caller must be root or the Exim user. If any other user passes a socket
34792 with an unprivileged port number, Exim prints a message on the standard error
34793 stream and exits with an error code.
34795 By default, Exim does not make a log entry when a remote host connects or
34796 disconnects (either via the daemon or &'inetd'&), unless the disconnection is
34797 unexpected. It can be made to write such log entries by setting the
34798 &%smtp_connection%& log selector.
34800 .cindex "carriage return"
34802 Commands from the remote host are supposed to be terminated by CR followed by
34803 LF. However, there are known to be hosts that do not send CR characters. In
34804 order to be able to interwork with such hosts, Exim treats LF on its own as a
34806 Furthermore, because common code is used for receiving messages from all
34807 sources, a CR on its own is also interpreted as a line terminator. However, the
34808 sequence &"CR, dot, CR"& does not terminate incoming SMTP data.
34810 .cindex "EHLO" "invalid data"
34811 .cindex "HELO" "invalid data"
34812 One area that sometimes gives rise to problems concerns the EHLO or
34813 HELO commands. Some clients send syntactically invalid versions of these
34814 commands, which Exim rejects by default. (This is nothing to do with verifying
34815 the data that is sent, so &%helo_verify_hosts%& is not relevant.) You can tell
34816 Exim not to apply a syntax check by setting &%helo_accept_junk_hosts%& to
34817 match the broken hosts that send invalid commands.
34819 .cindex "SIZE option on MAIL command"
34820 .cindex "MAIL" "SIZE option"
34821 The amount of disk space available is checked whenever SIZE is received on
34822 a MAIL command, independently of whether &%message_size_limit%& or
34823 &%check_spool_space%& is configured, unless &%smtp_check_spool_space%& is set
34824 false. A temporary error is given if there is not enough space. If
34825 &%check_spool_space%& is set, the check is for that amount of space plus the
34826 value given with SIZE, that is, it checks that the addition of the incoming
34827 message will not reduce the space below the threshold.
34829 When a message is successfully received, Exim includes the local message id in
34830 its response to the final &"."& that terminates the data. If the remote host
34831 logs this text it can help with tracing what has happened to a message.
34833 The Exim daemon can limit the number of simultaneous incoming connections it is
34834 prepared to handle (see the &%smtp_accept_max%& option). It can also limit the
34835 number of simultaneous incoming connections from a single remote host (see the
34836 &%smtp_accept_max_per_host%& option). Additional connection attempts are
34837 rejected using the SMTP temporary error code 421.
34839 The Exim daemon does not rely on the SIGCHLD signal to detect when a
34840 subprocess has finished, as this can get lost at busy times. Instead, it looks
34841 for completed subprocesses every time it wakes up. Provided there are other
34842 things happening (new incoming calls, starts of queue runs), completed
34843 processes will be noticed and tidied away. On very quiet systems you may
34844 sometimes see a &"defunct"& Exim process hanging about. This is not a problem;
34845 it will be noticed when the daemon next wakes up.
34847 When running as a daemon, Exim can reserve some SMTP slots for specific hosts,
34848 and can also be set up to reject SMTP calls from non-reserved hosts at times of
34849 high system load &-- for details see the &%smtp_accept_reserve%&,
34850 &%smtp_load_reserve%&, and &%smtp_reserve_hosts%& options. The load check
34851 applies in both the daemon and &'inetd'& cases.
34853 Exim normally starts a delivery process for each message received, though this
34854 can be varied by means of the &%-odq%& command line option and the
34855 &%queue_only%&, &%queue_only_file%&, and &%queue_only_load%& options. The
34856 number of simultaneously running delivery processes started in this way from
34857 SMTP input can be limited by the &%smtp_accept_queue%& and
34858 &%smtp_accept_queue_per_connection%& options. When either limit is reached,
34859 subsequently received messages are just put on the input queue without starting
34860 a delivery process.
34862 The controls that involve counts of incoming SMTP calls (&%smtp_accept_max%&,
34863 &%smtp_accept_queue%&, &%smtp_accept_reserve%&) are not available when Exim is
34864 started up from the &'inetd'& daemon, because in that case each connection is
34865 handled by an entirely independent Exim process. Control by load average is,
34866 however, available with &'inetd'&.
34868 Exim can be configured to verify addresses in incoming SMTP commands as they
34869 are received. See chapter &<<CHAPACL>>& for details. It can also be configured
34870 to rewrite addresses at this time &-- before any syntax checking is done. See
34871 section &<<SECTrewriteS>>&.
34873 Exim can also be configured to limit the rate at which a client host submits
34874 MAIL and RCPT commands in a single SMTP session. See the
34875 &%smtp_ratelimit_hosts%& option.
34879 .section "Unrecognized SMTP commands" "SECID234"
34880 .cindex "SMTP" "unrecognized commands"
34881 If Exim receives more than &%smtp_max_unknown_commands%& unrecognized SMTP
34882 commands during a single SMTP connection, it drops the connection after sending
34883 the error response to the last command. The default value for
34884 &%smtp_max_unknown_commands%& is 3. This is a defence against some kinds of
34885 abuse that subvert web servers into making connections to SMTP ports; in these
34886 circumstances, a number of non-SMTP lines are sent first.
34889 .section "Syntax and protocol errors in SMTP commands" "SECID235"
34890 .cindex "SMTP" "syntax errors"
34891 .cindex "SMTP" "protocol errors"
34892 A syntax error is detected if an SMTP command is recognized, but there is
34893 something syntactically wrong with its data, for example, a malformed email
34894 address in a RCPT command. Protocol errors include invalid command
34895 sequencing such as RCPT before MAIL. If Exim receives more than
34896 &%smtp_max_synprot_errors%& such commands during a single SMTP connection, it
34897 drops the connection after sending the error response to the last command. The
34898 default value for &%smtp_max_synprot_errors%& is 3. This is a defence against
34899 broken clients that loop sending bad commands (yes, it has been seen).
34903 .section "Use of non-mail SMTP commands" "SECID236"
34904 .cindex "SMTP" "non-mail commands"
34905 The &"non-mail"& SMTP commands are those other than MAIL, RCPT, and
34906 DATA. Exim counts such commands, and drops the connection if there are too
34907 many of them in a single SMTP session. This action catches some
34908 denial-of-service attempts and things like repeated failing AUTHs, or a mad
34909 client looping sending EHLO. The global option &%smtp_accept_max_nonmail%&
34910 defines what &"too many"& means. Its default value is 10.
34912 When a new message is expected, one occurrence of RSET is not counted. This
34913 allows a client to send one RSET between messages (this is not necessary,
34914 but some clients do it). Exim also allows one uncounted occurrence of HELO
34915 or EHLO, and one occurrence of STARTTLS between messages. After
34916 starting up a TLS session, another EHLO is expected, and so it too is not
34919 The first occurrence of AUTH in a connection, or immediately following
34920 STARTTLS is also not counted. Otherwise, all commands other than MAIL,
34921 RCPT, DATA, and QUIT are counted.
34923 You can control which hosts are subject to the limit set by
34924 &%smtp_accept_max_nonmail%& by setting
34925 &%smtp_accept_max_nonmail_hosts%&. The default value is &`*`&, which makes
34926 the limit apply to all hosts. This option means that you can exclude any
34927 specific badly-behaved hosts that you have to live with.
34932 .section "The VRFY and EXPN commands" "SECID237"
34933 When Exim receives a VRFY or EXPN command on a TCP/IP connection, it
34934 runs the ACL specified by &%acl_smtp_vrfy%& or &%acl_smtp_expn%& (as
34935 appropriate) in order to decide whether the command should be accepted or not.
34937 .cindex "VRFY" "processing"
34938 When no ACL is defined for VRFY, or if it rejects without
34939 setting an explicit response code, the command is accepted
34940 (with a 252 SMTP response code)
34941 in order to support awkward clients that do a VRFY before every RCPT.
34942 When VRFY is accepted, it runs exactly the same code as when Exim is
34943 called with the &%-bv%& option, and returns 250/451/550
34944 SMTP response codes.
34946 .cindex "EXPN" "processing"
34947 If no ACL for EXPN is defined, the command is rejected.
34948 When EXPN is accepted, a single-level expansion of the address is done.
34949 EXPN is treated as an &"address test"& (similar to the &%-bt%& option) rather
34950 than a verification (the &%-bv%& option). If an unqualified local part is given
34951 as the argument to EXPN, it is qualified with &%qualify_domain%&. Rejections
34952 of VRFY and EXPN commands are logged on the main and reject logs, and
34953 VRFY verification failures are logged on the main log for consistency with
34958 .section "The ETRN command" "SECTETRN"
34959 .cindex "ETRN" "processing"
34960 RFC 1985 describes an SMTP command called ETRN that is designed to
34961 overcome the security problems of the TURN command (which has fallen into
34962 disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs
34963 the ACL specified by &%acl_smtp_etrn%& in order to decide whether the command
34964 should be accepted or not. If no ACL is defined, the command is rejected.
34966 The ETRN command is concerned with &"releasing"& messages that are awaiting
34967 delivery to certain hosts. As Exim does not organize its message queue by host,
34968 the only form of ETRN that is supported by default is the one where the
34969 text starts with the &"#"& prefix, in which case the remainder of the text is
34970 specific to the SMTP server. A valid ETRN command causes a run of Exim with
34971 the &%-R%& option to happen, with the remainder of the ETRN text as its
34972 argument. For example,
34980 which causes a delivery attempt on all messages with undelivered addresses
34981 containing the text &"brigadoon"&. When &%smtp_etrn_serialize%& is set (the
34982 default), Exim prevents the simultaneous execution of more than one queue run
34983 for the same argument string as a result of an ETRN command. This stops
34984 a misbehaving client from starting more than one queue runner at once.
34986 .cindex "hints database" "ETRN serialization"
34987 Exim implements the serialization by means of a hints database in which a
34988 record is written whenever a process is started by ETRN, and deleted when
34989 the process completes. However, Exim does not keep the SMTP session waiting for
34990 the ETRN process to complete. Once ETRN is accepted, the client is sent
34991 a &"success"& return code. Obviously there is scope for hints records to get
34992 left lying around if there is a system or program crash. To guard against this,
34993 Exim ignores any records that are more than six hours old.
34995 .oindex "&%smtp_etrn_command%&"
34996 For more control over what ETRN does, the &%smtp_etrn_command%& option can
34997 used. This specifies a command that is run whenever ETRN is received,
34998 whatever the form of its argument. For
35001 smtp_etrn_command = /etc/etrn_command $domain \
35002 $sender_host_address
35004 .vindex "&$domain$&"
35005 The string is split up into arguments which are independently expanded. The
35006 expansion variable &$domain$& is set to the argument of the ETRN command,
35007 and no syntax checking is done on the contents of this argument. Exim does not
35008 wait for the command to complete, so its status code is not checked. Exim runs
35009 under its own uid and gid when receiving incoming SMTP, so it is not possible
35010 for it to change them before running the command.
35014 .section "Incoming local SMTP" "SECID238"
35015 .cindex "SMTP" "local incoming"
35016 Some user agents use SMTP to pass messages to their local MTA using the
35017 standard input and output, as opposed to passing the envelope on the command
35018 line and writing the message to the standard input. This is supported by the
35019 &%-bs%& option. This form of SMTP is handled in the same way as incoming
35020 messages over TCP/IP (including the use of ACLs), except that the envelope
35021 sender given in a MAIL command is ignored unless the caller is trusted. In
35022 an ACL you can detect this form of SMTP input by testing for an empty host
35023 identification. It is common to have this as the first line in the ACL that
35024 runs for RCPT commands:
35028 This accepts SMTP messages from local processes without doing any other tests.
35032 .section "Outgoing batched SMTP" "SECTbatchSMTP"
35033 .cindex "SMTP" "batched outgoing"
35034 .cindex "batched SMTP output"
35035 Both the &(appendfile)& and &(pipe)& transports can be used for handling
35036 batched SMTP. Each has an option called &%use_bsmtp%& which causes messages to
35037 be output in BSMTP format. No SMTP responses are possible for this form of
35038 delivery. All it is doing is using SMTP commands as a way of transmitting the
35039 envelope along with the message.
35041 The message is written to the file or pipe preceded by the SMTP commands
35042 MAIL and RCPT, and followed by a line containing a single dot. Lines in
35043 the message that start with a dot have an extra dot added. The SMTP command
35044 HELO is not normally used. If it is required, the &%message_prefix%& option
35045 can be used to specify it.
35047 Because &(appendfile)& and &(pipe)& are both local transports, they accept only
35048 one recipient address at a time by default. However, you can arrange for them
35049 to handle several addresses at once by setting the &%batch_max%& option. When
35050 this is done for BSMTP, messages may contain multiple RCPT commands. See
35051 chapter &<<CHAPbatching>>& for more details.
35054 When one or more addresses are routed to a BSMTP transport by a router that
35055 sets up a host list, the name of the first host on the list is available to the
35056 transport in the variable &$host$&. Here is an example of such a transport and
35061 driver = manualroute
35062 transport = smtp_appendfile
35063 route_list = domain.example batch.host.example
35067 driver = appendfile
35068 directory = /var/bsmtp/$host
35073 This causes messages addressed to &'domain.example'& to be written in BSMTP
35074 format to &_/var/bsmtp/batch.host.example_&, with only a single copy of each
35075 message (unless there are more than 1000 recipients).
35079 .section "Incoming batched SMTP" "SECTincomingbatchedSMTP"
35080 .cindex "SMTP" "batched incoming"
35081 .cindex "batched SMTP input"
35082 The &%-bS%& command line option causes Exim to accept one or more messages by
35083 reading SMTP on the standard input, but to generate no responses. If the caller
35084 is trusted, the senders in the MAIL commands are believed; otherwise the
35085 sender is always the caller of Exim. Unqualified senders and receivers are not
35086 rejected (there seems little point) but instead just get qualified. HELO
35087 and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act
35088 as NOOP; QUIT quits.
35090 Minimal policy checking is done for BSMTP input. Only the non-SMTP
35091 ACL is run in the same way as for non-SMTP local input.
35093 If an error is detected while reading a message, including a missing &"."& at
35094 the end, Exim gives up immediately. It writes details of the error to the
35095 standard output in a stylized way that the calling program should be able to
35096 make some use of automatically, for example:
35098 554 Unexpected end of file
35099 Transaction started in line 10
35100 Error detected in line 14
35102 It writes a more verbose version, for human consumption, to the standard error
35105 An error was detected while processing a file of BSMTP input.
35106 The error message was:
35108 501 '>' missing at end of address
35110 The SMTP transaction started in line 10.
35111 The error was detected in line 12.
35112 The SMTP command at fault was:
35114 rcpt to:<malformed@in.com.plete
35116 1 previous message was successfully processed.
35117 The rest of the batch was abandoned.
35119 The return code from Exim is zero only if there were no errors. It is 1 if some
35120 messages were accepted before an error was detected, and 2 if no messages were
35122 .ecindex IIDsmtpproc1
35123 .ecindex IIDsmtpproc2
35127 . ////////////////////////////////////////////////////////////////////////////
35128 . ////////////////////////////////////////////////////////////////////////////
35130 .chapter "Customizing bounce and warning messages" "CHAPemsgcust" &&&
35131 "Customizing messages"
35132 When a message fails to be delivered, or remains on the queue for more than a
35133 configured amount of time, Exim sends a message to the original sender, or
35134 to an alternative configured address. The text of these messages is built into
35135 the code of Exim, but it is possible to change it, either by adding a single
35136 string, or by replacing each of the paragraphs by text supplied in a file.
35138 The &'From:'& and &'To:'& header lines are automatically generated; you can
35139 cause a &'Reply-To:'& line to be added by setting the &%errors_reply_to%&
35140 option. Exim also adds the line
35142 Auto-Submitted: auto-generated
35144 to all warning and bounce messages,
35147 .section "Customizing bounce messages" "SECID239"
35148 .cindex "customizing" "bounce message"
35149 .cindex "bounce message" "customizing"
35150 If &%bounce_message_text%& is set, its contents are included in the default
35151 message immediately after &"This message was created automatically by mail
35152 delivery software."& The string is not expanded. It is not used if
35153 &%bounce_message_file%& is set.
35155 When &%bounce_message_file%& is set, it must point to a template file for
35156 constructing error messages. The file consists of a series of text items,
35157 separated by lines consisting of exactly four asterisks. If the file cannot be
35158 opened, default text is used and a message is written to the main and panic
35159 logs. If any text item in the file is empty, default text is used for that
35162 .vindex "&$bounce_recipient$&"
35163 .vindex "&$bounce_return_size_limit$&"
35164 Each item of text that is read from the file is expanded, and there are two
35165 expansion variables which can be of use here: &$bounce_recipient$& is set to
35166 the recipient of an error message while it is being created, and
35167 &$bounce_return_size_limit$& contains the value of the &%return_size_limit%&
35168 option, rounded to a whole number.
35170 The items must appear in the file in the following order:
35173 The first item is included in the headers, and should include at least a
35174 &'Subject:'& header. Exim does not check the syntax of these headers.
35176 The second item forms the start of the error message. After it, Exim lists the
35177 failing addresses with their error messages.
35179 The third item is used to introduce any text from pipe transports that is to be
35180 returned to the sender. It is omitted if there is no such text.
35182 The fourth, fifth and sixth items will be ignored and may be empty.
35183 The fields exist for back-compatibility
35186 The default state (&%bounce_message_file%& unset) is equivalent to the
35187 following file, in which the sixth item is empty. The &'Subject:'& and some
35188 other lines have been split in order to fit them on the page:
35190 Subject: Mail delivery failed
35191 ${if eq{$sender_address}{$bounce_recipient}
35192 {: returning message to sender}}
35194 This message was created automatically by mail delivery software.
35196 A message ${if eq{$sender_address}{$bounce_recipient}
35197 {that you sent }{sent by
35201 }}could not be delivered to all of its recipients.
35202 This is a permanent error. The following address(es) failed:
35204 The following text was generated during the delivery attempt(s):
35206 ------ This is a copy of the message, including all the headers.
35209 ------ The body of the message is $message_size characters long;
35211 ------ $bounce_return_size_limit or so are included here.
35214 .section "Customizing warning messages" "SECTcustwarn"
35215 .cindex "customizing" "warning message"
35216 .cindex "warning of delay" "customizing the message"
35217 The option &%warn_message_file%& can be pointed at a template file for use when
35218 warnings about message delays are created. In this case there are only three
35222 The first item is included in the headers, and should include at least a
35223 &'Subject:'& header. Exim does not check the syntax of these headers.
35225 The second item forms the start of the warning message. After it, Exim lists
35226 the delayed addresses.
35228 The third item then ends the message.
35231 The default state is equivalent to the following file, except that some lines
35232 have been split here, in order to fit them on the page:
35234 Subject: Warning: message $message_exim_id delayed
35235 $warn_message_delay
35237 This message was created automatically by mail delivery software.
35239 A message ${if eq{$sender_address}{$warn_message_recipients}
35240 {that you sent }{sent by
35244 }}has not been delivered to all of its recipients after
35245 more than $warn_message_delay on the queue on $primary_hostname.
35247 The message identifier is: $message_exim_id
35248 The subject of the message is: $h_subject
35249 The date of the message is: $h_date
35251 The following address(es) have not yet been delivered:
35253 No action is required on your part. Delivery attempts will
35254 continue for some time, and this warning may be repeated at
35255 intervals if the message remains undelivered. Eventually the
35256 mail delivery software will give up, and when that happens,
35257 the message will be returned to you.
35259 .vindex "&$warn_message_delay$&"
35260 .vindex "&$warn_message_recipients$&"
35261 However, in the default state the subject and date lines are omitted if no
35262 appropriate headers exist. During the expansion of this file,
35263 &$warn_message_delay$& is set to the delay time in one of the forms &"<&'n'&>
35264 minutes"& or &"<&'n'&> hours"&, and &$warn_message_recipients$& contains a list
35265 of recipients for the warning message. There may be more than one if there are
35266 multiple addresses with different &%errors_to%& settings on the routers that
35272 . ////////////////////////////////////////////////////////////////////////////
35273 . ////////////////////////////////////////////////////////////////////////////
35275 .chapter "Some common configuration settings" "CHAPcomconreq"
35276 This chapter discusses some configuration settings that seem to be fairly
35277 common. More examples and discussion can be found in the Exim book.
35281 .section "Sending mail to a smart host" "SECID240"
35282 .cindex "smart host" "example router"
35283 If you want to send all mail for non-local domains to a &"smart host"&, you
35284 should replace the default &(dnslookup)& router with a router which does the
35285 routing explicitly:
35287 send_to_smart_host:
35288 driver = manualroute
35289 route_list = !+local_domains smart.host.name
35290 transport = remote_smtp
35292 You can use the smart host's IP address instead of the name if you wish.
35293 If you are using Exim only to submit messages to a smart host, and not for
35294 receiving incoming messages, you can arrange for it to do the submission
35295 synchronously by setting the &%mua_wrapper%& option (see chapter
35296 &<<CHAPnonqueueing>>&).
35301 .section "Using Exim to handle mailing lists" "SECTmailinglists"
35302 .cindex "mailing lists"
35303 Exim can be used to run simple mailing lists, but for large and/or complicated
35304 requirements, the use of additional specialized mailing list software such as
35305 Majordomo or Mailman is recommended.
35307 The &(redirect)& router can be used to handle mailing lists where each list
35308 is maintained in a separate file, which can therefore be managed by an
35309 independent manager. The &%domains%& router option can be used to run these
35310 lists in a separate domain from normal mail. For example:
35314 domains = lists.example
35315 file = /usr/lists/$local_part
35318 errors_to = $local_part-request@lists.example
35321 This router is skipped for domains other than &'lists.example'&. For addresses
35322 in that domain, it looks for a file that matches the local part. If there is no
35323 such file, the router declines, but because &%no_more%& is set, no subsequent
35324 routers are tried, and so the whole delivery fails.
35326 The &%forbid_pipe%& and &%forbid_file%& options prevent a local part from being
35327 expanded into a file name or a pipe delivery, which is usually inappropriate in
35330 .oindex "&%errors_to%&"
35331 The &%errors_to%& option specifies that any delivery errors caused by addresses
35332 taken from a mailing list are to be sent to the given address rather than the
35333 original sender of the message. However, before acting on this, Exim verifies
35334 the error address, and ignores it if verification fails.
35336 For example, using the configuration above, mail sent to
35337 &'dicts@lists.example'& is passed on to those addresses contained in
35338 &_/usr/lists/dicts_&, with error reports directed to
35339 &'dicts-request@lists.example'&, provided that this address can be verified.
35340 There could be a file called &_/usr/lists/dicts-request_& containing
35341 the address(es) of this particular list's manager(s), but other approaches,
35342 such as setting up an earlier router (possibly using the &%local_part_prefix%&
35343 or &%local_part_suffix%& options) to handle addresses of the form
35344 &%owner-%&&'xxx'& or &%xxx-%&&'request'&, are also possible.
35348 .section "Syntax errors in mailing lists" "SECID241"
35349 .cindex "mailing lists" "syntax errors in"
35350 If an entry in redirection data contains a syntax error, Exim normally defers
35351 delivery of the original address. That means that a syntax error in a mailing
35352 list holds up all deliveries to the list. This may not be appropriate when a
35353 list is being maintained automatically from data supplied by users, and the
35354 addresses are not rigorously checked.
35356 If the &%skip_syntax_errors%& option is set, the &(redirect)& router just skips
35357 entries that fail to parse, noting the incident in the log. If in addition
35358 &%syntax_errors_to%& is set to a verifiable address, a message is sent to it
35359 whenever a broken address is skipped. It is usually appropriate to set
35360 &%syntax_errors_to%& to the same address as &%errors_to%&.
35364 .section "Re-expansion of mailing lists" "SECID242"
35365 .cindex "mailing lists" "re-expansion of"
35366 Exim remembers every individual address to which a message has been delivered,
35367 in order to avoid duplication, but it normally stores only the original
35368 recipient addresses with a message. If all the deliveries to a mailing list
35369 cannot be done at the first attempt, the mailing list is re-expanded when the
35370 delivery is next tried. This means that alterations to the list are taken into
35371 account at each delivery attempt, so addresses that have been added to
35372 the list since the message arrived will therefore receive a copy of the
35373 message, even though it pre-dates their subscription.
35375 If this behaviour is felt to be undesirable, the &%one_time%& option can be set
35376 on the &(redirect)& router. If this is done, any addresses generated by the
35377 router that fail to deliver at the first attempt are added to the message as
35378 &"top level"& addresses, and the parent address that generated them is marked
35379 &"delivered"&. Thus, expansion of the mailing list does not happen again at the
35380 subsequent delivery attempts. The disadvantage of this is that if any of the
35381 failing addresses are incorrect, correcting them in the file has no effect on
35382 pre-existing messages.
35384 The original top-level address is remembered with each of the generated
35385 addresses, and is output in any log messages. However, any intermediate parent
35386 addresses are not recorded. This makes a difference to the log only if the
35387 &%all_parents%& selector is set, but for mailing lists there is normally only
35388 one level of expansion anyway.
35392 .section "Closed mailing lists" "SECID243"
35393 .cindex "mailing lists" "closed"
35394 The examples so far have assumed open mailing lists, to which anybody may
35395 send mail. It is also possible to set up closed lists, where mail is accepted
35396 from specified senders only. This is done by making use of the generic
35397 &%senders%& option to restrict the router that handles the list.
35399 The following example uses the same file as a list of recipients and as a list
35400 of permitted senders. It requires three routers:
35404 domains = lists.example
35405 local_part_suffix = -request
35406 file = /usr/lists/$local_part$local_part_suffix
35411 domains = lists.example
35412 senders = ${if exists {/usr/lists/$local_part}\
35413 {lsearch;/usr/lists/$local_part}{*}}
35414 file = /usr/lists/$local_part
35417 errors_to = $local_part-request@lists.example
35422 domains = lists.example
35424 data = :fail: $local_part@lists.example is a closed mailing list
35426 All three routers have the same &%domains%& setting, so for any other domains,
35427 they are all skipped. The first router runs only if the local part ends in
35428 &%-request%&. It handles messages to the list manager(s) by means of an open
35431 The second router runs only if the &%senders%& precondition is satisfied. It
35432 checks for the existence of a list that corresponds to the local part, and then
35433 checks that the sender is on the list by means of a linear search. It is
35434 necessary to check for the existence of the file before trying to search it,
35435 because otherwise Exim thinks there is a configuration error. If the file does
35436 not exist, the expansion of &%senders%& is *, which matches all senders. This
35437 means that the router runs, but because there is no list, declines, and
35438 &%no_more%& ensures that no further routers are run. The address fails with an
35439 &"unrouteable address"& error.
35441 The third router runs only if the second router is skipped, which happens when
35442 a mailing list exists, but the sender is not on it. This router forcibly fails
35443 the address, giving a suitable error message.
35448 .section "Variable Envelope Return Paths (VERP)" "SECTverp"
35450 .cindex "Variable Envelope Return Paths"
35451 .cindex "envelope sender"
35452 Variable Envelope Return Paths &-- see &url(http://cr.yp.to/proto/verp.txt) &--
35453 are a way of helping mailing list administrators discover which subscription
35454 address is the cause of a particular delivery failure. The idea is to encode
35455 the original recipient address in the outgoing envelope sender address, so that
35456 if the message is forwarded by another host and then subsequently bounces, the
35457 original recipient can be extracted from the recipient address of the bounce.
35459 .oindex &%errors_to%&
35460 .oindex &%return_path%&
35461 Envelope sender addresses can be modified by Exim using two different
35462 facilities: the &%errors_to%& option on a router (as shown in previous mailing
35463 list examples), or the &%return_path%& option on a transport. The second of
35464 these is effective only if the message is successfully delivered to another
35465 host; it is not used for errors detected on the local host (see the description
35466 of &%return_path%& in chapter &<<CHAPtransportgeneric>>&). Here is an example
35467 of the use of &%return_path%& to implement VERP on an &(smtp)& transport:
35473 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
35474 {$1-request+$local_part=$domain@your.dom.example}fail}
35476 This has the effect of rewriting the return path (envelope sender) on outgoing
35477 SMTP messages, if the local part of the original return path ends in
35478 &"-request"&, and the domain is &'your.dom.example'&. The rewriting inserts the
35479 local part and domain of the recipient into the return path. Suppose, for
35480 example, that a message whose return path has been set to
35481 &'somelist-request@your.dom.example'& is sent to
35482 &'subscriber@other.dom.example'&. In the transport, the return path is
35485 somelist-request+subscriber=other.dom.example@your.dom.example
35487 .vindex "&$local_part$&"
35488 For this to work, you must tell Exim to send multiple copies of messages that
35489 have more than one recipient, so that each copy has just one recipient. This is
35490 achieved by setting &%max_rcpt%& to 1. Without this, a single copy of a message
35491 might be sent to several different recipients in the same domain, in which case
35492 &$local_part$& is not available in the transport, because it is not unique.
35494 Unless your host is doing nothing but mailing list deliveries, you should
35495 probably use a separate transport for the VERP deliveries, so as not to use
35496 extra resources in making one-per-recipient copies for other deliveries. This
35497 can easily be done by expanding the &%transport%& option in the router:
35501 domains = ! +local_domains
35503 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}\
35504 {verp_smtp}{remote_smtp}}
35507 If you want to change the return path using &%errors_to%& in a router instead
35508 of using &%return_path%& in the transport, you need to set &%errors_to%& on all
35509 routers that handle mailing list addresses. This will ensure that all delivery
35510 errors, including those detected on the local host, are sent to the VERP
35513 On a host that does no local deliveries and has no manual routing, only the
35514 &(dnslookup)& router needs to be changed. A special transport is not needed for
35515 SMTP deliveries. Every mailing list recipient has its own return path value,
35516 and so Exim must hand them to the transport one at a time. Here is an example
35517 of a &(dnslookup)& router that implements VERP:
35521 domains = ! +local_domains
35522 transport = remote_smtp
35524 ${if match {$return_path}{^(.+?)-request@your.dom.example\$}}
35525 {$1-request+$local_part=$domain@your.dom.example}fail}
35528 Before you start sending out messages with VERPed return paths, you must also
35529 configure Exim to accept the bounce messages that come back to those paths.
35530 Typically this is done by setting a &%local_part_suffix%& option for a
35531 router, and using this to route the messages to wherever you want to handle
35534 The overhead incurred in using VERP depends very much on the size of the
35535 message, the number of recipient addresses that resolve to the same remote
35536 host, and the speed of the connection over which the message is being sent. If
35537 a lot of addresses resolve to the same host and the connection is slow, sending
35538 a separate copy of the message for each address may take substantially longer
35539 than sending a single copy with many recipients (for which VERP cannot be
35547 .section "Virtual domains" "SECTvirtualdomains"
35548 .cindex "virtual domains"
35549 .cindex "domain" "virtual"
35550 The phrase &'virtual domain'& is unfortunately used with two rather different
35554 A domain for which there are no real mailboxes; all valid local parts are
35555 aliases for other email addresses. Common examples are organizational
35556 top-level domains and &"vanity"& domains.
35558 One of a number of independent domains that are all handled by the same host,
35559 with mailboxes on that host, but where the mailbox owners do not necessarily
35560 have login accounts on that host.
35563 The first usage is probably more common, and does seem more &"virtual"& than
35564 the second. This kind of domain can be handled in Exim with a straightforward
35565 aliasing router. One approach is to create a separate alias file for each
35566 virtual domain. Exim can test for the existence of the alias file to determine
35567 whether the domain exists. The &(dsearch)& lookup type is useful here, leading
35568 to a router of this form:
35572 domains = dsearch;/etc/mail/virtual
35573 data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain}}
35576 The &%domains%& option specifies that the router is to be skipped, unless there
35577 is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
35578 domain that is being processed. When the router runs, it looks up the local
35579 part in the file to find a new address (or list of addresses). The &%no_more%&
35580 setting ensures that if the lookup fails (leading to &%data%& being an empty
35581 string), Exim gives up on the address without trying any subsequent routers.
35583 This one router can handle all the virtual domains because the alias file names
35584 follow a fixed pattern. Permissions can be arranged so that appropriate people
35585 can edit the different alias files. A successful aliasing operation results in
35586 a new envelope recipient address, which is then routed from scratch.
35588 The other kind of &"virtual"& domain can also be handled in a straightforward
35589 way. One approach is to create a file for each domain containing a list of
35590 valid local parts, and use it in a router like this:
35594 domains = dsearch;/etc/mail/domains
35595 local_parts = lsearch;/etc/mail/domains/$domain
35596 transport = my_mailboxes
35598 The address is accepted if there is a file for the domain, and the local part
35599 can be found in the file. The &%domains%& option is used to check for the
35600 file's existence because &%domains%& is tested before the &%local_parts%&
35601 option (see section &<<SECTrouprecon>>&). You cannot use &%require_files%&,
35602 because that option is tested after &%local_parts%&. The transport is as
35606 driver = appendfile
35607 file = /var/mail/$domain/$local_part
35610 This uses a directory of mailboxes for each domain. The &%user%& setting is
35611 required, to specify which uid is to be used for writing to the mailboxes.
35613 The configuration shown here is just one example of how you might support this
35614 requirement. There are many other ways this kind of configuration can be set
35615 up, for example, by using a database instead of separate files to hold all the
35616 information about the domains.
35620 .section "Multiple user mailboxes" "SECTmulbox"
35621 .cindex "multiple mailboxes"
35622 .cindex "mailbox" "multiple"
35623 .cindex "local part" "prefix"
35624 .cindex "local part" "suffix"
35625 Heavy email users often want to operate with multiple mailboxes, into which
35626 incoming mail is automatically sorted. A popular way of handling this is to
35627 allow users to use multiple sender addresses, so that replies can easily be
35628 identified. Users are permitted to add prefixes or suffixes to their local
35629 parts for this purpose. The wildcard facility of the generic router options
35630 &%local_part_prefix%& and &%local_part_suffix%& can be used for this. For
35631 example, consider this router:
35636 file = $home/.forward
35637 local_part_suffix = -*
35638 local_part_suffix_optional
35641 .vindex "&$local_part_suffix$&"
35642 It runs a user's &_.forward_& file for all local parts of the form
35643 &'username-*'&. Within the filter file the user can distinguish different
35644 cases by testing the variable &$local_part_suffix$&. For example:
35646 if $local_part_suffix contains -special then
35647 save /home/$local_part/Mail/special
35650 If the filter file does not exist, or does not deal with such addresses, they
35651 fall through to subsequent routers, and, assuming no subsequent use of the
35652 &%local_part_suffix%& option is made, they presumably fail. Thus, users have
35653 control over which suffixes are valid.
35655 Alternatively, a suffix can be used to trigger the use of a different
35656 &_.forward_& file &-- which is the way a similar facility is implemented in
35662 file = $home/.forward$local_part_suffix
35663 local_part_suffix = -*
35664 local_part_suffix_optional
35667 If there is no suffix, &_.forward_& is used; if the suffix is &'-special'&, for
35668 example, &_.forward-special_& is used. Once again, if the appropriate file
35669 does not exist, or does not deal with the address, it is passed on to
35670 subsequent routers, which could, if required, look for an unqualified
35671 &_.forward_& file to use as a default.
35675 .section "Simplified vacation processing" "SECID244"
35676 .cindex "vacation processing"
35677 The traditional way of running the &'vacation'& program is for a user to set up
35678 a pipe command in a &_.forward_& file
35679 (see section &<<SECTspecitredli>>& for syntax details).
35680 This is prone to error by inexperienced users. There are two features of Exim
35681 that can be used to make this process simpler for users:
35684 A local part prefix such as &"vacation-"& can be specified on a router which
35685 can cause the message to be delivered directly to the &'vacation'& program, or
35686 alternatively can use Exim's &(autoreply)& transport. The contents of a user's
35687 &_.forward_& file are then much simpler. For example:
35689 spqr, vacation-spqr
35692 The &%require_files%& generic router option can be used to trigger a
35693 vacation delivery by checking for the existence of a certain file in the
35694 user's home directory. The &%unseen%& generic option should also be used, to
35695 ensure that the original delivery also proceeds. In this case, all the user has
35696 to do is to create a file called, say, &_.vacation_&, containing a vacation
35700 Another advantage of both these methods is that they both work even when the
35701 use of arbitrary pipes by users is locked out.
35705 .section "Taking copies of mail" "SECID245"
35706 .cindex "message" "copying every"
35707 Some installations have policies that require archive copies of all messages to
35708 be made. A single copy of each message can easily be taken by an appropriate
35709 command in a system filter, which could, for example, use a different file for
35710 each day's messages.
35712 There is also a shadow transport mechanism that can be used to take copies of
35713 messages that are successfully delivered by local transports, one copy per
35714 delivery. This could be used, &'inter alia'&, to implement automatic
35715 notification of delivery by sites that insist on doing such things.
35719 .section "Intermittently connected hosts" "SECID246"
35720 .cindex "intermittently connected hosts"
35721 It has become quite common (because it is cheaper) for hosts to connect to the
35722 Internet periodically rather than remain connected all the time. The normal
35723 arrangement is that mail for such hosts accumulates on a system that is
35724 permanently connected.
35726 Exim was designed for use on permanently connected hosts, and so it is not
35727 particularly well-suited to use in an intermittently connected environment.
35728 Nevertheless there are some features that can be used.
35731 .section "Exim on the upstream server host" "SECID247"
35732 It is tempting to arrange for incoming mail for the intermittently connected
35733 host to remain on Exim's queue until the client connects. However, this
35734 approach does not scale very well. Two different kinds of waiting message are
35735 being mixed up in the same queue &-- those that cannot be delivered because of
35736 some temporary problem, and those that are waiting for their destination host
35737 to connect. This makes it hard to manage the queue, as well as wasting
35738 resources, because each queue runner scans the entire queue.
35740 A better approach is to separate off those messages that are waiting for an
35741 intermittently connected host. This can be done by delivering these messages
35742 into local files in batch SMTP, &"mailstore"&, or other envelope-preserving
35743 format, from where they are transmitted by other software when their
35744 destination connects. This makes it easy to collect all the mail for one host
35745 in a single directory, and to apply local timeout rules on a per-message basis
35748 On a very small scale, leaving the mail on Exim's queue can be made to work. If
35749 you are doing this, you should configure Exim with a long retry period for the
35750 intermittent host. For example:
35752 cheshire.wonderland.fict.example * F,5d,24h
35754 This stops a lot of failed delivery attempts from occurring, but Exim remembers
35755 which messages it has queued up for that host. Once the intermittent host comes
35756 online, forcing delivery of one message (either by using the &%-M%& or &%-R%&
35757 options, or by using the ETRN SMTP command (see section &<<SECTETRN>>&)
35758 causes all the queued up messages to be delivered, often down a single SMTP
35759 connection. While the host remains connected, any new messages get delivered
35762 If the connecting hosts do not have fixed IP addresses, that is, if a host is
35763 issued with a different IP address each time it connects, Exim's retry
35764 mechanisms on the holding host get confused, because the IP address is normally
35765 used as part of the key string for holding retry information. This can be
35766 avoided by unsetting &%retry_include_ip_address%& on the &(smtp)& transport.
35767 Since this has disadvantages for permanently connected hosts, it is best to
35768 arrange a separate transport for the intermittently connected ones.
35772 .section "Exim on the intermittently connected client host" "SECID248"
35773 The value of &%smtp_accept_queue_per_connection%& should probably be
35774 increased, or even set to zero (that is, disabled) on the intermittently
35775 connected host, so that all incoming messages down a single connection get
35776 delivered immediately.
35778 .cindex "SMTP" "passed connection"
35779 .cindex "SMTP" "multiple deliveries"
35780 .cindex "multiple SMTP deliveries"
35781 Mail waiting to be sent from an intermittently connected host will probably
35782 not have been routed, because without a connection DNS lookups are not
35783 possible. This means that if a normal queue run is done at connection time,
35784 each message is likely to be sent in a separate SMTP session. This can be
35785 avoided by starting the queue run with a command line option beginning with
35786 &%-qq%& instead of &%-q%&. In this case, the queue is scanned twice. In the
35787 first pass, routing is done but no deliveries take place. The second pass is a
35788 normal queue run; since all the messages have been previously routed, those
35789 destined for the same host are likely to get sent as multiple deliveries in a
35790 single SMTP connection.
35794 . ////////////////////////////////////////////////////////////////////////////
35795 . ////////////////////////////////////////////////////////////////////////////
35797 .chapter "Using Exim as a non-queueing client" "CHAPnonqueueing" &&&
35798 "Exim as a non-queueing client"
35799 .cindex "client, non-queueing"
35800 .cindex "smart host" "suppressing queueing"
35801 On a personal computer, it is a common requirement for all
35802 email to be sent to a &"smart host"&. There are plenty of MUAs that can be
35803 configured to operate that way, for all the popular operating systems.
35804 However, there are some MUAs for Unix-like systems that cannot be so
35805 configured: they submit messages using the command line interface of
35806 &_/usr/sbin/sendmail_&. Furthermore, utility programs such as &'cron'& submit
35809 If the personal computer runs continuously, there is no problem, because it can
35810 run a conventional MTA that handles delivery to the smart host, and deal with
35811 any delays via its queueing mechanism. However, if the computer does not run
35812 continuously or runs different operating systems at different times, queueing
35813 email is not desirable.
35815 There is therefore a requirement for something that can provide the
35816 &_/usr/sbin/sendmail_& interface but deliver messages to a smart host without
35817 any queueing or retrying facilities. Furthermore, the delivery to the smart
35818 host should be synchronous, so that if it fails, the sending MUA is immediately
35819 informed. In other words, we want something that extends an MUA that submits
35820 to a local MTA via the command line so that it behaves like one that submits
35821 to a remote smart host using TCP/SMTP.
35823 There are a number of applications (for example, there is one called &'ssmtp'&)
35824 that do this job. However, people have found them to be lacking in various
35825 ways. For instance, you might want to allow aliasing and forwarding to be done
35826 before sending a message to the smart host.
35828 Exim already had the necessary infrastructure for doing this job. Just a few
35829 tweaks were needed to make it behave as required, though it is somewhat of an
35830 overkill to use a fully-featured MTA for this purpose.
35832 .oindex "&%mua_wrapper%&"
35833 There is a Boolean global option called &%mua_wrapper%&, defaulting false.
35834 Setting &%mua_wrapper%& true causes Exim to run in a special mode where it
35835 assumes that it is being used to &"wrap"& a command-line MUA in the manner
35836 just described. As well as setting &%mua_wrapper%&, you also need to provide a
35837 compatible router and transport configuration. Typically there will be just one
35838 router and one transport, sending everything to a smart host.
35840 When run in MUA wrapping mode, the behaviour of Exim changes in the
35844 A daemon cannot be run, nor will Exim accept incoming messages from &'inetd'&.
35845 In other words, the only way to submit messages is via the command line.
35847 Each message is synchronously delivered as soon as it is received (&%-odi%& is
35848 assumed). All queueing options (&%queue_only%&, &%queue_smtp_domains%&,
35849 &%control%& in an ACL, etc.) are quietly ignored. The Exim reception process
35850 does not finish until the delivery attempt is complete. If the delivery is
35851 successful, a zero return code is given.
35853 Address redirection is permitted, but the final routing for all addresses must
35854 be to the same remote transport, and to the same list of hosts. Furthermore,
35855 the return address (envelope sender) must be the same for all recipients, as
35856 must any added or deleted header lines. In other words, it must be possible to
35857 deliver the message in a single SMTP transaction, however many recipients there
35860 If these conditions are not met, or if routing any address results in a
35861 failure or defer status, or if Exim is unable to deliver all the recipients
35862 successfully to one of the smart hosts, delivery of the entire message fails.
35864 Because no queueing is allowed, all failures are treated as permanent; there
35865 is no distinction between 4&'xx'& and 5&'xx'& SMTP response codes from the
35866 smart host. Furthermore, because only a single yes/no response can be given to
35867 the caller, it is not possible to deliver to some recipients and not others. If
35868 there is an error (temporary or permanent) for any recipient, all are failed.
35870 If more than one smart host is listed, Exim will try another host after a
35871 connection failure or a timeout, in the normal way. However, if this kind of
35872 failure happens for all the hosts, the delivery fails.
35874 When delivery fails, an error message is written to the standard error stream
35875 (as well as to Exim's log), and Exim exits to the caller with a return code
35876 value 1. The message is expunged from Exim's spool files. No bounce messages
35877 are ever generated.
35879 No retry data is maintained, and any retry rules are ignored.
35881 A number of Exim options are overridden: &%deliver_drop_privilege%& is forced
35882 true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&,
35883 &%remote_max_parallel%& is forced to one, and fallback hosts are ignored.
35886 The overall effect is that Exim makes a single synchronous attempt to deliver
35887 the message, failing if there is any kind of problem. Because no local
35888 deliveries are done and no daemon can be run, Exim does not need root
35889 privilege. It should be possible to run it setuid to &'exim'& instead of setuid
35890 to &'root'&. See section &<<SECTrunexiwitpri>>& for a general discussion about
35891 the advantages and disadvantages of running without root privilege.
35896 . ////////////////////////////////////////////////////////////////////////////
35897 . ////////////////////////////////////////////////////////////////////////////
35899 .chapter "Log files" "CHAPlog"
35900 .scindex IIDloggen "log" "general description"
35901 .cindex "log" "types of"
35902 Exim writes three different logs, referred to as the main log, the reject log,
35907 The main log records the arrival of each message and each delivery in a single
35908 line in each case. The format is as compact as possible, in an attempt to keep
35909 down the size of log files. Two-character flag sequences make it easy to pick
35910 out these lines. A number of other events are recorded in the main log. Some of
35911 them are optional, in which case the &%log_selector%& option controls whether
35912 they are included or not. A Perl script called &'eximstats'&, which does simple
35913 analysis of main log files, is provided in the Exim distribution (see section
35914 &<<SECTmailstat>>&).
35916 .cindex "reject log"
35917 The reject log records information from messages that are rejected as a result
35918 of a configuration option (that is, for policy reasons).
35919 The first line of each rejection is a copy of the line that is also written to
35920 the main log. Then, if the message's header has been read at the time the log
35921 is written, its contents are written to this log. Only the original header
35922 lines are available; header lines added by ACLs are not logged. You can use the
35923 reject log to check that your policy controls are working correctly; on a busy
35924 host this may be easier than scanning the main log for rejection messages. You
35925 can suppress the writing of the reject log by setting &%write_rejectlog%&
35928 .cindex "panic log"
35929 .cindex "system log"
35930 When certain serious errors occur, Exim writes entries to its panic log. If the
35931 error is sufficiently disastrous, Exim bombs out afterwards. Panic log entries
35932 are usually written to the main log as well, but can get lost amid the mass of
35933 other entries. The panic log should be empty under normal circumstances. It is
35934 therefore a good idea to check it (or to have a &'cron'& script check it)
35935 regularly, in order to become aware of any problems. When Exim cannot open its
35936 panic log, it tries as a last resort to write to the system log (syslog). This
35937 is opened with LOG_PID+LOG_CONS and the facility code of LOG_MAIL. The
35938 message itself is written at priority LOG_CRIT.
35941 Every log line starts with a timestamp, in the format shown in the following
35942 example. Note that many of the examples shown in this chapter are line-wrapped.
35943 In the log file, this would be all on one line:
35945 2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed
35948 By default, the timestamps are in the local timezone. There are two
35949 ways of changing this:
35952 You can set the &%timezone%& option to a different time zone; in particular, if
35957 the timestamps will be in UTC (aka GMT).
35959 If you set &%log_timezone%& true, the time zone is added to the timestamp, for
35962 2003-04-25 11:17:07 +0100 Start queue run: pid=12762
35966 .cindex "log" "process ids in"
35967 .cindex "pid (process id)" "in log lines"
35968 Exim does not include its process id in log lines by default, but you can
35969 request that it does so by specifying the &`pid`& log selector (see section
35970 &<<SECTlogselector>>&). When this is set, the process id is output, in square
35971 brackets, immediately after the time and date.
35976 .section "Where the logs are written" "SECTwhelogwri"
35977 .cindex "log" "destination"
35978 .cindex "log" "to file"
35979 .cindex "log" "to syslog"
35981 The logs may be written to local files, or to syslog, or both. However, it
35982 should be noted that many syslog implementations use UDP as a transport, and
35983 are therefore unreliable in the sense that messages are not guaranteed to
35984 arrive at the loghost, nor is the ordering of messages necessarily maintained.
35985 It has also been reported that on large log files (tens of megabytes) you may
35986 need to tweak syslog to prevent it syncing the file with each write &-- on
35987 Linux this has been seen to make syslog take 90% plus of CPU time.
35989 The destination for Exim's logs is configured by setting LOG_FILE_PATH in
35990 &_Local/Makefile_& or by setting &%log_file_path%& in the run time
35991 configuration. This latter string is expanded, so it can contain, for example,
35992 references to the host name:
35994 log_file_path = /var/log/$primary_hostname/exim_%slog
35996 It is generally advisable, however, to set the string in &_Local/Makefile_&
35997 rather than at run time, because then the setting is available right from the
35998 start of Exim's execution. Otherwise, if there's something it wants to log
35999 before it has read the configuration file (for example, an error in the
36000 configuration file) it will not use the path you want, and may not be able to
36003 The value of LOG_FILE_PATH or &%log_file_path%& is a colon-separated
36004 list, currently limited to at most two items. This is one option where the
36005 facility for changing a list separator may not be used. The list must always be
36006 colon-separated. If an item in the list is &"syslog"& then syslog is used;
36007 otherwise the item must either be an absolute path, containing &`%s`& at the
36008 point where &"main"&, &"reject"&, or &"panic"& is to be inserted, or be empty,
36009 implying the use of a default path.
36011 When Exim encounters an empty item in the list, it searches the list defined by
36012 LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
36013 &"syslog"&. This means that an empty item in &%log_file_path%& can be used to
36014 mean &"use the path specified at build time"&. It no such item exists, log
36015 files are written in the &_log_& subdirectory of the spool directory. This is
36016 equivalent to the setting:
36018 log_file_path = $spool_directory/log/%slog
36020 If you do not specify anything at build time or run time,
36021 or if you unset the option at run time (i.e. &`log_file_path = `&),
36022 that is where the logs are written.
36024 A log file path may also contain &`%D`& or &`%M`& if datestamped log file names
36025 are in use &-- see section &<<SECTdatlogfil>>& below.
36027 Here are some examples of possible settings:
36029 &`LOG_FILE_PATH=syslog `& syslog only
36030 &`LOG_FILE_PATH=:syslog `& syslog and default path
36031 &`LOG_FILE_PATH=syslog : /usr/log/exim_%s `& syslog and specified path
36032 &`LOG_FILE_PATH=/usr/log/exim_%s `& specified path only
36034 If there are more than two paths in the list, the first is used and a panic
36039 .section "Logging to local files that are periodically &""cycled""&" "SECID285"
36040 .cindex "log" "cycling local files"
36041 .cindex "cycling logs"
36042 .cindex "&'exicyclog'&"
36043 .cindex "log" "local files; writing to"
36044 Some operating systems provide centralized and standardized methods for cycling
36045 log files. For those that do not, a utility script called &'exicyclog'& is
36046 provided (see section &<<SECTcyclogfil>>&). This renames and compresses the
36047 main and reject logs each time it is called. The maximum number of old logs to
36048 keep can be set. It is suggested this script is run as a daily &'cron'& job.
36050 An Exim delivery process opens the main log when it first needs to write to it,
36051 and it keeps the file open in case subsequent entries are required &-- for
36052 example, if a number of different deliveries are being done for the same
36053 message. However, remote SMTP deliveries can take a long time, and this means
36054 that the file may be kept open long after it is renamed if &'exicyclog'& or
36055 something similar is being used to rename log files on a regular basis. To
36056 ensure that a switch of log files is noticed as soon as possible, Exim calls
36057 &[stat()]& on the main log's name before reusing an open file, and if the file
36058 does not exist, or its inode has changed, the old file is closed and Exim
36059 tries to open the main log from scratch. Thus, an old log file may remain open
36060 for quite some time, but no Exim processes should write to it once it has been
36065 .section "Datestamped log files" "SECTdatlogfil"
36066 .cindex "log" "datestamped files"
36067 Instead of cycling the main and reject log files by renaming them
36068 periodically, some sites like to use files whose names contain a datestamp,
36069 for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or
36070 &_yyyymm_&. Exim has support for this way of working. It is enabled by setting
36071 the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the
36072 point where the datestamp is required. For example:
36074 log_file_path = /var/spool/exim/log/%slog-%D
36075 log_file_path = /var/log/exim-%s-%D.log
36076 log_file_path = /var/spool/exim/log/%D-%slog
36077 log_file_path = /var/log/exim/%s.%M
36079 As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are
36080 examples of names generated by the above examples:
36082 /var/spool/exim/log/mainlog-20021225
36083 /var/log/exim-reject-20021225.log
36084 /var/spool/exim/log/20021225-mainlog
36085 /var/log/exim/main.200212
36087 When this form of log file is specified, Exim automatically switches to new
36088 files at midnight. It does not make any attempt to compress old logs; you
36089 will need to write your own script if you require this. You should not
36090 run &'exicyclog'& with this form of logging.
36092 The location of the panic log is also determined by &%log_file_path%&, but it
36093 is not datestamped, because rotation of the panic log does not make sense.
36094 When generating the name of the panic log, &`%D`& or &`%M`& are removed from
36095 the string. In addition, if it immediately follows a slash, a following
36096 non-alphanumeric character is removed; otherwise a preceding non-alphanumeric
36097 character is removed. Thus, the four examples above would give these panic
36100 /var/spool/exim/log/paniclog
36101 /var/log/exim-panic.log
36102 /var/spool/exim/log/paniclog
36103 /var/log/exim/panic
36107 .section "Logging to syslog" "SECID249"
36108 .cindex "log" "syslog; writing to"
36109 The use of syslog does not change what Exim logs or the format of its messages,
36110 except in one respect. If &%syslog_timestamp%& is set false, the timestamps on
36111 Exim's log lines are omitted when these lines are sent to syslog. Apart from
36112 that, the same strings are written to syslog as to log files. The syslog
36113 &"facility"& is set to LOG_MAIL, and the program name to &"exim"&
36114 by default, but you can change these by setting the &%syslog_facility%& and
36115 &%syslog_processname%& options, respectively. If Exim was compiled with
36116 SYSLOG_LOG_PID set in &_Local/Makefile_& (this is the default in
36117 &_src/EDITME_&), then, on systems that permit it (all except ULTRIX), the
36118 LOG_PID flag is set so that the &[syslog()]& call adds the pid as well as
36119 the time and host name to each line.
36120 The three log streams are mapped onto syslog priorities as follows:
36123 &'mainlog'& is mapped to LOG_INFO
36125 &'rejectlog'& is mapped to LOG_NOTICE
36127 &'paniclog'& is mapped to LOG_ALERT
36130 Many log lines are written to both &'mainlog'& and &'rejectlog'&, and some are
36131 written to both &'mainlog'& and &'paniclog'&, so there will be duplicates if
36132 these are routed by syslog to the same place. You can suppress this duplication
36133 by setting &%syslog_duplication%& false.
36135 Exim's log lines can sometimes be very long, and some of its &'rejectlog'&
36136 entries contain multiple lines when headers are included. To cope with both
36137 these cases, entries written to syslog are split into separate &[syslog()]&
36138 calls at each internal newline, and also after a maximum of
36139 870 data characters. (This allows for a total syslog line length of 1024, when
36140 additions such as timestamps are added.) If you are running a syslog
36141 replacement that can handle lines longer than the 1024 characters allowed by
36142 RFC 3164, you should set
36144 SYSLOG_LONG_LINES=yes
36146 in &_Local/Makefile_& before building Exim. That stops Exim from splitting long
36147 lines, but it still splits at internal newlines in &'reject'& log entries.
36149 To make it easy to re-assemble split lines later, each component of a split
36150 entry starts with a string of the form [<&'n'&>/<&'m'&>] or [<&'n'&>\<&'m'&>]
36151 where <&'n'&> is the component number and <&'m'&> is the total number of
36152 components in the entry. The / delimiter is used when the line was split
36153 because it was too long; if it was split because of an internal newline, the \
36154 delimiter is used. For example, supposing the length limit to be 50 instead of
36155 870, the following would be the result of a typical rejection message to
36156 &'mainlog'& (LOG_INFO), each line in addition being preceded by the time, host
36157 name, and pid as added by syslog:
36159 [1/5] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from
36160 [2/5] [127.0.0.1] (ph10): syntax error in 'From' header
36161 [3/5] when scanning for sender: missing or malformed lo
36162 [4/5] cal part in "<>" (envelope sender is <ph10@cam.exa
36165 The same error might cause the following lines to be written to &"rejectlog"&
36168 [1/18] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected fro
36169 [2/18] m [127.0.0.1] (ph10): syntax error in 'From' head
36170 [3/18] er when scanning for sender: missing or malformed
36171 [4/18] local part in "<>" (envelope sender is <ph10@cam
36173 [6\18] Recipients: ph10@some.domain.cam.example
36174 [7\18] P Received: from [127.0.0.1] (ident=ph10)
36175 [8\18] by xxxxx.cam.example with smtp (Exim 4.00)
36176 [9\18] id 16RdAL-0006pc-00
36177 [10/18] for ph10@cam.example; Mon, 16 Sep 2002 16:
36178 [11\18] 09:43 +0100
36180 [13\18] Subject: this is a test header
36181 [18\18] X-something: this is another header
36182 [15/18] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.examp
36185 [18/18] Date: Mon, 16 Sep 2002 16:09:43 +0100
36187 Log lines that are neither too long nor contain newlines are written to syslog
36188 without modification.
36190 If only syslog is being used, the Exim monitor is unable to provide a log tail
36191 display, unless syslog is routing &'mainlog'& to a file on the local host and
36192 the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor
36197 .section "Log line flags" "SECID250"
36198 One line is written to the main log for each message received, and for each
36199 successful, unsuccessful, and delayed delivery. These lines can readily be
36200 picked out by the distinctive two-character flags that immediately follow the
36201 timestamp. The flags are:
36203 &`<=`& message arrival
36204 &`(=`& message fakereject
36205 &`=>`& normal message delivery
36206 &`->`& additional address in same delivery
36207 &`>>`& cutthrough message delivery
36208 &`*>`& delivery suppressed by &%-N%&
36209 &`**`& delivery failed; address bounced
36210 &`==`& delivery deferred; temporary problem
36214 .section "Logging message reception" "SECID251"
36215 .cindex "log" "reception line"
36216 The format of the single-line entry in the main log that is written for every
36217 message received is shown in the basic example below, which is split over
36218 several lines in order to fit it on the page:
36220 2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example
36221 H=mailer.fict.example [192.168.123.123] U=exim
36222 P=smtp S=5678 id=<incoming message id>
36224 The address immediately following &"<="& is the envelope sender address. A
36225 bounce message is shown with the sender address &"<>"&, and if it is locally
36226 generated, this is followed by an item of the form
36230 which is a reference to the message that caused the bounce to be sent.
36234 For messages from other hosts, the H and U fields identify the remote host and
36235 record the RFC 1413 identity of the user that sent the message, if one was
36236 received. The number given in square brackets is the IP address of the sending
36237 host. If there is a single, unparenthesized host name in the H field, as
36238 above, it has been verified to correspond to the IP address (see the
36239 &%host_lookup%& option). If the name is in parentheses, it was the name quoted
36240 by the remote host in the SMTP HELO or EHLO command, and has not been
36241 verified. If verification yields a different name to that given for HELO or
36242 EHLO, the verified name appears first, followed by the HELO or EHLO
36243 name in parentheses.
36245 Misconfigured hosts (and mail forgers) sometimes put an IP address, with or
36246 without brackets, in the HELO or EHLO command, leading to entries in
36247 the log containing text like these examples:
36249 H=(10.21.32.43) [192.168.8.34]
36250 H=([10.21.32.43]) [192.168.8.34]
36252 This can be confusing. Only the final address in square brackets can be relied
36255 For locally generated messages (that is, messages not received over TCP/IP),
36256 the H field is omitted, and the U field contains the login name of the caller
36259 .cindex "authentication" "logging"
36260 .cindex "AUTH" "logging"
36261 For all messages, the P field specifies the protocol used to receive the
36262 message. This is the value that is stored in &$received_protocol$&. In the case
36263 of incoming SMTP messages, the value indicates whether or not any SMTP
36264 extensions (ESMTP), encryption, or authentication were used. If the SMTP
36265 session was encrypted, there is an additional X field that records the cipher
36266 suite that was used.
36268 .cindex log protocol
36269 The protocol is set to &"esmtpsa"& or &"esmtpa"& for messages received from
36270 hosts that have authenticated themselves using the SMTP AUTH command. The first
36271 value is used when the SMTP connection was encrypted (&"secure"&). In this case
36272 there is an additional item A= followed by the name of the authenticator that
36273 was used. If an authenticated identification was set up by the authenticator's
36274 &%server_set_id%& option, this is logged too, separated by a colon from the
36275 authenticator name.
36277 .cindex "size" "of message"
36278 The id field records the existing message id, if present. The size of the
36279 received message is given by the S field. When the message is delivered,
36280 headers may be removed or added, so that the size of delivered copies of the
36281 message may not correspond with this value (and indeed may be different to each
36284 The &%log_selector%& option can be used to request the logging of additional
36285 data when a message is received. See section &<<SECTlogselector>>& below.
36289 .section "Logging deliveries" "SECID252"
36290 .cindex "log" "delivery line"
36291 The format of the single-line entry in the main log that is written for every
36292 delivery is shown in one of the examples below, for local and remote
36293 deliveries, respectively. Each example has been split into multiple lines in order
36294 to fit it on the page:
36296 2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv
36297 <marv@hitch.fict.example> R=localuser T=local_delivery
36298 2002-10-31 09:00:10 16ZCW1-0005MB-00 =>
36299 monk@holistic.fict.example R=dnslookup T=remote_smtp
36300 H=holistic.fict.example [192.168.234.234]
36302 For ordinary local deliveries, the original address is given in angle brackets
36303 after the final delivery address, which might be a pipe or a file. If
36304 intermediate address(es) exist between the original and the final address, the
36305 last of these is given in parentheses after the final address. The R and T
36306 fields record the router and transport that were used to process the address.
36308 If SMTP AUTH was used for the delivery there is an additional item A=
36309 followed by the name of the authenticator that was used.
36310 If an authenticated identification was set up by the authenticator's &%client_set_id%&
36311 option, this is logged too, separated by a colon from the authenticator name.
36313 If a shadow transport was run after a successful local delivery, the log line
36314 for the successful delivery has an item added on the end, of the form
36316 &`ST=<`&&'shadow transport name'&&`>`&
36318 If the shadow transport did not succeed, the error message is put in
36319 parentheses afterwards.
36321 .cindex "asterisk" "after IP address"
36322 When more than one address is included in a single delivery (for example, two
36323 SMTP RCPT commands in one transaction) the second and subsequent addresses are
36324 flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
36325 down a single SMTP connection, an asterisk follows the IP address in the log
36326 lines for the second and subsequent messages.
36327 When two or more messages are delivered down a single TLS connection, the
36328 DNS and some TLS-related information logged for the first message delivered
36329 will not be present in the log lines for the second and subsequent messages.
36330 TLS cipher information is still available.
36332 .cindex "delivery" "cutthrough; logging"
36333 .cindex "cutthrough" "logging"
36334 When delivery is done in cutthrough mode it is flagged with &`>>`& and the log
36335 line precedes the reception line, since cutthrough waits for a possible
36336 rejection from the destination in case it can reject the sourced item.
36338 The generation of a reply message by a filter file gets logged as a
36339 &"delivery"& to the addressee, preceded by &">"&.
36341 The &%log_selector%& option can be used to request the logging of additional
36342 data when a message is delivered. See section &<<SECTlogselector>>& below.
36345 .section "Discarded deliveries" "SECID253"
36346 .cindex "discarded messages"
36347 .cindex "message" "discarded"
36348 .cindex "delivery" "discarded; logging"
36349 When a message is discarded as a result of the command &"seen finish"& being
36350 obeyed in a filter file which generates no deliveries, a log entry of the form
36352 2002-12-10 00:50:49 16auJc-0001UB-00 => discarded
36353 <low.club@bridge.example> R=userforward
36355 is written, to record why no deliveries are logged. When a message is discarded
36356 because it is aliased to &":blackhole:"& the log line is like this:
36358 1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole:
36359 <hole@nowhere.example> R=blackhole_router
36363 .section "Deferred deliveries" "SECID254"
36364 When a delivery is deferred, a line of the following form is logged:
36366 2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example
36367 R=dnslookup T=smtp defer (146): Connection refused
36369 In the case of remote deliveries, the error is the one that was given for the
36370 last IP address that was tried. Details of individual SMTP failures are also
36371 written to the log, so the above line would be preceded by something like
36373 2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to
36374 mail1.endrest.example [192.168.239.239]: Connection refused
36376 When a deferred address is skipped because its retry time has not been reached,
36377 a message is written to the log, but this can be suppressed by setting an
36378 appropriate value in &%log_selector%&.
36382 .section "Delivery failures" "SECID255"
36383 .cindex "delivery" "failure; logging"
36384 If a delivery fails because an address cannot be routed, a line of the
36385 following form is logged:
36387 1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example
36388 <jim@trek99.example>: unknown mail domain
36390 If a delivery fails at transport time, the router and transport are shown, and
36391 the response from the remote host is included, as in this example:
36393 2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example
36394 R=dnslookup T=remote_smtp: SMTP error from remote mailer
36395 after pipelined RCPT TO:<ace400@pb.example>: host
36396 pbmail3.py.example [192.168.63.111]: 553 5.3.0
36397 <ace400@pb.example>...Addressee unknown
36399 The word &"pipelined"& indicates that the SMTP PIPELINING extension was being
36400 used. See &%hosts_avoid_esmtp%& in the &(smtp)& transport for a way of
36401 disabling PIPELINING. The log lines for all forms of delivery failure are
36402 flagged with &`**`&.
36406 .section "Fake deliveries" "SECID256"
36407 .cindex "delivery" "fake; logging"
36408 If a delivery does not actually take place because the &%-N%& option has been
36409 used to suppress it, a normal delivery line is written to the log, except that
36410 &"=>"& is replaced by &"*>"&.
36414 .section "Completion" "SECID257"
36417 2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
36419 is written to the main log when a message is about to be removed from the spool
36420 at the end of its processing.
36425 .section "Summary of Fields in Log Lines" "SECID258"
36426 .cindex "log" "summary of fields"
36427 A summary of the field identifiers that are used in log lines is shown in
36428 the following table:
36430 &`A `& authenticator name (and optional id and sender)
36431 &`C `& SMTP confirmation on delivery
36432 &` `& command list for &"no mail in SMTP session"&
36433 &`CV `& certificate verification status
36434 &`D `& duration of &"no mail in SMTP session"&
36435 &`DKIM`& domain verified in incoming message
36436 &`DN `& distinguished name from peer certificate
36437 &`DS `& DNSSEC secured lookups
36438 &`DT `& on &`=>`& lines: time taken for a delivery
36439 &`F `& sender address (on delivery lines)
36440 &`H `& host name and IP address
36441 &`I `& local interface used
36442 &`K `& CHUNKING extension used
36443 &`id `& message id for incoming message
36444 &`M8S `& 8BITMIME status for incoming message
36445 &`P `& on &`<=`& lines: protocol used
36446 &` `& on &`=>`& and &`**`& lines: return path
36447 &`PRDR`& PRDR extension used
36448 &`PRX `& on &`<=`& and &`=>`& lines: proxy address
36449 &`Q `& alternate queue name
36450 &`QT `& on &`=>`& lines: time spent on queue so far
36451 &` `& on &"Completed"& lines: time spent on queue
36452 &`R `& on &`<=`& lines: reference for local bounce
36453 &` `& on &`=>`& &`>>`& &`**`& and &`==`& lines: router name
36454 &`RT `& on &`<=`& lines: time taken for reception
36455 &`S `& size of message in bytes
36456 &`SNI `& server name indication from TLS client hello
36457 &`ST `& shadow transport name
36458 &`T `& on &`<=`& lines: message subject (topic)
36459 &`TFO `& connection took advantage of TCP Fast Open
36460 &` `& on &`=>`& &`**`& and &`==`& lines: transport name
36461 &`U `& local user or RFC 1413 identity
36462 &`X `& TLS cipher suite
36466 .section "Other log entries" "SECID259"
36467 Various other types of log entry are written from time to time. Most should be
36468 self-explanatory. Among the more common are:
36471 .cindex "retry" "time not reached"
36472 &'retry time not reached'&&~&~An address previously suffered a temporary error
36473 during routing or local delivery, and the time to retry has not yet arrived.
36474 This message is not written to an individual message log file unless it happens
36475 during the first delivery attempt.
36477 &'retry time not reached for any host'&&~&~An address previously suffered
36478 temporary errors during remote delivery, and the retry time has not yet arrived
36479 for any of the hosts to which it is routed.
36481 .cindex "spool directory" "file locked"
36482 &'spool file locked'&&~&~An attempt to deliver a message cannot proceed because
36483 some other Exim process is already working on the message. This can be quite
36484 common if queue running processes are started at frequent intervals. The
36485 &'exiwhat'& utility script can be used to find out what Exim processes are
36488 .cindex "error" "ignored"
36489 &'error ignored'&&~&~There are several circumstances that give rise to this
36492 Exim failed to deliver a bounce message whose age was greater than
36493 &%ignore_bounce_errors_after%&. The bounce was discarded.
36495 A filter file set up a delivery using the &"noerror"& option, and the delivery
36496 failed. The delivery was discarded.
36498 A delivery set up by a router configured with
36499 . ==== As this is a nested list, any displays it contains must be indented
36500 . ==== as otherwise they are too far to the left.
36504 failed. The delivery was discarded.
36507 .cindex DKIM "log line"
36508 &'DKIM: d='&&~&~Verbose results of a DKIM verification attempt, if enabled for
36509 logging and the message has a DKIM signature header.
36516 .section "Reducing or increasing what is logged" "SECTlogselector"
36517 .cindex "log" "selectors"
36518 By setting the &%log_selector%& global option, you can disable some of Exim's
36519 default logging, or you can request additional logging. The value of
36520 &%log_selector%& is made up of names preceded by plus or minus characters. For
36523 log_selector = +arguments -retry_defer
36525 The list of optional log items is in the following table, with the default
36526 selection marked by asterisks:
36528 &` 8bitmime `& received 8BITMIME status
36529 &`*acl_warn_skipped `& skipped &%warn%& statement in ACL
36530 &` address_rewrite `& address rewriting
36531 &` all_parents `& all parents in => lines
36532 &` arguments `& command line arguments
36533 &`*connection_reject `& connection rejections
36534 &`*delay_delivery `& immediate delivery delayed
36535 &` deliver_time `& time taken to perform delivery
36536 &` delivery_size `& add &`S=`&&'nnn'& to => lines
36537 &`*dkim `& DKIM verified domain on <= lines
36538 &` dkim_verbose `& separate full DKIM verification result line, per signature
36539 &`*dnslist_defer `& defers of DNS list (aka RBL) lookups
36540 &` dnssec `& DNSSEC secured lookups
36541 &`*etrn `& ETRN commands
36542 &`*host_lookup_failed `& as it says
36543 &` ident_timeout `& timeout for ident connection
36544 &` incoming_interface `& local interface on <= and => lines
36545 &` incoming_port `& remote port on <= lines
36546 &`*lost_incoming_connection `& as it says (includes timeouts)
36547 &` millisec `& millisecond timestamps and RT,QT,DT,D times
36548 &` outgoing_interface `& local interface on => lines
36549 &` outgoing_port `& add remote port to => lines
36550 &`*queue_run `& start and end queue runs
36551 &` queue_time `& time on queue for one recipient
36552 &` queue_time_overall `& time on queue for whole message
36553 &` pid `& Exim process id
36554 &` proxy `& proxy address on <= and => lines
36555 &` receive_time `& time taken to receive message
36556 &` received_recipients `& recipients on <= lines
36557 &` received_sender `& sender on <= lines
36558 &`*rejected_header `& header contents on reject log
36559 &`*retry_defer `& &"retry time not reached"&
36560 &` return_path_on_delivery `& put return path on => and ** lines
36561 &` sender_on_delivery `& add sender to => lines
36562 &`*sender_verify_fail `& sender verification failures
36563 &`*size_reject `& rejection because too big
36564 &`*skip_delivery `& delivery skipped in a queue run
36565 &`*smtp_confirmation `& SMTP confirmation on => lines
36566 &` smtp_connection `& incoming SMTP connections
36567 &` smtp_incomplete_transaction`& incomplete SMTP transactions
36568 &` smtp_mailauth `& AUTH argument to MAIL commands
36569 &` smtp_no_mail `& session with no MAIL commands
36570 &` smtp_protocol_error `& SMTP protocol errors
36571 &` smtp_syntax_error `& SMTP syntax errors
36572 &` subject `& contents of &'Subject:'& on <= lines
36573 &`*tls_certificate_verified `& certificate verification status
36574 &`*tls_cipher `& TLS cipher suite on <= and => lines
36575 &` tls_peerdn `& TLS peer DN on <= and => lines
36576 &` tls_sni `& TLS SNI on <= lines
36577 &` unknown_in_list `& DNS lookup failed in list match
36579 &` all `& all of the above
36581 See also the &%slow_lookup_log%& main configuration option,
36582 section &<<SECID99>>&
36584 More details on each of these items follows:
36588 .cindex "log" "8BITMIME"
36589 &%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages,
36590 which may help in tracking down interoperability issues with ancient MTAs
36591 that are not 8bit clean. This is added to the &"<="& line, tagged with
36592 &`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given",
36593 &`7BIT`& and &`8BITMIME`& respectively.
36595 .cindex "&%warn%& ACL verb" "log when skipping"
36596 &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of
36597 its conditions cannot be evaluated, a log line to this effect is written if
36598 this log selector is set.
36600 .cindex "log" "rewriting"
36601 .cindex "rewriting" "logging"
36602 &%address_rewrite%&: This applies both to global rewrites and per-transport
36603 rewrites, but not to rewrites in filters run as an unprivileged user (because
36604 such users cannot access the log).
36606 .cindex "log" "full parentage"
36607 &%all_parents%&: Normally only the original and final addresses are logged on
36608 delivery lines; with this selector, intermediate parents are given in
36609 parentheses between them.
36611 .cindex "log" "Exim arguments"
36612 .cindex "Exim arguments, logging"
36613 &%arguments%&: This causes Exim to write the arguments with which it was called
36614 to the main log, preceded by the current working directory. This is a debugging
36615 feature, added to make it easier to find out how certain MUAs call
36616 &_/usr/sbin/sendmail_&. The logging does not happen if Exim has given up root
36617 privilege because it was called with the &%-C%& or &%-D%& options. Arguments
36618 that are empty or that contain white space are quoted. Non-printing characters
36619 are shown as escape sequences. This facility cannot log unrecognized arguments,
36620 because the arguments are checked before the configuration file is read. The
36621 only way to log such cases is to interpose a script such as &_util/logargs.sh_&
36622 between the caller and Exim.
36624 .cindex "log" "connection rejections"
36625 &%connection_reject%&: A log entry is written whenever an incoming SMTP
36626 connection is rejected, for whatever reason.
36628 .cindex "log" "delayed delivery"
36629 .cindex "delayed delivery, logging"
36630 &%delay_delivery%&: A log entry is written whenever a delivery process is not
36631 started for an incoming message because the load is too high or too many
36632 messages were received on one connection. Logging does not occur if no delivery
36633 process is started because &%queue_only%& is set or &%-odq%& was used.
36635 .cindex "log" "delivery duration"
36636 &%deliver_time%&: For each delivery, the amount of real time it has taken to
36637 perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
36638 If millisecond logging is enabled, short times will be shown with greater
36639 precision, eg. &`DT=0.304s`&.
36641 .cindex "log" "message size on delivery"
36642 .cindex "size" "of message"
36643 &%delivery_size%&: For each delivery, the size of message delivered is added to
36644 the &"=>"& line, tagged with S=.
36646 .cindex log "DKIM verification"
36647 .cindex DKIM "verification logging"
36648 &%dkim%&: For message acceptance log lines, when an DKIM signature in the header
36649 verifies successfully a tag of DKIM is added, with one of the verified domains.
36651 .cindex log "DKIM verification"
36652 .cindex DKIM "verification logging"
36653 &%dkim_verbose%&: A log entry is written for each attempted DKIM verification.
36655 .cindex "log" "dnslist defer"
36656 .cindex "DNS list" "logging defer"
36657 .cindex "black list (DNS)"
36658 &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a
36659 DNS black list suffers a temporary error.
36662 .cindex dnssec logging
36663 &%dnssec%&: For message acceptance and (attempted) delivery log lines, when
36664 dns lookups gave secure results a tag of DS is added.
36665 For acceptance this covers the reverse and forward lookups for host name verification.
36666 It does not cover helo-name verification.
36667 For delivery this covers the SRV, MX, A and/or AAAA lookups.
36669 .cindex "log" "ETRN commands"
36670 .cindex "ETRN" "logging"
36671 &%etrn%&: Every valid ETRN command that is received is logged, before the ACL
36672 is run to determine whether or not it is actually accepted. An invalid ETRN
36673 command, or one received within a message transaction is not logged by this
36674 selector (see &%smtp_syntax_error%& and &%smtp_protocol_error%&).
36676 .cindex "log" "host lookup failure"
36677 &%host_lookup_failed%&: When a lookup of a host's IP addresses fails to find
36678 any addresses, or when a lookup of an IP address fails to find a host name, a
36679 log line is written. This logging does not apply to direct DNS lookups when
36680 routing email addresses, but it does apply to &"byname"& lookups.
36682 .cindex "log" "ident timeout"
36683 .cindex "RFC 1413" "logging timeout"
36684 &%ident_timeout%&: A log line is written whenever an attempt to connect to a
36685 client's ident port times out.
36687 .cindex "log" "incoming interface"
36688 .cindex "log" "local interface"
36689 .cindex "log" "local address and port"
36690 .cindex "TCP/IP" "logging local address and port"
36691 .cindex "interface" "logging"
36692 &%incoming_interface%&: The interface on which a message was received is added
36693 to the &"<="& line as an IP address in square brackets, tagged by I= and
36694 followed by a colon and the port number. The local interface and port are also
36695 added to other SMTP log lines, for example &"SMTP connection from"&, to
36696 rejection lines, and (despite the name) to outgoing &"=>"& and &"->"& lines.
36697 The latter can be disabled by turning off the &%outgoing_interface%& option.
36699 .cindex log "incoming proxy address"
36700 .cindex proxy "logging proxy address"
36701 .cindex "TCP/IP" "logging proxy address"
36702 &%proxy%&: The internal (closest to the system running Exim) IP address
36703 of the proxy, tagged by PRX=, on the &"<="& line for a message accepted
36704 on a proxied connection
36705 or the &"=>"& line for a message delivered on a proxied connection.
36706 See &<<SECTproxyInbound>>& for more information.
36708 .cindex "log" "incoming remote port"
36709 .cindex "port" "logging remote"
36710 .cindex "TCP/IP" "logging incoming remote port"
36711 .vindex "&$sender_fullhost$&"
36712 .vindex "&$sender_rcvhost$&"
36713 &%incoming_port%&: The remote port number from which a message was received is
36714 added to log entries and &'Received:'& header lines, following the IP address
36715 in square brackets, and separated from it by a colon. This is implemented by
36716 changing the value that is put in the &$sender_fullhost$& and
36717 &$sender_rcvhost$& variables. Recording the remote port number has become more
36718 important with the widening use of NAT (see RFC 2505).
36720 .cindex "log" "dropped connection"
36721 &%lost_incoming_connection%&: A log line is written when an incoming SMTP
36722 connection is unexpectedly dropped.
36724 .cindex "log" "millisecond timestamps"
36725 .cindex millisecond logging
36726 .cindex timestamps "millisecond, in logs"
36727 &%millisec%&: Timestamps have a period and three decimal places of finer granularity
36728 appended to the seconds value.
36730 .cindex "log" "outgoing interface"
36731 .cindex "log" "local interface"
36732 .cindex "log" "local address and port"
36733 .cindex "TCP/IP" "logging local address and port"
36734 .cindex "interface" "logging"
36735 &%outgoing_interface%&: If &%incoming_interface%& is turned on, then the
36736 interface on which a message was sent is added to delivery lines as an I= tag
36737 followed by IP address in square brackets. You can disable this by turning
36738 off the &%outgoing_interface%& option.
36740 .cindex "log" "outgoing remote port"
36741 .cindex "port" "logging outgoing remote"
36742 .cindex "TCP/IP" "logging outgoing remote port"
36743 &%outgoing_port%&: The remote port number is added to delivery log lines (those
36744 containing => tags) following the IP address.
36745 The local port is also added if &%incoming_interface%& and
36746 &%outgoing_interface%& are both enabled.
36747 This option is not included in the default setting, because for most ordinary
36748 configurations, the remote port number is always 25 (the SMTP port), and the
36749 local port is a random ephemeral port.
36751 .cindex "log" "process ids in"
36752 .cindex "pid (process id)" "in log lines"
36753 &%pid%&: The current process id is added to every log line, in square brackets,
36754 immediately after the time and date.
36756 .cindex "log" "queue run"
36757 .cindex "queue runner" "logging"
36758 &%queue_run%&: The start and end of every queue run are logged.
36760 .cindex "log" "queue time"
36761 &%queue_time%&: The amount of time the message has been in the queue on the
36762 local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
36763 &`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
36764 includes reception time as well as the delivery time for the current address.
36765 This means that it may be longer than the difference between the arrival and
36766 delivery log line times, because the arrival log line is not written until the
36767 message has been successfully received.
36768 If millisecond logging is enabled, short times will be shown with greater
36769 precision, eg. &`QT=1.578s`&.
36771 &%queue_time_overall%&: The amount of time the message has been in the queue on
36772 the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
36773 example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
36774 message, so it includes reception time as well as the total delivery time.
36776 .cindex "log" "receive duration"
36777 &%receive_time%&: For each message, the amount of real time it has taken to
36778 perform the reception is logged as RT=<&'time'&>, for example, &`RT=1s`&.
36779 If millisecond logging is enabled, short times will be shown with greater
36780 precision, eg. &`RT=0.204s`&.
36782 .cindex "log" "recipients"
36783 &%received_recipients%&: The recipients of a message are listed in the main log
36784 as soon as the message is received. The list appears at the end of the log line
36785 that is written when a message is received, preceded by the word &"for"&. The
36786 addresses are listed after they have been qualified, but before any rewriting
36788 Recipients that were discarded by an ACL for MAIL or RCPT do not appear
36791 .cindex "log" "sender reception"
36792 &%received_sender%&: The unrewritten original sender of a message is added to
36793 the end of the log line that records the message's arrival, after the word
36794 &"from"& (before the recipients if &%received_recipients%& is also set).
36796 .cindex "log" "header lines for rejection"
36797 &%rejected_header%&: If a message's header has been received at the time a
36798 rejection is written to the reject log, the complete header is added to the
36799 log. Header logging can be turned off individually for messages that are
36800 rejected by the &[local_scan()]& function (see section &<<SECTapiforloc>>&).
36802 .cindex "log" "retry defer"
36803 &%retry_defer%&: A log line is written if a delivery is deferred because a
36804 retry time has not yet been reached. However, this &"retry time not reached"&
36805 message is always omitted from individual message logs after the first delivery
36808 .cindex "log" "return path"
36809 &%return_path_on_delivery%&: The return path that is being transmitted with
36810 the message is included in delivery and bounce lines, using the tag P=.
36811 This is omitted if no delivery actually happens, for example, if routing fails,
36812 or if delivery is to &_/dev/null_& or to &`:blackhole:`&.
36814 .cindex "log" "sender on delivery"
36815 &%sender_on_delivery%&: The message's sender address is added to every delivery
36816 and bounce line, tagged by F= (for &"from"&).
36817 This is the original sender that was received with the message; it is not
36818 necessarily the same as the outgoing return path.
36820 .cindex "log" "sender verify failure"
36821 &%sender_verify_fail%&: If this selector is unset, the separate log line that
36822 gives details of a sender verification failure is not written. Log lines for
36823 the rejection of SMTP commands contain just &"sender verify failed"&, so some
36826 .cindex "log" "size rejection"
36827 &%size_reject%&: A log line is written whenever a message is rejected because
36830 .cindex "log" "frozen messages; skipped"
36831 .cindex "frozen messages" "logging skipping"
36832 &%skip_delivery%&: A log line is written whenever a message is skipped during a
36833 queue run because it is frozen or because another process is already delivering
36835 .cindex "&""spool file is locked""&"
36836 The message that is written is &"spool file is locked"&.
36838 .cindex "log" "smtp confirmation"
36839 .cindex "SMTP" "logging confirmation"
36840 .cindex "LMTP" "logging confirmation"
36841 &%smtp_confirmation%&: The response to the final &"."& in the SMTP or LMTP dialogue for
36842 outgoing messages is added to delivery log lines in the form &`C=`&<&'text'&>.
36843 A number of MTAs (including Exim) return an identifying string in this
36846 .cindex "log" "SMTP connections"
36847 .cindex "SMTP" "logging connections"
36848 &%smtp_connection%&: A log line is written whenever an incoming SMTP connection is
36849 established or closed, unless the connection is from a host that matches
36850 &%hosts_connection_nolog%&. (In contrast, &%lost_incoming_connection%& applies
36851 only when the closure is unexpected.) This applies to connections from local
36852 processes that use &%-bs%& as well as to TCP/IP connections. If a connection is
36853 dropped in the middle of a message, a log line is always written, whether or
36854 not this selector is set, but otherwise nothing is written at the start and end
36855 of connections unless this selector is enabled.
36857 For TCP/IP connections to an Exim daemon, the current number of connections is
36858 included in the log message for each new connection, but note that the count is
36859 reset if the daemon is restarted.
36860 Also, because connections are closed (and the closure is logged) in
36861 subprocesses, the count may not include connections that have been closed but
36862 whose termination the daemon has not yet noticed. Thus, while it is possible to
36863 match up the opening and closing of connections in the log, the value of the
36864 logged counts may not be entirely accurate.
36866 .cindex "log" "SMTP transaction; incomplete"
36867 .cindex "SMTP" "logging incomplete transactions"
36868 &%smtp_incomplete_transaction%&: When a mail transaction is aborted by
36869 RSET, QUIT, loss of connection, or otherwise, the incident is logged,
36870 and the message sender plus any accepted recipients are included in the log
36871 line. This can provide evidence of dictionary attacks.
36873 .cindex "log" "non-MAIL SMTP sessions"
36874 .cindex "MAIL" "logging session without"
36875 &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP
36876 connection terminates without having issued a MAIL command. This includes both
36877 the case when the connection is dropped, and the case when QUIT is used. It
36878 does not include cases where the connection is rejected right at the start (by
36879 an ACL, or because there are too many connections, or whatever). These cases
36880 already have their own log lines.
36882 The log line that is written contains the identity of the client in the usual
36883 way, followed by D= and a time, which records the duration of the connection.
36884 If the connection was authenticated, this fact is logged exactly as it is for
36885 an incoming message, with an A= item. If the connection was encrypted, CV=,
36886 DN=, and X= items may appear as they do for an incoming message, controlled by
36887 the same logging options.
36889 Finally, if any SMTP commands were issued during the connection, a C= item
36890 is added to the line, listing the commands that were used. For example,
36894 shows that the client issued QUIT straight after EHLO. If there were fewer
36895 than 20 commands, they are all listed. If there were more than 20 commands,
36896 the last 20 are listed, preceded by &"..."&. However, with the default
36897 setting of 10 for &%smtp_accept_max_nonmail%&, the connection will in any case
36898 have been aborted before 20 non-mail commands are processed.
36900 &%smtp_mailauth%&: A third subfield with the authenticated sender,
36901 colon-separated, is appended to the A= item for a message arrival or delivery
36902 log line, if an AUTH argument to the SMTP MAIL command (see &<<SECTauthparamail>>&)
36903 was accepted or used.
36905 .cindex "log" "SMTP protocol error"
36906 .cindex "SMTP" "logging protocol error"
36907 &%smtp_protocol_error%&: A log line is written for every SMTP protocol error
36908 encountered. Exim does not have perfect detection of all protocol errors
36909 because of transmission delays and the use of pipelining. If PIPELINING has
36910 been advertised to a client, an Exim server assumes that the client will use
36911 it, and therefore it does not count &"expected"& errors (for example, RCPT
36912 received after rejecting MAIL) as protocol errors.
36914 .cindex "SMTP" "logging syntax errors"
36915 .cindex "SMTP" "syntax errors; logging"
36916 .cindex "SMTP" "unknown command; logging"
36917 .cindex "log" "unknown SMTP command"
36918 .cindex "log" "SMTP syntax error"
36919 &%smtp_syntax_error%&: A log line is written for every SMTP syntax error
36920 encountered. An unrecognized command is treated as a syntax error. For an
36921 external connection, the host identity is given; for an internal connection
36922 using &%-bs%& the sender identification (normally the calling user) is given.
36924 .cindex "log" "subject"
36925 .cindex "subject, logging"
36926 &%subject%&: The subject of the message is added to the arrival log line,
36927 preceded by &"T="& (T for &"topic"&, since S is already used for &"size"&).
36928 Any MIME &"words"& in the subject are decoded. The &%print_topbitchars%& option
36929 specifies whether characters with values greater than 127 should be logged
36930 unchanged, or whether they should be rendered as escape sequences.
36932 .cindex "log" "certificate verification"
36934 .cindex DANE logging
36935 &%tls_certificate_verified%&: An extra item is added to <= and => log lines
36936 when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
36938 using a CA trust anchor,
36939 &`CA=dane`& if using a DNS trust anchor,
36940 and &`CV=no`& if not.
36942 .cindex "log" "TLS cipher"
36943 .cindex "TLS" "logging cipher"
36944 &%tls_cipher%&: When a message is sent or received over an encrypted
36945 connection, the cipher suite used is added to the log line, preceded by X=.
36947 .cindex "log" "TLS peer DN"
36948 .cindex "TLS" "logging peer DN"
36949 &%tls_peerdn%&: When a message is sent or received over an encrypted
36950 connection, and a certificate is supplied by the remote host, the peer DN is
36951 added to the log line, preceded by DN=.
36953 .cindex "log" "TLS SNI"
36954 .cindex "TLS" "logging SNI"
36955 &%tls_sni%&: When a message is received over an encrypted connection, and
36956 the remote host provided the Server Name Indication extension, the SNI is
36957 added to the log line, preceded by SNI=.
36959 .cindex "log" "DNS failure in list"
36960 &%unknown_in_list%&: This setting causes a log entry to be written when the
36961 result of a list match is failure because a DNS lookup failed.
36965 .section "Message log" "SECID260"
36966 .cindex "message" "log file for"
36967 .cindex "log" "message log; description of"
36968 .cindex "&_msglog_& directory"
36969 .oindex "&%preserve_message_logs%&"
36970 In addition to the general log files, Exim writes a log file for each message
36971 that it handles. The names of these per-message logs are the message ids, and
36972 they are kept in the &_msglog_& sub-directory of the spool directory. Each
36973 message log contains copies of the log lines that apply to the message. This
36974 makes it easier to inspect the status of an individual message without having
36975 to search the main log. A message log is deleted when processing of the message
36976 is complete, unless &%preserve_message_logs%& is set, but this should be used
36977 only with great care because they can fill up your disk very quickly.
36979 On a heavily loaded system, it may be desirable to disable the use of
36980 per-message logs, in order to reduce disk I/O. This can be done by setting the
36981 &%message_logs%& option false.
36987 . ////////////////////////////////////////////////////////////////////////////
36988 . ////////////////////////////////////////////////////////////////////////////
36990 .chapter "Exim utilities" "CHAPutils"
36991 .scindex IIDutils "utilities"
36992 A number of utility scripts and programs are supplied with Exim and are
36993 described in this chapter. There is also the Exim Monitor, which is covered in
36994 the next chapter. The utilities described here are:
36996 .itable none 0 0 3 7* left 15* left 40* left
36997 .irow &<<SECTfinoutwha>>& &'exiwhat'& &&&
36998 "list what Exim processes are doing"
36999 .irow &<<SECTgreptheque>>& &'exiqgrep'& "grep the queue"
37000 .irow &<<SECTsumtheque>>& &'exiqsumm'& "summarize the queue"
37001 .irow &<<SECTextspeinf>>& &'exigrep'& "search the main log"
37002 .irow &<<SECTexipick>>& &'exipick'& "select messages on &&&
37004 .irow &<<SECTcyclogfil>>& &'exicyclog'& "cycle (rotate) log files"
37005 .irow &<<SECTmailstat>>& &'eximstats'& &&&
37006 "extract statistics from the log"
37007 .irow &<<SECTcheckaccess>>& &'exim_checkaccess'& &&&
37008 "check address acceptance from given IP"
37009 .irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
37010 .irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
37011 .irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
37012 .irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
37013 .irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
37014 .irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
37017 Another utility that might be of use to sites with many MTAs is Tom Kistner's
37018 &'exilog'&. It provides log visualizations across multiple Exim servers. See
37019 &url(http://duncanthrax.net/exilog/) for details.
37024 .section "Finding out what Exim processes are doing (exiwhat)" "SECTfinoutwha"
37025 .cindex "&'exiwhat'&"
37026 .cindex "process, querying"
37028 On operating systems that can restart a system call after receiving a signal
37029 (most modern OS), an Exim process responds to the SIGUSR1 signal by writing
37030 a line describing what it is doing to the file &_exim-process.info_& in the
37031 Exim spool directory. The &'exiwhat'& script sends the signal to all Exim
37032 processes it can find, having first emptied the file. It then waits for one
37033 second to allow the Exim processes to react before displaying the results. In
37034 order to run &'exiwhat'& successfully you have to have sufficient privilege to
37035 send the signal to the Exim processes, so it is normally run as root.
37037 &*Warning*&: This is not an efficient process. It is intended for occasional
37038 use by system administrators. It is not sensible, for example, to set up a
37039 script that sends SIGUSR1 signals to Exim processes at short intervals.
37042 Unfortunately, the &'ps'& command that &'exiwhat'& uses to find Exim processes
37043 varies in different operating systems. Not only are different options used,
37044 but the format of the output is different. For this reason, there are some
37045 system configuration options that configure exactly how &'exiwhat'& works. If
37046 it doesn't seem to be working for you, check the following compile-time
37049 &`EXIWHAT_PS_CMD `& the command for running &'ps'&
37050 &`EXIWHAT_PS_ARG `& the argument for &'ps'&
37051 &`EXIWHAT_EGREP_ARG `& the argument for &'egrep'& to select from &'ps'& output
37052 &`EXIWHAT_KILL_ARG `& the argument for the &'kill'& command
37054 An example of typical output from &'exiwhat'& is
37056 164 daemon: -q1h, listening on port 25
37057 10483 running queue: waiting for 0tAycK-0002ij-00 (10492)
37058 10492 delivering 0tAycK-0002ij-00 to mail.ref.example
37059 [10.19.42.42] (editor@ref.example)
37060 10592 handling incoming call from [192.168.243.242]
37061 10628 accepting a local non-SMTP message
37063 The first number in the output line is the process number. The third line has
37064 been split here, in order to fit it on the page.
37068 .section "Selective queue listing (exiqgrep)" "SECTgreptheque"
37069 .cindex "&'exiqgrep'&"
37070 .cindex "queue" "grepping"
37071 This utility is a Perl script contributed by Matt Hubbard. It runs
37075 or (in case &*-a*& switch is specified)
37079 The &*-C*& option is used to specify an alternate &_exim.conf_& which might
37080 contain alternate exim configuration the queue management might be using.
37082 to obtain a queue listing, and then greps the output to select messages
37083 that match given criteria. The following selection options are available:
37086 .vitem &*-f*&&~<&'regex'&>
37087 Match the sender address using a case-insensitive search. The field that is
37088 tested is enclosed in angle brackets, so you can test for bounce messages with
37092 .vitem &*-r*&&~<&'regex'&>
37093 Match a recipient address using a case-insensitive search. The field that is
37094 tested is not enclosed in angle brackets.
37096 .vitem &*-s*&&~<&'regex'&>
37097 Match against the size field.
37099 .vitem &*-y*&&~<&'seconds'&>
37100 Match messages that are younger than the given time.
37102 .vitem &*-o*&&~<&'seconds'&>
37103 Match messages that are older than the given time.
37106 Match only frozen messages.
37109 Match only non-frozen messages.
37112 The following options control the format of the output:
37116 Display only the count of matching messages.
37119 Long format &-- display the full message information as output by Exim. This is
37123 Display message ids only.
37126 Brief format &-- one line per message.
37129 Display messages in reverse order.
37132 Include delivered recipients in queue listing.
37135 There is one more option, &%-h%&, which outputs a list of options.
37139 .section "Summarizing the queue (exiqsumm)" "SECTsumtheque"
37140 .cindex "&'exiqsumm'&"
37141 .cindex "queue" "summary"
37142 The &'exiqsumm'& utility is a Perl script which reads the output of &`exim
37143 -bp`& and produces a summary of the messages on the queue. Thus, you use it by
37144 running a command such as
37146 exim -bp | exiqsumm
37148 The output consists of one line for each domain that has messages waiting for
37149 it, as in the following example:
37151 3 2322 74m 66m msn.com.example
37153 Each line lists the number of pending deliveries for a domain, their total
37154 volume, and the length of time that the oldest and the newest messages have
37155 been waiting. Note that the number of pending deliveries is greater than the
37156 number of messages when messages have more than one recipient.
37158 A summary line is output at the end. By default the output is sorted on the
37159 domain name, but &'exiqsumm'& has the options &%-a%& and &%-c%&, which cause
37160 the output to be sorted by oldest message and by count of messages,
37161 respectively. There are also three options that split the messages for each
37162 domain into two or more subcounts: &%-b%& separates bounce messages, &%-f%&
37163 separates frozen messages, and &%-s%& separates messages according to their
37166 The output of &'exim -bp'& contains the original addresses in the message, so
37167 this also applies to the output from &'exiqsumm'&. No domains from addresses
37168 generated by aliasing or forwarding are included (unless the &%one_time%&
37169 option of the &(redirect)& router has been used to convert them into &"top
37170 level"& addresses).
37175 .section "Extracting specific information from the log (exigrep)" &&&
37177 .cindex "&'exigrep'&"
37178 .cindex "log" "extracts; grepping for"
37179 The &'exigrep'& utility is a Perl script that searches one or more main log
37180 files for entries that match a given pattern. When it finds a match, it
37181 extracts all the log entries for the relevant message, not just those that
37182 match the pattern. Thus, &'exigrep'& can extract complete log entries for a
37183 given message, or all mail for a given user, or for a given host, for example.
37184 The input files can be in Exim log format or syslog format.
37185 If a matching log line is not associated with a specific message, it is
37186 included in &'exigrep'&'s output without any additional lines. The usage is:
37188 &`exigrep [-t<`&&'n'&&`>] [-I] [-l] [-M] [-v] <`&&'pattern'&&`> [<`&&'log file'&&`>] ...`&
37190 If no log file names are given on the command line, the standard input is read.
37192 The &%-t%& argument specifies a number of seconds. It adds an additional
37193 condition for message selection. Messages that are complete are shown only if
37194 they spent more than <&'n'&> seconds on the queue.
37196 By default, &'exigrep'& does case-insensitive matching. The &%-I%& option
37197 makes it case-sensitive. This may give a performance improvement when searching
37198 large log files. Without &%-I%&, the Perl pattern matches use Perl's &`/i`&
37199 option; with &%-I%& they do not. In both cases it is possible to change the
37200 case sensitivity within the pattern by using &`(?i)`& or &`(?-i)`&.
37202 The &%-l%& option means &"literal"&, that is, treat all characters in the
37203 pattern as standing for themselves. Otherwise the pattern must be a Perl
37204 regular expression.
37206 The &%-v%& option inverts the matching condition. That is, a line is selected
37207 if it does &'not'& match the pattern.
37209 The &%-M%& options means &"related messages"&. &'exigrep'& will show messages
37210 that are generated as a result/response to a message that &'exigrep'& matched
37214 user_a sends a message to user_b, which generates a bounce back to user_b. If
37215 &'exigrep'& is used to search for &"user_a"&, only the first message will be
37216 displayed. But if &'exigrep'& is used to search for &"user_b"&, the first and
37217 the second (bounce) message will be displayed. Using &%-M%& with &'exigrep'&
37218 when searching for &"user_a"& will show both messages since the bounce is
37219 &"related"& to or a &"result"& of the first message that was found by the
37222 If the location of a &'zcat'& command is known from the definition of
37223 ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file
37224 whose name ends in COMPRESS_SUFFIX through &'zcat'& as it searches it.
37225 If the ZCAT_COMMAND is not executable, &'exigrep'& tries to use
37226 autodetection of some well known compression extensions.
37229 .section "Selecting messages by various criteria (exipick)" "SECTexipick"
37230 .cindex "&'exipick'&"
37231 John Jetmore's &'exipick'& utility is included in the Exim distribution. It
37232 lists messages from the queue according to a variety of criteria. For details
37233 of &'exipick'&'s facilities, run &'exipick'& with
37234 the &%--help%& option.
37237 .section "Cycling log files (exicyclog)" "SECTcyclogfil"
37238 .cindex "log" "cycling local files"
37239 .cindex "cycling logs"
37240 .cindex "&'exicyclog'&"
37241 The &'exicyclog'& script can be used to cycle (rotate) &'mainlog'& and
37242 &'rejectlog'& files. This is not necessary if only syslog is being used, or if
37243 you are using log files with datestamps in their names (see section
37244 &<<SECTdatlogfil>>&). Some operating systems have their own standard mechanisms
37245 for log cycling, and these can be used instead of &'exicyclog'& if preferred.
37246 There are two command line options for &'exicyclog'&:
37248 &%-k%& <&'count'&> specifies the number of log files to keep, overriding the
37249 default that is set when Exim is built. The default default is 10.
37251 &%-l%& <&'path'&> specifies the log file path, in the same format as Exim's
37252 &%log_file_path%& option (for example, &`/var/log/exim_%slog`&), again
37253 overriding the script's default, which is to find the setting from Exim's
37257 Each time &'exicyclog'& is run the file names get &"shuffled down"& by one. If
37258 the main log file name is &_mainlog_& (the default) then when &'exicyclog'& is
37259 run &_mainlog_& becomes &_mainlog.01_&, the previous &_mainlog.01_& becomes
37260 &_mainlog.02_& and so on, up to the limit that is set in the script or by the
37261 &%-k%& option. Log files whose numbers exceed the limit are discarded. Reject
37262 logs are handled similarly.
37264 If the limit is greater than 99, the script uses 3-digit numbers such as
37265 &_mainlog.001_&, &_mainlog.002_&, etc. If you change from a number less than 99
37266 to one that is greater, or &'vice versa'&, you will have to fix the names of
37267 any existing log files.
37269 If no &_mainlog_& file exists, the script does nothing. Files that &"drop off"&
37270 the end are deleted. All files with numbers greater than 01 are compressed,
37271 using a compression command which is configured by the COMPRESS_COMMAND
37272 setting in &_Local/Makefile_&. It is usual to run &'exicyclog'& daily from a
37273 root &%crontab%& entry of the form
37275 1 0 * * * su exim -c /usr/exim/bin/exicyclog
37277 assuming you have used the name &"exim"& for the Exim user. You can run
37278 &'exicyclog'& as root if you wish, but there is no need.
37282 .section "Mail statistics (eximstats)" "SECTmailstat"
37283 .cindex "statistics"
37284 .cindex "&'eximstats'&"
37285 A Perl script called &'eximstats'& is provided for extracting statistical
37286 information from log files. The output is either plain text, or HTML.
37287 Exim log files are also supported by the &'Lire'& system produced by the
37288 LogReport Foundation &url(http://www.logreport.org).
37290 The &'eximstats'& script has been hacked about quite a bit over time. The
37291 latest version is the result of some extensive revision by Steve Campbell. A
37292 lot of information is given by default, but there are options for suppressing
37293 various parts of it. Following any options, the arguments to the script are a
37294 list of files, which should be main log files. For example:
37296 eximstats -nr /var/spool/exim/log/mainlog.01
37298 By default, &'eximstats'& extracts information about the number and volume of
37299 messages received from or delivered to various hosts. The information is sorted
37300 both by message count and by volume, and the top fifty hosts in each category
37301 are listed on the standard output. Similar information, based on email
37302 addresses or domains instead of hosts can be requested by means of various
37303 options. For messages delivered and received locally, similar statistics are
37304 also produced per user.
37306 The output also includes total counts and statistics about delivery errors, and
37307 histograms showing the number of messages received and deliveries made in each
37308 hour of the day. A delivery with more than one address in its envelope (for
37309 example, an SMTP transaction with more than one RCPT command) is counted
37310 as a single delivery by &'eximstats'&.
37312 Though normally more deliveries than receipts are reported (as messages may
37313 have multiple recipients), it is possible for &'eximstats'& to report more
37314 messages received than delivered, even though the queue is empty at the start
37315 and end of the period in question. If an incoming message contains no valid
37316 recipients, no deliveries are recorded for it. A bounce message is handled as
37317 an entirely separate message.
37319 &'eximstats'& always outputs a grand total summary giving the volume and number
37320 of messages received and deliveries made, and the number of hosts involved in
37321 each case. It also outputs the number of messages that were delayed (that is,
37322 not completely delivered at the first attempt), and the number that had at
37323 least one address that failed.
37325 The remainder of the output is in sections that can be independently disabled
37326 or modified by various options. It consists of a summary of deliveries by
37327 transport, histograms of messages received and delivered per time interval
37328 (default per hour), information about the time messages spent on the queue,
37329 a list of relayed messages, lists of the top fifty sending hosts, local
37330 senders, destination hosts, and destination local users by count and by volume,
37331 and a list of delivery errors that occurred.
37333 The relay information lists messages that were actually relayed, that is, they
37334 came from a remote host and were directly delivered to some other remote host,
37335 without being processed (for example, for aliasing or forwarding) locally.
37337 There are quite a few options for &'eximstats'& to control exactly what it
37338 outputs. These are documented in the Perl script itself, and can be extracted
37339 by running the command &(perldoc)& on the script. For example:
37341 perldoc /usr/exim/bin/eximstats
37344 .section "Checking access policy (exim_checkaccess)" "SECTcheckaccess"
37345 .cindex "&'exim_checkaccess'&"
37346 .cindex "policy control" "checking access"
37347 .cindex "checking access"
37348 The &%-bh%& command line argument allows you to run a fake SMTP session with
37349 debugging output, in order to check what Exim is doing when it is applying
37350 policy controls to incoming SMTP mail. However, not everybody is sufficiently
37351 familiar with the SMTP protocol to be able to make full use of &%-bh%&, and
37352 sometimes you just want to answer the question &"Does this address have
37353 access?"& without bothering with any further details.
37355 The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%&. It takes
37356 two arguments, an IP address and an email address:
37358 exim_checkaccess 10.9.8.7 A.User@a.domain.example
37360 The utility runs a call to Exim with the &%-bh%& option, to test whether the
37361 given email address would be accepted in a RCPT command in a TCP/IP
37362 connection from the host with the given IP address. The output of the utility
37363 is either the word &"accepted"&, or the SMTP error response, for example:
37366 550 Relay not permitted
37368 When running this test, the utility uses &`<>`& as the envelope sender address
37369 for the MAIL command, but you can change this by providing additional
37370 options. These are passed directly to the Exim command. For example, to specify
37371 that the test is to be run with the sender address &'himself@there.example'&
37374 exim_checkaccess 10.9.8.7 A.User@a.domain.example \
37375 -f himself@there.example
37377 Note that these additional Exim command line items must be given after the two
37378 mandatory arguments.
37380 Because the &%exim_checkaccess%& uses &%-bh%&, it does not perform callouts
37381 while running its checks. You can run checks that include callouts by using
37382 &%-bhc%&, but this is not yet available in a &"packaged"& form.
37386 .section "Making DBM files (exim_dbmbuild)" "SECTdbmbuild"
37387 .cindex "DBM" "building dbm files"
37388 .cindex "building DBM files"
37389 .cindex "&'exim_dbmbuild'&"
37390 .cindex "lower casing"
37391 .cindex "binary zero" "in lookup key"
37392 The &'exim_dbmbuild'& program reads an input file containing keys and data in
37393 the format used by the &(lsearch)& lookup (see section
37394 &<<SECTsinglekeylookups>>&). It writes a DBM file using the lower-cased alias
37395 names as keys and the remainder of the information as data. The lower-casing
37396 can be prevented by calling the program with the &%-nolc%& option.
37398 A terminating zero is included as part of the key string. This is expected by
37399 the &(dbm)& lookup type. However, if the option &%-nozero%& is given,
37400 &'exim_dbmbuild'& creates files without terminating zeroes in either the key
37401 strings or the data strings. The &(dbmnz)& lookup type can be used with such
37404 The program requires two arguments: the name of the input file (which can be a
37405 single hyphen to indicate the standard input), and the name of the output file.
37406 It creates the output under a temporary name, and then renames it if all went
37410 If the native DB interface is in use (USE_DB is set in a compile-time
37411 configuration file &-- this is common in free versions of Unix) the two file
37412 names must be different, because in this mode the Berkeley DB functions create
37413 a single output file using exactly the name given. For example,
37415 exim_dbmbuild /etc/aliases /etc/aliases.db
37417 reads the system alias file and creates a DBM version of it in
37418 &_/etc/aliases.db_&.
37420 In systems that use the &'ndbm'& routines (mostly proprietary versions of
37421 Unix), two files are used, with the suffixes &_.dir_& and &_.pag_&. In this
37422 environment, the suffixes are added to the second argument of
37423 &'exim_dbmbuild'&, so it can be the same as the first. This is also the case
37424 when the Berkeley functions are used in compatibility mode (though this is not
37425 recommended), because in that case it adds a &_.db_& suffix to the file name.
37427 If a duplicate key is encountered, the program outputs a warning, and when it
37428 finishes, its return code is 1 rather than zero, unless the &%-noduperr%&
37429 option is used. By default, only the first of a set of duplicates is used &--
37430 this makes it compatible with &(lsearch)& lookups. There is an option
37431 &%-lastdup%& which causes it to use the data for the last duplicate instead.
37432 There is also an option &%-nowarn%&, which stops it listing duplicate keys to
37433 &%stderr%&. For other errors, where it doesn't actually make a new file, the
37439 .section "Finding individual retry times (exinext)" "SECTfinindret"
37440 .cindex "retry" "times"
37441 .cindex "&'exinext'&"
37442 A utility called &'exinext'& (mostly a Perl script) provides the ability to
37443 fish specific information out of the retry database. Given a mail domain (or a
37444 complete address), it looks up the hosts for that domain, and outputs any retry
37445 information for the hosts or for the domain. At present, the retry information
37446 is obtained by running &'exim_dumpdb'& (see below) and post-processing the
37447 output. For example:
37449 $ exinext piglet@milne.fict.example
37450 kanga.milne.example:192.168.8.1 error 146: Connection refused
37451 first failed: 21-Feb-1996 14:57:34
37452 last tried: 21-Feb-1996 14:57:34
37453 next try at: 21-Feb-1996 15:02:34
37454 roo.milne.example:192.168.8.3 error 146: Connection refused
37455 first failed: 20-Jan-1996 13:12:08
37456 last tried: 21-Feb-1996 11:42:03
37457 next try at: 21-Feb-1996 19:42:03
37458 past final cutoff time
37460 You can also give &'exinext'& a local part, without a domain, and it
37461 will give any retry information for that local part in your default domain.
37462 A message id can be used to obtain retry information pertaining to a specific
37463 message. This exists only when an attempt to deliver a message to a remote host
37464 suffers a message-specific error (see section &<<SECToutSMTPerr>>&).
37465 &'exinext'& is not particularly efficient, but then it is not expected to be
37468 The &'exinext'& utility calls Exim to find out information such as the location
37469 of the spool directory. The utility has &%-C%& and &%-D%& options, which are
37470 passed on to the &'exim'& commands. The first specifies an alternate Exim
37471 configuration file, and the second sets macros for use within the configuration
37472 file. These features are mainly to help in testing, but might also be useful in
37473 environments where more than one configuration file is in use.
37477 .section "Hints database maintenance" "SECThindatmai"
37478 .cindex "hints database" "maintenance"
37479 .cindex "maintaining Exim's hints database"
37480 Three utility programs are provided for maintaining the DBM files that Exim
37481 uses to contain its delivery hint information. Each program requires two
37482 arguments. The first specifies the name of Exim's spool directory, and the
37483 second is the name of the database it is to operate on. These are as follows:
37486 &'retry'&: the database of retry information
37488 &'wait-'&<&'transport name'&>: databases of information about messages waiting
37491 &'callout'&: the callout cache
37493 &'ratelimit'&: the data for implementing the ratelimit ACL condition
37495 &'misc'&: other hints data
37498 The &'misc'& database is used for
37501 Serializing ETRN runs (when &%smtp_etrn_serialize%& is set)
37503 Serializing delivery to a specific host (when &%serialize_hosts%& is set in an
37504 &(smtp)& transport)
37506 Limiting the concurrency of specific transports (when &%max_parallel%& is set
37512 .section "exim_dumpdb" "SECID261"
37513 .cindex "&'exim_dumpdb'&"
37514 The entire contents of a database are written to the standard output by the
37515 &'exim_dumpdb'& program, which has no options or arguments other than the
37516 spool and database names. For example, to dump the retry database:
37518 exim_dumpdb /var/spool/exim retry
37520 Two lines of output are produced for each entry:
37522 T:mail.ref.example:192.168.242.242 146 77 Connection refused
37523 31-Oct-1995 12:00:12 02-Nov-1995 12:21:39 02-Nov-1995 20:21:39 *
37525 The first item on the first line is the key of the record. It starts with one
37526 of the letters R, or T, depending on whether it refers to a routing or
37527 transport retry. For a local delivery, the next part is the local address; for
37528 a remote delivery it is the name of the remote host, followed by its failing IP
37529 address (unless &%retry_include_ip_address%& is set false on the &(smtp)&
37530 transport). If the remote port is not the standard one (port 25), it is added
37531 to the IP address. Then there follows an error code, an additional error code,
37532 and a textual description of the error.
37534 The three times on the second line are the time of first failure, the time of
37535 the last delivery attempt, and the computed time for the next attempt. The line
37536 ends with an asterisk if the cutoff time for the last retry rule has been
37539 Each output line from &'exim_dumpdb'& for the &'wait-xxx'& databases
37540 consists of a host name followed by a list of ids for messages that are or were
37541 waiting to be delivered to that host. If there are a very large number for any
37542 one host, continuation records, with a sequence number added to the host name,
37543 may be seen. The data in these records is often out of date, because a message
37544 may be routed to several alternative hosts, and Exim makes no effort to keep
37549 .section "exim_tidydb" "SECID262"
37550 .cindex "&'exim_tidydb'&"
37551 The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
37552 database. If run with no options, it removes all records that are more than 30
37553 days old. The age is calculated from the date and time that the record was last
37554 updated. Note that, in the case of the retry database, it is &'not'& the time
37555 since the first delivery failure. Information about a host that has been down
37556 for more than 30 days will remain in the database, provided that the record is
37557 updated sufficiently often.
37559 The cutoff date can be altered by means of the &%-t%& option, which must be
37560 followed by a time. For example, to remove all records older than a week from
37561 the retry database:
37563 exim_tidydb -t 7d /var/spool/exim retry
37565 Both the &'wait-xxx'& and &'retry'& databases contain items that involve
37566 message ids. In the former these appear as data in records keyed by host &--
37567 they were messages that were waiting for that host &-- and in the latter they
37568 are the keys for retry information for messages that have suffered certain
37569 types of error. When &'exim_tidydb'& is run, a check is made to ensure that
37570 message ids in database records are those of messages that are still on the
37571 queue. Message ids for messages that no longer exist are removed from
37572 &'wait-xxx'& records, and if this leaves any records empty, they are deleted.
37573 For the &'retry'& database, records whose keys are non-existent message ids are
37574 removed. The &'exim_tidydb'& utility outputs comments on the standard output
37575 whenever it removes information from the database.
37577 Certain records are automatically removed by Exim when they are no longer
37578 needed, but others are not. For example, if all the MX hosts for a domain are
37579 down, a retry record is created for each one. If the primary MX host comes back
37580 first, its record is removed when Exim successfully delivers to it, but the
37581 records for the others remain because Exim has not tried to use those hosts.
37583 It is important, therefore, to run &'exim_tidydb'& periodically on all the
37584 hints databases. You should do this at a quiet time of day, because it requires
37585 a database to be locked (and therefore inaccessible to Exim) while it does its
37586 work. Removing records from a DBM file does not normally make the file smaller,
37587 but all the common DBM libraries are able to re-use the space that is released.
37588 After an initial phase of increasing in size, the databases normally reach a
37589 point at which they no longer get any bigger, as long as they are regularly
37592 &*Warning*&: If you never run &'exim_tidydb'&, the space used by the hints
37593 databases is likely to keep on increasing.
37598 .section "exim_fixdb" "SECID263"
37599 .cindex "&'exim_fixdb'&"
37600 The &'exim_fixdb'& program is a utility for interactively modifying databases.
37601 Its main use is for testing Exim, but it might also be occasionally useful for
37602 getting round problems in a live system. It has no options, and its interface
37603 is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
37604 key of a database record can then be entered, and the data for that record is
37607 If &"d"& is typed at the next prompt, the entire record is deleted. For all
37608 except the &'retry'& database, that is the only operation that can be carried
37609 out. For the &'retry'& database, each field is output preceded by a number, and
37610 data for individual fields can be changed by typing the field number followed
37611 by new data, for example:
37615 resets the time of the next delivery attempt. Time values are given as a
37616 sequence of digit pairs for year, month, day, hour, and minute. Colons can be
37617 used as optional separators.
37622 .section "Mailbox maintenance (exim_lock)" "SECTmailboxmaint"
37623 .cindex "mailbox" "maintenance"
37624 .cindex "&'exim_lock'&"
37625 .cindex "locking mailboxes"
37626 The &'exim_lock'& utility locks a mailbox file using the same algorithm as
37627 Exim. For a discussion of locking issues, see section &<<SECTopappend>>&.
37628 &'Exim_lock'& can be used to prevent any modification of a mailbox by Exim or
37629 a user agent while investigating a problem. The utility requires the name of
37630 the file as its first argument. If the locking is successful, the second
37631 argument is run as a command (using C's &[system()]& function); if there is no
37632 second argument, the value of the SHELL environment variable is used; if this
37633 is unset or empty, &_/bin/sh_& is run. When the command finishes, the mailbox
37634 is unlocked and the utility ends. The following options are available:
37638 Use &[fcntl()]& locking on the open mailbox.
37641 Use &[flock()]& locking on the open mailbox, provided the operating system
37644 .vitem &%-interval%&
37645 This must be followed by a number, which is a number of seconds; it sets the
37646 interval to sleep between retries (default 3).
37648 .vitem &%-lockfile%&
37649 Create a lock file before opening the mailbox.
37652 Lock the mailbox using MBX rules.
37655 Suppress verification output.
37657 .vitem &%-retries%&
37658 This must be followed by a number; it sets the number of times to try to get
37659 the lock (default 10).
37661 .vitem &%-restore_time%&
37662 This option causes &%exim_lock%& to restore the modified and read times to the
37663 locked file before exiting. This allows you to access a locked mailbox (for
37664 example, to take a backup copy) without disturbing the times that the user
37667 .vitem &%-timeout%&
37668 This must be followed by a number, which is a number of seconds; it sets a
37669 timeout to be used with a blocking &[fcntl()]& lock. If it is not set (the
37670 default), a non-blocking call is used.
37673 Generate verbose output.
37676 If none of &%-fcntl%&, &%-flock%&, &%-lockfile%& or &%-mbx%& are given, the
37677 default is to create a lock file and also to use &[fcntl()]& locking on the
37678 mailbox, which is the same as Exim's default. The use of &%-flock%& or
37679 &%-fcntl%& requires that the file be writeable; the use of &%-lockfile%&
37680 requires that the directory containing the file be writeable. Locking by lock
37681 file does not last for ever; Exim assumes that a lock file is expired if it is
37682 more than 30 minutes old.
37684 The &%-mbx%& option can be used with either or both of &%-fcntl%& or
37685 &%-flock%&. It assumes &%-fcntl%& by default. MBX locking causes a shared lock
37686 to be taken out on the open mailbox, and an exclusive lock on the file
37687 &_/tmp/.n.m_& where &'n'& and &'m'& are the device number and inode
37688 number of the mailbox file. When the locking is released, if an exclusive lock
37689 can be obtained for the mailbox, the file in &_/tmp_& is deleted.
37691 The default output contains verification of the locking that takes place. The
37692 &%-v%& option causes some additional information to be given. The &%-q%& option
37693 suppresses all output except error messages.
37697 exim_lock /var/spool/mail/spqr
37699 runs an interactive shell while the file is locked, whereas
37701 &`exim_lock -q /var/spool/mail/spqr <<End`&
37702 <&'some commands'&>
37705 runs a specific non-interactive sequence of commands while the file is locked,
37706 suppressing all verification output. A single command can be run by a command
37709 exim_lock -q /var/spool/mail/spqr \
37710 "cp /var/spool/mail/spqr /some/where"
37712 Note that if a command is supplied, it must be entirely contained within the
37713 second argument &-- hence the quotes.
37717 . ////////////////////////////////////////////////////////////////////////////
37718 . ////////////////////////////////////////////////////////////////////////////
37720 .chapter "The Exim monitor" "CHAPeximon"
37721 .scindex IIDeximon "Exim monitor" "description"
37722 .cindex "X-windows"
37723 .cindex "&'eximon'&"
37724 .cindex "Local/eximon.conf"
37725 .cindex "&_exim_monitor/EDITME_&"
37726 The Exim monitor is an application which displays in an X window information
37727 about the state of Exim's queue and what Exim is doing. An admin user can
37728 perform certain operations on messages from this GUI interface; however all
37729 such facilities are also available from the command line, and indeed, the
37730 monitor itself makes use of the command line to perform any actions requested.
37734 .section "Running the monitor" "SECID264"
37735 The monitor is started by running the script called &'eximon'&. This is a shell
37736 script that sets up a number of environment variables, and then runs the
37737 binary called &_eximon.bin_&. The default appearance of the monitor window can
37738 be changed by editing the &_Local/eximon.conf_& file created by editing
37739 &_exim_monitor/EDITME_&. Comments in that file describe what the various
37740 parameters are for.
37742 The parameters that get built into the &'eximon'& script can be overridden for
37743 a particular invocation by setting up environment variables of the same names,
37744 preceded by &`EXIMON_`&. For example, a shell command such as
37746 EXIMON_LOG_DEPTH=400 eximon
37748 (in a Bourne-compatible shell) runs &'eximon'& with an overriding setting of
37749 the LOG_DEPTH parameter. If EXIMON_LOG_FILE_PATH is set in the environment, it
37750 overrides the Exim log file configuration. This makes it possible to have
37751 &'eximon'& tailing log data that is written to syslog, provided that MAIL.INFO
37752 syslog messages are routed to a file on the local host.
37754 X resources can be used to change the appearance of the window in the normal
37755 way. For example, a resource setting of the form
37757 Eximon*background: gray94
37759 changes the colour of the background to light grey rather than white. The
37760 stripcharts are drawn with both the data lines and the reference lines in
37761 black. This means that the reference lines are not visible when on top of the
37762 data. However, their colour can be changed by setting a resource called
37763 &"highlight"& (an odd name, but that's what the Athena stripchart widget uses).
37764 For example, if your X server is running Unix, you could set up lighter
37765 reference lines in the stripcharts by obeying
37768 Eximon*highlight: gray
37771 .cindex "admin user"
37772 In order to see the contents of messages on the queue, and to operate on them,
37773 &'eximon'& must either be run as root or by an admin user.
37775 The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may
37776 contain X11 resource parameters interpreted by the X11 library. In addition,
37777 if the first parameter starts with the string "gdb" then it is removed and the
37778 binary is invoked under gdb (the parameter is used as the gdb command-name, so
37779 versioned variants of gdb can be invoked).
37781 The monitor's window is divided into three parts. The first contains one or
37782 more stripcharts and two action buttons, the second contains a &"tail"& of the
37783 main log file, and the third is a display of the queue of messages awaiting
37784 delivery, with two more action buttons. The following sections describe these
37785 different parts of the display.
37790 .section "The stripcharts" "SECID265"
37791 .cindex "stripchart"
37792 The first stripchart is always a count of messages on the queue. Its name can
37793 be configured by setting QUEUE_STRIPCHART_NAME in the
37794 &_Local/eximon.conf_& file. The remaining stripcharts are defined in the
37795 configuration script by regular expression matches on log file entries, making
37796 it possible to display, for example, counts of messages delivered to certain
37797 hosts or using certain transports. The supplied defaults display counts of
37798 received and delivered messages, and of local and SMTP deliveries. The default
37799 period between stripchart updates is one minute; this can be adjusted by a
37800 parameter in the &_Local/eximon.conf_& file.
37802 The stripchart displays rescale themselves automatically as the value they are
37803 displaying changes. There are always 10 horizontal lines in each chart; the
37804 title string indicates the value of each division when it is greater than one.
37805 For example, &"x2"& means that each division represents a value of 2.
37807 It is also possible to have a stripchart which shows the percentage fullness of
37808 a particular disk partition, which is useful when local deliveries are confined
37809 to a single partition.
37811 .cindex "&%statvfs%& function"
37812 This relies on the availability of the &[statvfs()]& function or equivalent in
37813 the operating system. Most, but not all versions of Unix that support Exim have
37814 this. For this particular stripchart, the top of the chart always represents
37815 100%, and the scale is given as &"x10%"&. This chart is configured by setting
37816 SIZE_STRIPCHART and (optionally) SIZE_STRIPCHART_NAME in the
37817 &_Local/eximon.conf_& file.
37822 .section "Main action buttons" "SECID266"
37823 .cindex "size" "of monitor window"
37824 .cindex "Exim monitor" "window size"
37825 .cindex "window size"
37826 Below the stripcharts there is an action button for quitting the monitor. Next
37827 to this is another button marked &"Size"&. They are placed here so that
37828 shrinking the window to its default minimum size leaves just the queue count
37829 stripchart and these two buttons visible. Pressing the &"Size"& button causes
37830 the window to expand to its maximum size, unless it is already at the maximum,
37831 in which case it is reduced to its minimum.
37833 When expanding to the maximum, if the window cannot be fully seen where it
37834 currently is, it is moved back to where it was the last time it was at full
37835 size. When it is expanding from its minimum size, the old position is
37836 remembered, and next time it is reduced to the minimum it is moved back there.
37838 The idea is that you can keep a reduced window just showing one or two
37839 stripcharts at a convenient place on your screen, easily expand it to show
37840 the full window when required, and just as easily put it back to what it was.
37841 The idea is copied from what the &'twm'& window manager does for its
37842 &'f.fullzoom'& action. The minimum size of the window can be changed by setting
37843 the MIN_HEIGHT and MIN_WIDTH values in &_Local/eximon.conf_&.
37845 Normally, the monitor starts up with the window at its full size, but it can be
37846 built so that it starts up with the window at its smallest size, by setting
37847 START_SMALL=yes in &_Local/eximon.conf_&.
37851 .section "The log display" "SECID267"
37852 .cindex "log" "tail of; in monitor"
37853 The second section of the window is an area in which a display of the tail of
37854 the main log is maintained.
37855 To save space on the screen, the timestamp on each log line is shortened by
37856 removing the date and, if &%log_timezone%& is set, the timezone.
37857 The log tail is not available when the only destination for logging data is
37858 syslog, unless the syslog lines are routed to a local file whose name is passed
37859 to &'eximon'& via the EXIMON_LOG_FILE_PATH environment variable.
37861 The log sub-window has a scroll bar at its lefthand side which can be used to
37862 move back to look at earlier text, and the up and down arrow keys also have a
37863 scrolling effect. The amount of log that is kept depends on the setting of
37864 LOG_BUFFER in &_Local/eximon.conf_&, which specifies the amount of memory
37865 to use. When this is full, the earlier 50% of data is discarded &-- this is
37866 much more efficient than throwing it away line by line. The sub-window also has
37867 a horizontal scroll bar for accessing the ends of long log lines. This is the
37868 only means of horizontal scrolling; the right and left arrow keys are not
37869 available. Text can be cut from this part of the window using the mouse in the
37870 normal way. The size of this subwindow is controlled by parameters in the
37871 configuration file &_Local/eximon.conf_&.
37873 Searches of the text in the log window can be carried out by means of the ^R
37874 and ^S keystrokes, which default to a reverse and a forward search,
37875 respectively. The search covers only the text that is displayed in the window.
37876 It cannot go further back up the log.
37878 The point from which the search starts is indicated by a caret marker. This is
37879 normally at the end of the text in the window, but can be positioned explicitly
37880 by pointing and clicking with the left mouse button, and is moved automatically
37881 by a successful search. If new text arrives in the window when it is scrolled
37882 back, the caret remains where it is, but if the window is not scrolled back,
37883 the caret is moved to the end of the new text.
37885 Pressing ^R or ^S pops up a window into which the search text can be typed.
37886 There are buttons for selecting forward or reverse searching, for carrying out
37887 the search, and for cancelling. If the &"Search"& button is pressed, the search
37888 happens and the window remains so that further searches can be done. If the
37889 &"Return"& key is pressed, a single search is done and the window is closed. If
37890 ^C is typed the search is cancelled.
37892 The searching facility is implemented using the facilities of the Athena text
37893 widget. By default this pops up a window containing both &"search"& and
37894 &"replace"& options. In order to suppress the unwanted &"replace"& portion for
37895 eximon, a modified version of the &%TextPop%& widget is distributed with Exim.
37896 However, the linkers in BSDI and HP-UX seem unable to handle an externally
37897 provided version of &%TextPop%& when the remaining parts of the text widget
37898 come from the standard libraries. The compile-time option EXIMON_TEXTPOP can be
37899 unset to cut out the modified &%TextPop%&, making it possible to build Eximon
37900 on these systems, at the expense of having unwanted items in the search popup
37905 .section "The queue display" "SECID268"
37906 .cindex "queue" "display in monitor"
37907 The bottom section of the monitor window contains a list of all messages that
37908 are on the queue, which includes those currently being received or delivered,
37909 as well as those awaiting delivery. The size of this subwindow is controlled by
37910 parameters in the configuration file &_Local/eximon.conf_&, and the frequency
37911 at which it is updated is controlled by another parameter in the same file &--
37912 the default is 5 minutes, since queue scans can be quite expensive. However,
37913 there is an &"Update"& action button just above the display which can be used
37914 to force an update of the queue display at any time.
37916 When a host is down for some time, a lot of pending mail can build up for it,
37917 and this can make it hard to deal with other messages on the queue. To help
37918 with this situation there is a button next to &"Update"& called &"Hide"&. If
37919 pressed, a dialogue box called &"Hide addresses ending with"& is put up. If you
37920 type anything in here and press &"Return"&, the text is added to a chain of
37921 such texts, and if every undelivered address in a message matches at least one
37922 of the texts, the message is not displayed.
37924 If there is an address that does not match any of the texts, all the addresses
37925 are displayed as normal. The matching happens on the ends of addresses so, for
37926 example, &'cam.ac.uk'& specifies all addresses in Cambridge, while
37927 &'xxx@foo.com.example'& specifies just one specific address. When any hiding
37928 has been set up, a button called &"Unhide"& is displayed. If pressed, it
37929 cancels all hiding. Also, to ensure that hidden messages do not get forgotten,
37930 a hide request is automatically cancelled after one hour.
37932 While the dialogue box is displayed, you can't press any buttons or do anything
37933 else to the monitor window. For this reason, if you want to cut text from the
37934 queue display to use in the dialogue box, you have to do the cutting before
37935 pressing the &"Hide"& button.
37937 The queue display contains, for each unhidden queued message, the length of
37938 time it has been on the queue, the size of the message, the message id, the
37939 message sender, and the first undelivered recipient, all on one line. If it is
37940 a bounce message, the sender is shown as &"<>"&. If there is more than one
37941 recipient to which the message has not yet been delivered, subsequent ones are
37942 listed on additional lines, up to a maximum configured number, following which
37943 an ellipsis is displayed. Recipients that have already received the message are
37946 .cindex "frozen messages" "display"
37947 If a message is frozen, an asterisk is displayed at the left-hand side.
37949 The queue display has a vertical scroll bar, and can also be scrolled by means
37950 of the arrow keys. Text can be cut from it using the mouse in the normal way.
37951 The text searching facilities, as described above for the log window, are also
37952 available, but the caret is always moved to the end of the text when the queue
37953 display is updated.
37957 .section "The queue menu" "SECID269"
37958 .cindex "queue" "menu in monitor"
37959 If the &%shift%& key is held down and the left button is clicked when the mouse
37960 pointer is over the text for any message, an action menu pops up, and the first
37961 line of the queue display for the message is highlighted. This does not affect
37964 If you want to use some other event for popping up the menu, you can set the
37965 MENU_EVENT parameter in &_Local/eximon.conf_& to change the default, or
37966 set EXIMON_MENU_EVENT in the environment before starting the monitor. The
37967 value set in this parameter is a standard X event description. For example, to
37968 run eximon using &%ctrl%& rather than &%shift%& you could use
37970 EXIMON_MENU_EVENT='Ctrl<Btn1Down>' eximon
37972 The title of the menu is the message id, and it contains entries which act as
37976 &'message log'&: The contents of the message log for the message are displayed
37977 in a new text window.
37979 &'headers'&: Information from the spool file that contains the envelope
37980 information and headers is displayed in a new text window. See chapter
37981 &<<CHAPspool>>& for a description of the format of spool files.
37983 &'body'&: The contents of the spool file containing the body of the message are
37984 displayed in a new text window. There is a default limit of 20,000 bytes to the
37985 amount of data displayed. This can be changed by setting the BODY_MAX
37986 option at compile time, or the EXIMON_BODY_MAX option at run time.
37988 &'deliver message'&: A call to Exim is made using the &%-M%& option to request
37989 delivery of the message. This causes an automatic thaw if the message is
37990 frozen. The &%-v%& option is also set, and the output from Exim is displayed in
37991 a new text window. The delivery is run in a separate process, to avoid holding
37992 up the monitor while the delivery proceeds.
37994 &'freeze message'&: A call to Exim is made using the &%-Mf%& option to request
37995 that the message be frozen.
37997 .cindex "thawing messages"
37998 .cindex "unfreezing messages"
37999 .cindex "frozen messages" "thawing"
38000 &'thaw message'&: A call to Exim is made using the &%-Mt%& option to request
38001 that the message be thawed.
38003 .cindex "delivery" "forcing failure"
38004 &'give up on msg'&: A call to Exim is made using the &%-Mg%& option to request
38005 that Exim gives up trying to deliver the message. A bounce message is generated
38006 for any remaining undelivered addresses.
38008 &'remove message'&: A call to Exim is made using the &%-Mrm%& option to request
38009 that the message be deleted from the system without generating a bounce
38012 &'add recipient'&: A dialog box is displayed into which a recipient address can
38013 be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
38014 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
38015 Otherwise it must be entered as a fully qualified address. Pressing RETURN
38016 causes a call to Exim to be made using the &%-Mar%& option to request that an
38017 additional recipient be added to the message, unless the entry box is empty, in
38018 which case no action is taken.
38020 &'mark delivered'&: A dialog box is displayed into which a recipient address
38021 can be typed. If the address is not qualified and the QUALIFY_DOMAIN parameter
38022 is set in &_Local/eximon.conf_&, the address is qualified with that domain.
38023 Otherwise it must be entered as a fully qualified address. Pressing RETURN
38024 causes a call to Exim to be made using the &%-Mmd%& option to mark the given
38025 recipient address as already delivered, unless the entry box is empty, in which
38026 case no action is taken.
38028 &'mark all delivered'&: A call to Exim is made using the &%-Mmad%& option to
38029 mark all recipient addresses as already delivered.
38031 &'edit sender'&: A dialog box is displayed initialized with the current
38032 sender's address. Pressing RETURN causes a call to Exim to be made using the
38033 &%-Mes%& option to replace the sender address, unless the entry box is empty,
38034 in which case no action is taken. If you want to set an empty sender (as in
38035 bounce messages), you must specify it as &"<>"&. Otherwise, if the address is
38036 not qualified and the QUALIFY_DOMAIN parameter is set in &_Local/eximon.conf_&,
38037 the address is qualified with that domain.
38040 When a delivery is forced, a window showing the &%-v%& output is displayed. In
38041 other cases when a call to Exim is made, if there is any output from Exim (in
38042 particular, if the command fails) a window containing the command and the
38043 output is displayed. Otherwise, the results of the action are normally apparent
38044 from the log and queue displays. However, if you set ACTION_OUTPUT=yes in
38045 &_Local/eximon.conf_&, a window showing the Exim command is always opened, even
38046 if no output is generated.
38048 The queue display is automatically updated for actions such as freezing and
38049 thawing, unless ACTION_QUEUE_UPDATE=no has been set in
38050 &_Local/eximon.conf_&. In this case the &"Update"& button has to be used to
38051 force an update of the display after one of these actions.
38053 In any text window that is displayed as result of a menu action, the normal
38054 cut-and-paste facility is available, and searching can be carried out using ^R
38055 and ^S, as described above for the log tail window.
38062 . ////////////////////////////////////////////////////////////////////////////
38063 . ////////////////////////////////////////////////////////////////////////////
38065 .chapter "Security considerations" "CHAPsecurity"
38066 .scindex IIDsecurcon "security" "discussion of"
38067 This chapter discusses a number of issues concerned with security, some of
38068 which are also covered in other parts of this manual.
38070 For reasons that this author does not understand, some people have promoted
38071 Exim as a &"particularly secure"& mailer. Perhaps it is because of the
38072 existence of this chapter in the documentation. However, the intent of the
38073 chapter is simply to describe the way Exim works in relation to certain
38074 security concerns, not to make any specific claims about the effectiveness of
38075 its security as compared with other MTAs.
38077 What follows is a description of the way Exim is supposed to be. Best efforts
38078 have been made to try to ensure that the code agrees with the theory, but an
38079 absence of bugs can never be guaranteed. Any that are reported will get fixed
38080 as soon as possible.
38083 .section "Building a more &""hardened""& Exim" "SECID286"
38084 .cindex "security" "build-time features"
38085 There are a number of build-time options that can be set in &_Local/Makefile_&
38086 to create Exim binaries that are &"harder"& to attack, in particular by a rogue
38087 Exim administrator who does not have the root password, or by someone who has
38088 penetrated the Exim (but not the root) account. These options are as follows:
38091 ALT_CONFIG_PREFIX can be set to a string that is required to match the
38092 start of any file names used with the &%-C%& option. When it is set, these file
38093 names are also not allowed to contain the sequence &"/../"&. (However, if the
38094 value of the &%-C%& option is identical to the value of CONFIGURE_FILE in
38095 &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no
38096 default setting for &%ALT_CONFIG_PREFIX%&.
38098 If the permitted configuration files are confined to a directory to
38099 which only root has access, this guards against someone who has broken
38100 into the Exim account from running a privileged Exim with an arbitrary
38101 configuration file, and using it to break into other accounts.
38104 If a non-trusted configuration file (i.e. not the default configuration file
38105 or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST
38106 file) is specified with &%-C%&, or if macros are given with &%-D%& (but see
38107 the next item), then root privilege is retained only if the caller of Exim is
38108 root. This locks out the possibility of testing a configuration using &%-C%&
38109 right through message reception and delivery, even if the caller is root. The
38110 reception works, but by that time, Exim is running as the Exim user, so when
38111 it re-execs to regain privilege for the delivery, the use of &%-C%& causes
38112 privilege to be lost. However, root can test reception and delivery using two
38116 The WHITELIST_D_MACROS build option declares some macros to be safe to override
38117 with &%-D%& if the real uid is one of root, the Exim run-time user or the
38118 CONFIGURE_OWNER, if defined. The potential impact of this option is limited by
38119 requiring the run-time value supplied to &%-D%& to match a regex that errs on
38120 the restrictive side. Requiring build-time selection of safe macros is onerous
38121 but this option is intended solely as a transition mechanism to permit
38122 previously-working configurations to continue to work after release 4.73.
38124 If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option
38127 FIXED_NEVER_USERS can be set to a colon-separated list of users that are
38128 never to be used for any deliveries. This is like the &%never_users%& runtime
38129 option, but it cannot be overridden; the runtime option adds additional users
38130 to the list. The default setting is &"root"&; this prevents a non-root user who
38131 is permitted to modify the runtime file from using Exim as a way to get root.
38136 .section "Root privilege" "SECID270"
38138 .cindex "root privilege"
38139 The Exim binary is normally setuid to root, which means that it gains root
38140 privilege (runs as root) when it starts execution. In some special cases (for
38141 example, when the daemon is not in use and there are no local deliveries), it
38142 may be possible to run Exim setuid to some user other than root. This is
38143 discussed in the next section. However, in most installations, root privilege
38144 is required for two things:
38147 To set up a socket connected to the standard SMTP port (25) when initialising
38148 the listening daemon. If Exim is run from &'inetd'&, this privileged action is
38151 To be able to change uid and gid in order to read users' &_.forward_& files and
38152 perform local deliveries as the receiving user or as specified in the
38156 It is not necessary to be root to do any of the other things Exim does, such as
38157 receiving messages and delivering them externally over SMTP, and it is
38158 obviously more secure if Exim does not run as root except when necessary.
38159 For this reason, a user and group for Exim to use must be defined in
38160 &_Local/Makefile_&. These are known as &"the Exim user"& and &"the Exim
38161 group"&. Their values can be changed by the run time configuration, though this
38162 is not recommended. Often a user called &'exim'& is used, but some sites use
38163 &'mail'& or another user name altogether.
38165 Exim uses &[setuid()]& whenever it gives up root privilege. This is a permanent
38166 abdication; the process cannot regain root afterwards. Prior to release 4.00,
38167 &[seteuid()]& was used in some circumstances, but this is no longer the case.
38169 After a new Exim process has interpreted its command line options, it changes
38170 uid and gid in the following cases:
38175 If the &%-C%& option is used to specify an alternate configuration file, or if
38176 the &%-D%& option is used to define macro values for the configuration, and the
38177 calling process is not running as root, the uid and gid are changed to those of
38178 the calling process.
38179 However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%&
38180 option may not be used at all.
38181 If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values
38182 can be supplied if the calling process is running as root, the Exim run-time
38183 user or CONFIGURE_OWNER, if defined.
38188 If the expansion test option (&%-be%&) or one of the filter testing options
38189 (&%-bf%& or &%-bF%&) are used, the uid and gid are changed to those of the
38192 If the process is not a daemon process or a queue runner process or a delivery
38193 process or a process for testing address routing (started with &%-bt%&), the
38194 uid and gid are changed to the Exim user and group. This means that Exim always
38195 runs under its own uid and gid when receiving messages. This also applies when
38196 testing address verification
38199 (the &%-bv%& option) and testing incoming message policy controls (the &%-bh%&
38202 For a daemon, queue runner, delivery, or address testing process, the uid
38203 remains as root at this stage, but the gid is changed to the Exim group.
38206 The processes that initially retain root privilege behave as follows:
38209 A daemon process changes the gid to the Exim group and the uid to the Exim
38210 user after setting up one or more listening sockets. The &[initgroups()]&
38211 function is called, so that if the Exim user is in any additional groups, they
38212 will be used during message reception.
38214 A queue runner process retains root privilege throughout its execution. Its
38215 job is to fork a controlled sequence of delivery processes.
38217 A delivery process retains root privilege throughout most of its execution,
38218 but any actual deliveries (that is, the transports themselves) are run in
38219 subprocesses which always change to a non-root uid and gid. For local
38220 deliveries this is typically the uid and gid of the owner of the mailbox; for
38221 remote deliveries, the Exim uid and gid are used. Once all the delivery
38222 subprocesses have been run, a delivery process changes to the Exim uid and gid
38223 while doing post-delivery tidying up such as updating the retry database and
38224 generating bounce and warning messages.
38226 While the recipient addresses in a message are being routed, the delivery
38227 process runs as root. However, if a user's filter file has to be processed,
38228 this is done in a subprocess that runs under the individual user's uid and
38229 gid. A system filter is run as root unless &%system_filter_user%& is set.
38231 A process that is testing addresses (the &%-bt%& option) runs as root so that
38232 the routing is done in the same environment as a message delivery.
38238 .section "Running Exim without privilege" "SECTrunexiwitpri"
38239 .cindex "privilege, running without"
38240 .cindex "unprivileged running"
38241 .cindex "root privilege" "running without"
38242 Some installations like to run Exim in an unprivileged state for more of its
38243 operation, for added security. Support for this mode of operation is provided
38244 by the global option &%deliver_drop_privilege%&. When this is set, the uid and
38245 gid are changed to the Exim user and group at the start of a delivery process
38246 (and also queue runner and address testing processes). This means that address
38247 routing is no longer run as root, and the deliveries themselves cannot change
38251 .cindex "daemon" "restarting"
38252 Leaving the binary setuid to root, but setting &%deliver_drop_privilege%& means
38253 that the daemon can still be started in the usual way, and it can respond
38254 correctly to SIGHUP because the re-invocation regains root privilege.
38256 An alternative approach is to make Exim setuid to the Exim user and also setgid
38257 to the Exim group. If you do this, the daemon must be started from a root
38258 process. (Calling Exim from a root process makes it behave in the way it does
38259 when it is setuid root.) However, the daemon cannot restart itself after a
38260 SIGHUP signal because it cannot regain privilege.
38262 It is still useful to set &%deliver_drop_privilege%& in this case, because it
38263 stops Exim from trying to re-invoke itself to do a delivery after a message has
38264 been received. Such a re-invocation is a waste of resources because it has no
38267 If restarting the daemon is not an issue (for example, if &%mua_wrapper%& is
38268 set, or &'inetd'& is being used instead of a daemon), having the binary setuid
38269 to the Exim user seems a clean approach, but there is one complication:
38271 In this style of operation, Exim is running with the real uid and gid set to
38272 those of the calling process, and the effective uid/gid set to Exim's values.
38273 Ideally, any association with the calling process' uid/gid should be dropped,
38274 that is, the real uid/gid should be reset to the effective values so as to
38275 discard any privileges that the caller may have. While some operating systems
38276 have a function that permits this action for a non-root effective uid, quite a
38277 number of them do not. Because of this lack of standardization, Exim does not
38278 address this problem at this time.
38280 For this reason, the recommended approach for &"mostly unprivileged"& running
38281 is to keep the Exim binary setuid to root, and to set
38282 &%deliver_drop_privilege%&. This also has the advantage of allowing a daemon to
38283 be used in the most straightforward way.
38285 If you configure Exim not to run delivery processes as root, there are a
38286 number of restrictions on what you can do:
38289 You can deliver only as the Exim user/group. You should explicitly use the
38290 &%user%& and &%group%& options to override routers or local transports that
38291 normally deliver as the recipient. This makes sure that configurations that
38292 work in this mode function the same way in normal mode. Any implicit or
38293 explicit specification of another user causes an error.
38295 Use of &_.forward_& files is severely restricted, such that it is usually
38296 not worthwhile to include them in the configuration.
38298 Users who wish to use &_.forward_& would have to make their home directory and
38299 the file itself accessible to the Exim user. Pipe and append-to-file entries,
38300 and their equivalents in Exim filters, cannot be used. While they could be
38301 enabled in the Exim user's name, that would be insecure and not very useful.
38303 Unless the local user mailboxes are all owned by the Exim user (possible in
38304 some POP3 or IMAP-only environments):
38307 They must be owned by the Exim group and be writeable by that group. This
38308 implies you must set &%mode%& in the appendfile configuration, as well as the
38309 mode of the mailbox files themselves.
38311 You must set &%no_check_owner%&, since most or all of the files will not be
38312 owned by the Exim user.
38314 You must set &%file_must_exist%&, because Exim cannot set the owner correctly
38315 on a newly created mailbox when unprivileged. This also implies that new
38316 mailboxes need to be created manually.
38321 These restrictions severely restrict what can be done in local deliveries.
38322 However, there are no restrictions on remote deliveries. If you are running a
38323 gateway host that does no local deliveries, setting &%deliver_drop_privilege%&
38324 gives more security at essentially no cost.
38326 If you are using the &%mua_wrapper%& facility (see chapter
38327 &<<CHAPnonqueueing>>&), &%deliver_drop_privilege%& is forced to be true.
38332 .section "Delivering to local files" "SECID271"
38333 Full details of the checks applied by &(appendfile)& before it writes to a file
38334 are given in chapter &<<CHAPappendfile>>&.
38338 .section "Running local commands" "SECTsecconslocalcmds"
38339 .cindex "security" "local commands"
38340 .cindex "security" "command injection attacks"
38341 There are a number of ways in which an administrator can configure Exim to run
38342 commands based upon received, untrustworthy, data. Further, in some
38343 configurations a user who can control a &_.forward_& file can also arrange to
38344 run commands. Configuration to check includes, but is not limited to:
38347 Use of &%use_shell%& in the pipe transport: various forms of shell command
38348 injection may be possible with this option present. It is dangerous and should
38349 be used only with considerable caution. Consider constraints which whitelist
38350 allowed characters in a variable which is to be used in a pipe transport that
38351 has &%use_shell%& enabled.
38353 A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&,
38354 &%forbid_filter_dlfunc%& and so forth which restrict facilities available to
38355 &_.forward_& files in a redirect router. If Exim is running on a central mail
38356 hub to which ordinary users do not have shell access, but home directories are
38357 NFS mounted (for instance) then administrators should review the list of these
38358 forbid options available, and should bear in mind that the options that may
38359 need forbidding can change as new features are added between releases.
38361 The &%${run...}%& expansion item does not use a shell by default, but
38362 administrators can configure use of &_/bin/sh_& as part of the command.
38363 Such invocations should be viewed with prejudicial suspicion.
38365 Administrators who use embedded Perl are advised to explore how Perl's
38366 taint checking might apply to their usage.
38368 Use of &%${expand...}%& is somewhat analogous to shell's eval builtin and
38369 administrators are well advised to view its use with suspicion, in case (for
38370 instance) it allows a local-part to contain embedded Exim directives.
38372 Use of &%${match_local_part...}%& and friends becomes more dangerous if
38373 Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in
38374 each can reference arbitrary lists and files, rather than just being a list
38376 The EXPAND_LISTMATCH_RHS option was added and set false by default because of
38377 real-world security vulnerabilities caused by its use with untrustworthy data
38378 injected in, for SQL injection attacks.
38379 Consider the use of the &%inlisti%& expansion condition instead.
38385 .section "Trust in configuration data" "SECTsecconfdata"
38386 .cindex "security" "data sources"
38387 .cindex "security" "regular expressions"
38388 .cindex "regular expressions" "security"
38389 .cindex "PCRE" "security"
38390 If configuration data for Exim can come from untrustworthy sources, there
38391 are some issues to be aware of:
38394 Use of &%${expand...}%& may provide a path for shell injection attacks.
38396 Letting untrusted data provide a regular expression is unwise.
38398 Using &%${match...}%& to apply a fixed regular expression against untrusted
38399 data may result in pathological behaviour within PCRE. Be aware of what
38400 "backtracking" means and consider options for being more strict with a regular
38401 expression. Avenues to explore include limiting what can match (avoiding &`.`&
38402 when &`[a-z0-9]`& or other character class will do), use of atomic grouping and
38403 possessive quantifiers or just not using regular expressions against untrusted
38406 It can be important to correctly use &%${quote:...}%&,
38407 &%${quote_local_part:...}%& and &%${quote_%&<&'lookup-type'&>&%:...}%& expansion
38408 items to ensure that data is correctly constructed.
38410 Some lookups might return multiple results, even though normal usage is only
38411 expected to yield one result.
38417 .section "IPv4 source routing" "SECID272"
38418 .cindex "source routing" "in IP packets"
38419 .cindex "IP source routing"
38420 Many operating systems suppress IP source-routed packets in the kernel, but
38421 some cannot be made to do this, so Exim does its own check. It logs incoming
38422 IPv4 source-routed TCP calls, and then drops them. Things are all different in
38423 IPv6. No special checking is currently done.
38427 .section "The VRFY, EXPN, and ETRN commands in SMTP" "SECID273"
38428 Support for these SMTP commands is disabled by default. If required, they can
38429 be enabled by defining suitable ACLs.
38434 .section "Privileged users" "SECID274"
38435 .cindex "trusted users"
38436 .cindex "admin user"
38437 .cindex "privileged user"
38438 .cindex "user" "trusted"
38439 .cindex "user" "admin"
38440 Exim recognizes two sets of users with special privileges. Trusted users are
38441 able to submit new messages to Exim locally, but supply their own sender
38442 addresses and information about a sending host. For other users submitting
38443 local messages, Exim sets up the sender address from the uid, and doesn't
38444 permit a remote host to be specified.
38447 However, an untrusted user is permitted to use the &%-f%& command line option
38448 in the special form &%-f <>%& to indicate that a delivery failure for the
38449 message should not cause an error report. This affects the message's envelope,
38450 but it does not affect the &'Sender:'& header. Untrusted users may also be
38451 permitted to use specific forms of address with the &%-f%& option by setting
38452 the &%untrusted_set_sender%& option.
38454 Trusted users are used to run processes that receive mail messages from some
38455 other mail domain and pass them on to Exim for delivery either locally, or over
38456 the Internet. Exim trusts a caller that is running as root, as the Exim user,
38457 as any user listed in the &%trusted_users%& configuration option, or under any
38458 group listed in the &%trusted_groups%& option.
38460 Admin users are permitted to do things to the messages on Exim's queue. They
38461 can freeze or thaw messages, cause them to be returned to their senders, remove
38462 them entirely, or modify them in various ways. In addition, admin users can run
38463 the Exim monitor and see all the information it is capable of providing, which
38464 includes the contents of files on the spool.
38468 By default, the use of the &%-M%& and &%-q%& options to cause Exim to attempt
38469 delivery of messages on its queue is restricted to admin users. This
38470 restriction can be relaxed by setting the &%no_prod_requires_admin%& option.
38471 Similarly, the use of &%-bp%& (and its variants) to list the contents of the
38472 queue is also restricted to admin users. This restriction can be relaxed by
38473 setting &%no_queue_list_requires_admin%&.
38475 Exim recognizes an admin user if the calling process is running as root or as
38476 the Exim user or if any of the groups associated with the calling process is
38477 the Exim group. It is not necessary actually to be running under the Exim
38478 group. However, if admin users who are not root or the Exim user are to access
38479 the contents of files on the spool via the Exim monitor (which runs
38480 unprivileged), Exim must be built to allow group read access to its spool
38483 By default, regular users are trusted to perform basic testing and
38484 introspection commands, as themselves. This setting can be tightened by
38485 setting the &%commandline_checks_require_admin%& option.
38486 This affects most of the checking options,
38487 such as &%-be%& and anything else &%-b*%&.
38490 .section "Spool files" "SECID275"
38491 .cindex "spool directory" "files"
38492 Exim's spool directory and everything it contains is owned by the Exim user and
38493 set to the Exim group. The mode for spool files is defined in the
38494 &_Local/Makefile_& configuration file, and defaults to 0640. This means that
38495 any user who is a member of the Exim group can access these files.
38499 .section "Use of argv[0]" "SECID276"
38500 Exim examines the last component of &%argv[0]%&, and if it matches one of a set
38501 of specific strings, Exim assumes certain options. For example, calling Exim
38502 with the last component of &%argv[0]%& set to &"rsmtp"& is exactly equivalent
38503 to calling it with the option &%-bS%&. There are no security implications in
38508 .section "Use of %f formatting" "SECID277"
38509 The only use made of &"%f"& by Exim is in formatting load average values. These
38510 are actually stored in integer variables as 1000 times the load average.
38511 Consequently, their range is limited and so therefore is the length of the
38516 .section "Embedded Exim path" "SECID278"
38517 Exim uses its own path name, which is embedded in the code, only when it needs
38518 to re-exec in order to regain root privilege. Therefore, it is not root when it
38519 does so. If some bug allowed the path to get overwritten, it would lead to an
38520 arbitrary program's being run as exim, not as root.
38524 .section "Dynamic module directory" "SECTdynmoddir"
38525 Any dynamically loadable modules must be installed into the directory
38526 defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit
38530 .section "Use of sprintf()" "SECID279"
38531 .cindex "&[sprintf()]&"
38532 A large number of occurrences of &"sprintf"& in the code are actually calls to
38533 &'string_sprintf()'&, a function that returns the result in malloc'd store.
38534 The intermediate formatting is done into a large fixed buffer by a function
38535 that runs through the format string itself, and checks the length of each
38536 conversion before performing it, thus preventing buffer overruns.
38538 The remaining uses of &[sprintf()]& happen in controlled circumstances where
38539 the output buffer is known to be sufficiently long to contain the converted
38544 .section "Use of debug_printf() and log_write()" "SECID280"
38545 Arbitrary strings are passed to both these functions, but they do their
38546 formatting by calling the function &'string_vformat()'&, which runs through
38547 the format string itself, and checks the length of each conversion.
38551 .section "Use of strcat() and strcpy()" "SECID281"
38552 These are used only in cases where the output buffer is known to be large
38553 enough to hold the result.
38554 .ecindex IIDsecurcon
38559 . ////////////////////////////////////////////////////////////////////////////
38560 . ////////////////////////////////////////////////////////////////////////////
38562 .chapter "Format of spool files" "CHAPspool"
38563 .scindex IIDforspo1 "format" "spool files"
38564 .scindex IIDforspo2 "spool directory" "format of files"
38565 .scindex IIDforspo3 "spool files" "format of"
38566 .cindex "spool files" "editing"
38567 A message on Exim's queue consists of two files, whose names are the message id
38568 followed by -D and -H, respectively. The data portion of the message is kept in
38569 the -D file on its own. The message's envelope, status, and headers are all
38570 kept in the -H file, whose format is described in this chapter. Each of these
38571 two files contains the final component of its own name as its first line. This
38572 is insurance against disk crashes where the directory is lost but the files
38573 themselves are recoverable.
38575 Some people are tempted into editing -D files in order to modify messages. You
38576 need to be extremely careful if you do this; it is not recommended and you are
38577 on your own if you do it. Here are some of the pitfalls:
38580 You must ensure that Exim does not try to deliver the message while you are
38581 fiddling with it. The safest way is to take out a write lock on the -D file,
38582 which is what Exim itself does, using &[fcntl()]&. If you update the file in
38583 place, the lock will be retained. If you write a new file and rename it, the
38584 lock will be lost at the instant of rename.
38586 .vindex "&$body_linecount$&"
38587 If you change the number of lines in the file, the value of
38588 &$body_linecount$&, which is stored in the -H file, will be incorrect and can
38589 cause incomplete transmission of messages or undeliverable messages.
38591 If the message is in MIME format, you must take care not to break it.
38593 If the message is cryptographically signed, any change will invalidate the
38596 All in all, modifying -D files is fraught with danger.
38598 Files whose names end with -J may also be seen in the &_input_& directory (or
38599 its subdirectories when &%split_spool_directory%& is set). These are journal
38600 files, used to record addresses to which the message has been delivered during
38601 the course of a delivery attempt. If there are still undelivered recipients at
38602 the end, the -H file is updated, and the -J file is deleted. If, however, there
38603 is some kind of crash (for example, a power outage) before this happens, the -J
38604 file remains in existence. When Exim next processes the message, it notices the
38605 -J file and uses it to update the -H file before starting the next delivery
38608 Files whose names end with -K or .eml may also be seen in the spool.
38609 These are temporaries used for DKIM or malware processing, when that is used.
38610 They should be tidied up by normal operations; any old ones are probably
38611 relics of crashes and can be removed.
38613 .section "Format of the -H file" "SECID282"
38614 .cindex "uid (user id)" "in spool file"
38615 .cindex "gid (group id)" "in spool file"
38616 The second line of the -H file contains the login name for the uid of the
38617 process that called Exim to read the message, followed by the numerical uid and
38618 gid. For a locally generated message, this is normally the user who sent the
38619 message. For a message received over TCP/IP via the daemon, it is
38620 normally the Exim user.
38622 The third line of the file contains the address of the message's sender as
38623 transmitted in the envelope, contained in angle brackets. The sender address is
38624 empty for bounce messages. For incoming SMTP mail, the sender address is given
38625 in the MAIL command. For locally generated mail, the sender address is
38626 created by Exim from the login name of the current user and the configured
38627 &%qualify_domain%&. However, this can be overridden by the &%-f%& option or a
38628 leading &"From&~"& line if the caller is trusted, or if the supplied address is
38629 &"<>"& or an address that matches &%untrusted_set_senders%&.
38631 The fourth line contains two numbers. The first is the time that the message
38632 was received, in the conventional Unix form &-- the number of seconds since the
38633 start of the epoch. The second number is a count of the number of messages
38634 warning of delayed delivery that have been sent to the sender.
38636 There follow a number of lines starting with a hyphen. These can appear in any
38637 order, and are omitted when not relevant:
38640 .vitem "&%-acl%&&~<&'number'&>&~<&'length'&>"
38641 This item is obsolete, and is not generated from Exim release 4.61 onwards;
38642 &%-aclc%& and &%-aclm%& are used instead. However, &%-acl%& is still
38643 recognized, to provide backward compatibility. In the old format, a line of
38644 this form is present for every ACL variable that is not empty. The number
38645 identifies the variable; the &%acl_c%&&*x*& variables are numbered 0&--9 and
38646 the &%acl_m%&&*x*& variables are numbered 10&--19. The length is the length of
38647 the data string for the variable. The string itself starts at the beginning of
38648 the next line, and is followed by a newline character. It may contain internal
38651 .vitem "&%-aclc%&&~<&'rest-of-name'&>&~<&'length'&>"
38652 A line of this form is present for every ACL connection variable that is
38653 defined. Note that there is a space between &%-aclc%& and the rest of the name.
38654 The length is the length of the data string for the variable. The string itself
38655 starts at the beginning of the next line, and is followed by a newline
38656 character. It may contain internal newlines.
38658 .vitem "&%-aclm%&&~<&'rest-of-name'&>&~<&'length'&>"
38659 A line of this form is present for every ACL message variable that is defined.
38660 Note that there is a space between &%-aclm%& and the rest of the name. The
38661 length is the length of the data string for the variable. The string itself
38662 starts at the beginning of the next line, and is followed by a newline
38663 character. It may contain internal newlines.
38665 .vitem "&%-active_hostname%&&~<&'hostname'&>"
38666 This is present if, when the message was received over SMTP, the value of
38667 &$smtp_active_hostname$& was different to the value of &$primary_hostname$&.
38669 .vitem &%-allow_unqualified_recipient%&
38670 This is present if unqualified recipient addresses are permitted in header
38671 lines (to stop such addresses from being qualified if rewriting occurs at
38672 transport time). Local messages that were input using &%-bnq%& and remote
38673 messages from hosts that match &%recipient_unqualified_hosts%& set this flag.
38675 .vitem &%-allow_unqualified_sender%&
38676 This is present if unqualified sender addresses are permitted in header lines
38677 (to stop such addresses from being qualified if rewriting occurs at transport
38678 time). Local messages that were input using &%-bnq%& and remote messages from
38679 hosts that match &%sender_unqualified_hosts%& set this flag.
38681 .vitem "&%-auth_id%&&~<&'text'&>"
38682 The id information for a message received on an authenticated SMTP connection
38683 &-- the value of the &$authenticated_id$& variable.
38685 .vitem "&%-auth_sender%&&~<&'address'&>"
38686 The address of an authenticated sender &-- the value of the
38687 &$authenticated_sender$& variable.
38689 .vitem "&%-body_linecount%&&~<&'number'&>"
38690 This records the number of lines in the body of the message, and is
38691 present unless &%-spool_file_wireformat%& is.
38693 .vitem "&%-body_zerocount%&&~<&'number'&>"
38694 This records the number of binary zero bytes in the body of the message, and is
38695 present if the number is greater than zero.
38697 .vitem &%-deliver_firsttime%&
38698 This is written when a new message is first added to the spool. When the spool
38699 file is updated after a deferral, it is omitted.
38701 .vitem "&%-frozen%&&~<&'time'&>"
38702 .cindex "frozen messages" "spool data"
38703 The message is frozen, and the freezing happened at <&'time'&>.
38705 .vitem "&%-helo_name%&&~<&'text'&>"
38706 This records the host name as specified by a remote host in a HELO or EHLO
38709 .vitem "&%-host_address%&&~<&'address'&>.<&'port'&>"
38710 This records the IP address of the host from which the message was received and
38711 the remote port number that was used. It is omitted for locally generated
38714 .vitem "&%-host_auth%&&~<&'text'&>"
38715 If the message was received on an authenticated SMTP connection, this records
38716 the name of the authenticator &-- the value of the
38717 &$sender_host_authenticated$& variable.
38719 .vitem &%-host_lookup_failed%&
38720 This is present if an attempt to look up the sending host's name from its IP
38721 address failed. It corresponds to the &$host_lookup_failed$& variable.
38723 .vitem "&%-host_name%&&~<&'text'&>"
38724 .cindex "reverse DNS lookup"
38725 .cindex "DNS" "reverse lookup"
38726 This records the name of the remote host from which the message was received,
38727 if the host name was looked up from the IP address when the message was being
38728 received. It is not present if no reverse lookup was done.
38730 .vitem "&%-ident%&&~<&'text'&>"
38731 For locally submitted messages, this records the login of the originating user,
38732 unless it was a trusted user and the &%-oMt%& option was used to specify an
38733 ident value. For messages received over TCP/IP, this records the ident string
38734 supplied by the remote host, if any.
38736 .vitem "&%-interface_address%&&~<&'address'&>.<&'port'&>"
38737 This records the IP address of the local interface and the port number through
38738 which a message was received from a remote host. It is omitted for locally
38739 generated messages.
38742 The message is from a local sender.
38744 .vitem &%-localerror%&
38745 The message is a locally-generated bounce message.
38747 .vitem "&%-local_scan%&&~<&'string'&>"
38748 This records the data string that was returned by the &[local_scan()]& function
38749 when the message was received &-- the value of the &$local_scan_data$&
38750 variable. It is omitted if no data was returned.
38752 .vitem &%-manual_thaw%&
38753 The message was frozen but has been thawed manually, that is, by an explicit
38754 Exim command rather than via the auto-thaw process.
38757 A testing delivery process was started using the &%-N%& option to suppress any
38758 actual deliveries, but delivery was deferred. At any further delivery attempts,
38761 .vitem &%-received_protocol%&
38762 This records the value of the &$received_protocol$& variable, which contains
38763 the name of the protocol by which the message was received.
38765 .vitem &%-sender_set_untrusted%&
38766 The envelope sender of this message was set by an untrusted local caller (used
38767 to ensure that the caller is displayed in queue listings).
38769 .vitem "&%-spam_score_int%&&~<&'number'&>"
38770 If a message was scanned by SpamAssassin, this is present. It records the value
38771 of &$spam_score_int$&.
38773 .vitem &%-spool_file_wireformat%&
38774 The -D file for this message is in wire-format (for ESMTP CHUNKING)
38775 rather than Unix-format.
38776 The line-ending is CRLF rather than newline.
38777 There is still, however, no leading-dot-stuffing.
38779 .vitem &%-tls_certificate_verified%&
38780 A TLS certificate was received from the client that sent this message, and the
38781 certificate was verified by the server.
38783 .vitem "&%-tls_cipher%&&~<&'cipher name'&>"
38784 When the message was received over an encrypted connection, this records the
38785 name of the cipher suite that was used.
38787 .vitem "&%-tls_peerdn%&&~<&'peer DN'&>"
38788 When the message was received over an encrypted connection, and a certificate
38789 was received from the client, this records the Distinguished Name from that
38793 Following the options there is a list of those addresses to which the message
38794 is not to be delivered. This set of addresses is initialized from the command
38795 line when the &%-t%& option is used and &%extract_addresses_remove_arguments%&
38796 is set; otherwise it starts out empty. Whenever a successful delivery is made,
38797 the address is added to this set. The addresses are kept internally as a
38798 balanced binary tree, and it is a representation of that tree which is written
38799 to the spool file. If an address is expanded via an alias or forward file, the
38800 original address is added to the tree when deliveries to all its child
38801 addresses are complete.
38803 If the tree is empty, there is a single line in the spool file containing just
38804 the text &"XX"&. Otherwise, each line consists of two letters, which are either
38805 Y or N, followed by an address. The address is the value for the node of the
38806 tree, and the letters indicate whether the node has a left branch and/or a
38807 right branch attached to it, respectively. If branches exist, they immediately
38808 follow. Here is an example of a three-node tree:
38810 YY darcy@austen.fict.example
38811 NN alice@wonderland.fict.example
38812 NN editor@thesaurus.ref.example
38814 After the non-recipients tree, there is a list of the message's recipients.
38815 This is a simple list, preceded by a count. It includes all the original
38816 recipients of the message, including those to whom the message has already been
38817 delivered. In the simplest case, the list contains one address per line. For
38821 editor@thesaurus.ref.example
38822 darcy@austen.fict.example
38824 alice@wonderland.fict.example
38826 However, when a child address has been added to the top-level addresses as a
38827 result of the use of the &%one_time%& option on a &(redirect)& router, each
38828 line is of the following form:
38830 <&'top-level address'&> <&'errors_to address'&> &&&
38831 <&'length'&>,<&'parent number'&>#<&'flag bits'&>
38833 The 01 flag bit indicates the presence of the three other fields that follow
38834 the top-level address. Other bits may be used in future to support additional
38835 fields. The <&'parent number'&> is the offset in the recipients list of the
38836 original parent of the &"one time"& address. The first two fields are the
38837 envelope sender that is associated with this address and its length. If the
38838 length is zero, there is no special envelope sender (there are then two space
38839 characters in the line). A non-empty field can arise from a &(redirect)& router
38840 that has an &%errors_to%& setting.
38843 A blank line separates the envelope and status information from the headers
38844 which follow. A header may occupy several lines of the file, and to save effort
38845 when reading it in, each header is preceded by a number and an identifying
38846 character. The number is the number of characters in the header, including any
38847 embedded newlines and the terminating newline. The character is one of the
38851 .row <&'blank'&> "header in which Exim has no special interest"
38852 .row &`B`& "&'Bcc:'& header"
38853 .row &`C`& "&'Cc:'& header"
38854 .row &`F`& "&'From:'& header"
38855 .row &`I`& "&'Message-id:'& header"
38856 .row &`P`& "&'Received:'& header &-- P for &""postmark""&"
38857 .row &`R`& "&'Reply-To:'& header"
38858 .row &`S`& "&'Sender:'& header"
38859 .row &`T`& "&'To:'& header"
38860 .row &`*`& "replaced or deleted header"
38863 Deleted or replaced (rewritten) headers remain in the spool file for debugging
38864 purposes. They are not transmitted when the message is delivered. Here is a
38865 typical set of headers:
38867 111P Received: by hobbit.fict.example with local (Exim 4.00)
38868 id 14y9EI-00026G-00; Fri, 11 May 2001 10:28:59 +0100
38869 049 Message-Id: <E14y9EI-00026G-00@hobbit.fict.example>
38870 038* X-rewrote-sender: bb@hobbit.fict.example
38871 042* From: Bilbo Baggins <bb@hobbit.fict.example>
38872 049F From: Bilbo Baggins <B.Baggins@hobbit.fict.example>
38873 099* To: alice@wonderland.fict.example, rdo@foundation,
38874 darcy@austen.fict.example, editor@thesaurus.ref.example
38875 104T To: alice@wonderland.fict.example, rdo@foundation.example,
38876 darcy@austen.fict.example, editor@thesaurus.ref.example
38877 038 Date: Fri, 11 May 2001 10:28:59 +0100
38879 The asterisked headers indicate that the envelope sender, &'From:'& header, and
38880 &'To:'& header have been rewritten, the last one because routing expanded the
38881 unqualified domain &'foundation'&.
38882 .ecindex IIDforspo1
38883 .ecindex IIDforspo2
38884 .ecindex IIDforspo3
38886 .section "Format of the -D file" "SECID282a"
38887 The data file is traditionally in Unix-standard format: lines are ended with
38888 an ASCII newline character.
38889 However, when the &%spool_wireformat%& main option is used some -D files
38890 can have an alternate format.
38891 This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
38892 The -D file lines (not including the first name-component line) are
38893 suitable for direct copying to the wire when transmitting using the
38894 ESMTP CHUNKING option, meaning lower processing overhead.
38895 Lines are terminated with an ASCII CRLF pair.
38896 There is no dot-stuffing (and no dot-termination).
38898 . ////////////////////////////////////////////////////////////////////////////
38899 . ////////////////////////////////////////////////////////////////////////////
38901 .chapter "DKIM and SPF" "CHAPdkim" &&&
38902 "DKIM and SPF Support"
38905 .section "DKIM (DomainKeys Identified Mail)" SECDKIM
38907 DKIM is a mechanism by which messages sent by some entity can be provably
38908 linked to a domain which that entity controls. It permits reputation to
38909 be tracked on a per-domain basis, rather than merely upon source IP address.
38910 DKIM is documented in RFC 6376.
38912 As DKIM relies on the message being unchanged in transit, messages handled
38913 by a mailing-list (which traditionally adds to the message) will not match
38914 any original DKIM signature.
38916 DKIM support is compiled into Exim by default if TLS support is present.
38917 It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&.
38919 Exim's DKIM implementation allows for
38921 Signing outgoing messages: This function is implemented in the SMTP transport.
38922 It can co-exist with all other Exim features
38923 (including transport filters)
38924 except cutthrough delivery.
38926 Verifying signatures in incoming messages: This is implemented by an additional
38927 ACL (acl_smtp_dkim), which can be called several times per message, with
38928 different signature contexts.
38931 In typical Exim style, the verification implementation does not include any
38932 default "policy". Instead it enables you to build your own policy using
38933 Exim's standard controls.
38935 Please note that verification of DKIM signatures in incoming mail is turned
38936 on by default for logging (in the <= line) purposes.
38938 Additional log detail can be enabled using the &%dkim_verbose%& log_selector.
38939 When set, for each signature in incoming email,
38940 exim will log a line displaying the most important signature details, and the
38941 signature status. Here is an example (with line-breaks added for clarity):
38943 2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM:
38944 d=facebookmail.com s=q1-2009b
38945 c=relaxed/relaxed a=rsa-sha1
38946 i=@facebookmail.com t=1252484542 [verification succeeded]
38949 You might want to turn off DKIM verification processing entirely for internal
38950 or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL
38951 control modifier. This should typically be done in the RCPT ACL, at points
38952 where you accept mail from relay sources (internal hosts or authenticated
38956 .section "Signing outgoing messages" "SECDKIMSIGN"
38957 .cindex "DKIM" "signing"
38959 For signing to be usable you must have published a DKIM record in DNS.
38960 Note that RFC 8301 says:
38962 rsa-sha1 MUST NOT be used for signing or verifying.
38964 Signers MUST use RSA keys of at least 1024 bits for all keys.
38965 Signers SHOULD use RSA keys of at least 2048 bits.
38968 Note also that the key content (the 'p=' field)
38969 in the DNS record is different between RSA and EC keys;
38970 for the former it is the base64 of the ASN.1 for the RSA public key
38971 (equivalent to the private-key .pem with the header/trailer stripped)
38972 but for EC keys it is the base64 of the pure key; no ASN.1 wrapping.
38974 Signing is enabled by setting private options on the SMTP transport.
38975 These options take (expandable) strings as arguments.
38977 .option dkim_domain smtp string list&!! unset
38978 The domain(s) you want to sign with.
38979 After expansion, this can be a list.
38980 Each element in turn is put into the &%$dkim_domain%& expansion variable
38981 while expanding the remaining signing options.
38982 If it is empty after expansion, DKIM signing is not done,
38983 and no error will result even if &%dkim_strict%& is set.
38985 .option dkim_selector smtp string list&!! unset
38986 This sets the key selector string.
38987 After expansion, which can use &$dkim_domain$&, this can be a list.
38988 Each element in turn is put in the expansion
38989 variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
38990 option along with &%$dkim_domain%&.
38991 If the option is empty after expansion, DKIM signing is not done for this domain,
38992 and no error will result even if &%dkim_strict%& is set.
38994 .option dkim_private_key smtp string&!! unset
38995 This sets the private key to use.
38996 You can use the &%$dkim_domain%& and
38997 &%$dkim_selector%& expansion variables to determine the private key to use.
38998 The result can either
39000 be a valid RSA private key in ASCII armor (.pem file), including line breaks
39002 with GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
39003 be a valid Ed25519 private key (same format as above)
39005 start with a slash, in which case it is treated as a file that contains
39008 be "0", "false" or the empty string, in which case the message will not
39009 be signed. This case will not result in an error, even if &%dkim_strict%&
39013 To generate keys under OpenSSL:
39015 openssl genrsa -out dkim_rsa.private 2048
39016 openssl rsa -in dkim_rsa.private -out /dev/stdout -pubout -outform PEM
39018 Take the base-64 lines from the output of the second command, concatenated,
39019 for the DNS TXT record.
39020 See section 3.6 of RFC6376 for the record specification.
39024 certtool --generate-privkey --rsa --bits=2048 --password='' -8 --outfile=dkim_rsa.private
39025 certtool --load-privkey=dkim_rsa.private --pubkey-info
39028 Note that RFC 8301 says:
39030 Signers MUST use RSA keys of at least 1024 bits for all keys.
39031 Signers SHOULD use RSA keys of at least 2048 bits.
39034 Support for EC keys is being developed under
39035 &url(https://datatracker.ietf.org/doc/draft-ietf-dcrup-dkim-crypto/).
39036 They are considerably smaller than RSA keys for equivalent protection.
39037 As they are a recent development, users should consider dual-signing
39038 (by setting a list of selectors, and an expansion for this option)
39039 for some transition period.
39040 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
39043 OpenSSL 1.1.1 and GnuTLS 3.6.0 can create Ed25519 private keys:
39045 openssl genpkey -algorithm ed25519 -out dkim_ed25519.private
39046 certtool --generate-privkey --key-type=ed25519 --outfile=dkim_ed25519.private
39049 To produce the required public key value for a DNS record:
39051 openssl pkey -outform DER -pubout -in dkim_ed25519.private | tail -c +13 | base64
39052 certtool --load_privkey=dkim_ed25519.private --pubkey_info --outder | tail -c +13 | base64
39055 Note that the format
39056 of Ed25519 keys in DNS has not yet been decided; this release supports
39057 both of the leading candidates at this time, a future release will
39058 probably drop support for whichever proposal loses.
39060 .option dkim_hash smtp string&!! sha256
39061 Can be set to any one of the supported hash methods, which are:
39063 &`sha1`& &-- should not be used, is old and insecure
39065 &`sha256`& &-- the default
39067 &`sha512`& &-- possibly more secure but less well supported
39070 Note that RFC 8301 says:
39072 rsa-sha1 MUST NOT be used for signing or verifying.
39075 .option dkim_identity smtp string&!! unset
39076 If set after expansion, the value is used to set an "i=" tag in
39077 the signing header. The DKIM standards restrict the permissible
39078 syntax of this optional tag to a mail address, with possibly-empty
39079 local part, an @, and a domain identical to or subdomain of the "d="
39080 tag value. Note that Exim does not check the value.
39082 .option dkim_canon smtp string&!! unset
39083 This option sets the canonicalization method used when signing a message.
39084 The DKIM RFC currently supports two methods: "simple" and "relaxed".
39085 The option defaults to "relaxed" when unset. Note: the current implementation
39086 only supports signing with the same canonicalization method for both headers and body.
39088 .option dkim_strict smtp string&!! unset
39089 This option defines how Exim behaves when signing a message that
39090 should be signed fails for some reason. When the expansion evaluates to
39091 either "1" or "true", Exim will defer. Otherwise Exim will send the message
39092 unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
39095 .option dkim_sign_headers smtp string&!! "see below"
39096 If set, this option must expand to a colon-separated
39097 list of header names.
39098 Headers with these names, or the absence or such a header, will be included
39099 in the message signature.
39100 When unspecified, the header names listed in RFC4871 will be used,
39101 whether or not each header is present in the message.
39102 The default list is available for the expansion in the macro
39103 "_DKIM_SIGN_HEADERS".
39105 If a name is repeated, multiple headers by that name (or the absence thereof)
39106 will be signed. The textually later headers in the headers part of the
39107 message are signed first, if there are multiples.
39109 A name can be prefixed with either an '=' or a '+' character.
39110 If an '=' prefix is used, all headers that are present with this name
39112 If a '+' prefix if used, all headers that are present with this name
39113 will be signed, and one signature added for a missing header with the
39114 name will be appended.
39117 .option dkim_timestamps smtp integer&!! unset
39118 This option controls the inclusion of timestamp information in the signature.
39119 If not set, no such information will be included.
39120 Otherwise, must be an unsigned number giving an offset in seconds from the current time
39122 (eg. 1209600 for two weeks);
39123 both creation (t=) and expiry (x=) tags will be included.
39125 RFC 6376 lists these tags as RECOMMENDED.
39129 .section "Verifying DKIM signatures in incoming mail" "SECDKIMVFY"
39130 .cindex "DKIM" "verification"
39133 Verification of DKIM signatures in SMTP incoming email is done for all
39134 messages for which an ACL control &%dkim_disable_verify%& has not been set.
39135 .cindex authentication "expansion item"
39136 Performing verification sets up information used by the
39137 &$authresults$& expansion item.
39140 .new The results of that verification are then made available to the
39141 &%acl_smtp_dkim%& ACL, &new(which can examine and modify them).
39142 By default, this ACL is called once for each
39143 syntactically(!) correct signature in the incoming message.
39144 A missing ACL definition defaults to accept.
39145 If any ACL call does not accept, the message is not accepted.
39146 If a cutthrough delivery was in progress for the message, that is
39147 summarily dropped (having wasted the transmission effort).
39149 To evaluate the &new(verification result) in the ACL
39150 a large number of expansion variables
39151 containing the signature status and its details are set up during the
39152 runtime of the ACL.
39154 Calling the ACL only for existing signatures is not sufficient to build
39155 more advanced policies. For that reason, the global option
39156 &%dkim_verify_signers%&, and a global expansion variable
39157 &%$dkim_signers%& exist.
39159 The global option &%dkim_verify_signers%& can be set to a colon-separated
39160 list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is
39161 called. It is expanded when the message has been received. At this point,
39162 the expansion variable &%$dkim_signers%& already contains a colon-separated
39163 list of signer domains and identities for the message. When
39164 &%dkim_verify_signers%& is not specified in the main configuration,
39167 dkim_verify_signers = $dkim_signers
39169 This leads to the default behaviour of calling &%acl_smtp_dkim%& for each
39170 DKIM signature in the message. Current DKIM verifiers may want to explicitly
39171 call the ACL for known domains or identities. This would be achieved as follows:
39173 dkim_verify_signers = paypal.com:ebay.com:$dkim_signers
39175 This would result in &%acl_smtp_dkim%& always being called for "paypal.com"
39176 and "ebay.com", plus all domains and identities that have signatures in the message.
39177 You can also be more creative in constructing your policy. For example:
39179 dkim_verify_signers = $sender_address_domain:$dkim_signers
39182 If a domain or identity is listed several times in the (expanded) value of
39183 &%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
39185 If multiple signatures match a domain (or identity), the ACL is called once
39186 for each matching signature.
39189 Inside the &%acl_smtp_dkim%&, the following expansion variables are
39190 available (from most to least important):
39194 .vitem &%$dkim_cur_signer%&
39195 The signer that is being evaluated in this ACL run. This can be a domain or
39196 an identity. This is one of the list items from the expanded main option
39197 &%dkim_verify_signers%& (see above).
39199 .vitem &%$dkim_verify_status%&
39200 Within the DKIM ACL,
39201 a string describing the general status of the signature. One of
39203 &%none%&: There is no signature in the message for the current domain or
39204 identity (as reflected by &%$dkim_cur_signer%&).
39206 &%invalid%&: The signature could not be verified due to a processing error.
39207 More detail is available in &%$dkim_verify_reason%&.
39209 &%fail%&: Verification of the signature failed. More detail is
39210 available in &%$dkim_verify_reason%&.
39212 &%pass%&: The signature passed verification. It is valid.
39215 This variable can be overwritten using an ACL 'set' modifier.
39216 This might, for instance, be done to enforce a policy restriction on
39217 hash-method or key-size:
39219 warn condition = ${if eq {$dkim_verify_status}{pass}}
39220 condition = ${if eq {${length_3:$dkim_algo}}{rsa}}
39221 condition = ${if or {{eq {$dkim_algo}{rsa-sha1}} \
39222 {< {$dkim_key_length}{1024}}}}
39223 logwrite = NOTE: forcing DKIM verify fail (was pass)
39224 set dkim_verify_status = fail
39225 set dkim_verify_reason = hash too weak or key too short
39228 After all the DKIM ACL runs have completed, the value becomes a
39229 colon-separated list of the values after each run.
39231 .vitem &%$dkim_verify_reason%&
39232 A string giving a little bit more detail when &%$dkim_verify_status%& is either
39233 "fail" or "invalid". One of
39235 &%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public
39236 key for the domain could not be retrieved. This may be a temporary problem.
39238 &%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key
39239 record for the domain is syntactically invalid.
39241 &%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated
39242 body hash does not match the one specified in the signature header. This
39243 means that the message body was modified in transit.
39245 &%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature
39246 could not be verified. This may mean that headers were modified,
39247 re-written or otherwise changed in a way which is incompatible with
39248 DKIM verification. It may of course also mean that the signature is forged.
39251 This variable can be overwritten, with any value, using an ACL 'set' modifier.
39253 .vitem &%$dkim_domain%&
39254 The signing domain. IMPORTANT: This variable is only populated if there is
39255 an actual signature in the message for the current domain or identity (as
39256 reflected by &%$dkim_cur_signer%&).
39258 .vitem &%$dkim_identity%&
39259 The signing identity, if present. IMPORTANT: This variable is only populated
39260 if there is an actual signature in the message for the current domain or
39261 identity (as reflected by &%$dkim_cur_signer%&).
39263 .vitem &%$dkim_selector%&
39264 The key record selector string.
39266 .vitem &%$dkim_algo%&
39267 The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'.
39268 If running under GnuTLS 3.6.0 or OpenSSL 1.1.1 or later,
39269 may also be 'ed25519-sha256'.
39270 The "_CRYPTO_SIGN_ED25519" macro will be defined if support is present
39273 Note that RFC 8301 says:
39275 rsa-sha1 MUST NOT be used for signing or verifying.
39277 DKIM signatures identified as having been signed with historic
39278 algorithms (currently, rsa-sha1) have permanently failed evaluation
39281 To enforce this you must have a DKIM ACL which checks this variable
39282 and overwrites the &$dkim_verify_status$& variable as discussed above.
39284 .vitem &%$dkim_canon_body%&
39285 The body canonicalization method. One of 'relaxed' or 'simple'.
39287 .vitem &%$dkim_canon_headers%&
39288 The header canonicalization method. One of 'relaxed' or 'simple'.
39290 .vitem &%$dkim_copiedheaders%&
39291 A transcript of headers and their values which are included in the signature
39292 (copied from the 'z=' tag of the signature).
39293 Note that RFC6376 requires that verification fail if the From: header is
39294 not included in the signature. Exim does not enforce this; sites wishing
39295 strict enforcement should code the check explicitly.
39297 .vitem &%$dkim_bodylength%&
39298 The number of signed body bytes. If zero ("0"), the body is unsigned. If no
39299 limit was set by the signer, "9999999999999" is returned. This makes sure
39300 that this variable always expands to an integer value.
39302 &*Note:*& The presence of the signature tag specifying a signing body length
39303 is one possible route to spoofing of valid DKIM signatures.
39304 A paranoid implementation might wish to regard signature where this variable
39305 shows less than the "no limit" return as being invalid.
39308 .vitem &%$dkim_created%&
39309 UNIX timestamp reflecting the date and time when the signature was created.
39310 When this was not specified by the signer, "0" is returned.
39312 .vitem &%$dkim_expires%&
39313 UNIX timestamp reflecting the date and time when the signer wants the
39314 signature to be treated as "expired". When this was not specified by the
39315 signer, "9999999999999" is returned. This makes it possible to do useful
39316 integer size comparisons against this value.
39317 Note that Exim does not check this value.
39319 .vitem &%$dkim_headernames%&
39320 A colon-separated list of names of headers included in the signature.
39322 .vitem &%$dkim_key_testing%&
39323 "1" if the key record has the "testing" flag set, "0" if not.
39325 .vitem &%$dkim_key_nosubdomains%&
39326 "1" if the key record forbids subdomaining, "0" otherwise.
39328 .vitem &%$dkim_key_srvtype%&
39329 Service type (tag s=) from the key record. Defaults to "*" if not specified
39332 .vitem &%$dkim_key_granularity%&
39333 Key granularity (tag g=) from the key record. Defaults to "*" if not specified
39336 .vitem &%$dkim_key_notes%&
39337 Notes from the key record (tag n=).
39339 .vitem &%$dkim_key_length%&
39340 Number of bits in the key.
39342 Note that RFC 8301 says:
39344 Verifiers MUST NOT consider signatures using RSA keys of
39345 less than 1024 bits as valid signatures.
39348 To enforce this you must have a DKIM ACL which checks this variable
39349 and overwrites the &$dkim_verify_status$& variable as discussed above.
39350 As EC keys are much smaller, the check should only do this for RSA keys.
39354 In addition, two ACL conditions are provided:
39357 .vitem &%dkim_signers%&
39358 ACL condition that checks a colon-separated list of domains or identities
39359 for a match against the domain or identity that the ACL is currently verifying
39360 (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL
39361 verb to a group of domains or identities. For example:
39364 # Warn when Mail purportedly from GMail has no gmail signature
39365 warn log_message = GMail sender without gmail.com DKIM signature
39366 sender_domains = gmail.com
39367 dkim_signers = gmail.com
39371 Note that the above does not check for a total lack of DKIM signing;
39372 for that check for empty &$h_DKIM-Signature:$& in the data ACL.
39374 .vitem &%dkim_status%&
39375 ACL condition that checks a colon-separated list of possible DKIM verification
39376 results against the actual result of verification. This is typically used
39377 to restrict an ACL verb to a list of verification outcomes, for example:
39380 deny message = Mail from Paypal with invalid/missing signature
39381 sender_domains = paypal.com:paypal.de
39382 dkim_signers = paypal.com:paypal.de
39383 dkim_status = none:invalid:fail
39386 The possible status keywords are: 'none','invalid','fail' and 'pass'. Please
39387 see the documentation of the &%$dkim_verify_status%& expansion variable above
39388 for more information of what they mean.
39394 .section "SPF (Sender Policy Framework)" SECSPF
39395 .cindex SPF verification
39397 SPF is a mechanism whereby a domain may assert which IP addresses may transmit
39398 messages with its domain in the envelope from, documented by RFC 7208.
39399 For more information on SPF see &url(http://www.openspf.org).
39401 Messages sent by a system not authorised will fail checking of such assertions.
39402 This includes retransmissions done by traditional forwarders.
39404 SPF verification support is built into Exim if SUPPORT_SPF=yes is set in
39405 &_Local/Makefile_&. The support uses the &_libspf2_& library
39406 &url(http://www.libspf2.org/).
39407 There is no Exim involvement in the transmission of messages;
39408 publishing certain DNS records is all that is required.
39410 For verification, an ACL condition and an expansion lookup are provided.
39411 .cindex authentication "expansion item"
39412 Performing verification sets up information used by the
39413 &$authresults$& expansion item.
39416 .cindex SPF "ACL condition"
39417 .cindex ACL "spf condition"
39418 The ACL condition "spf" can be used at or after the MAIL ACL.
39419 It takes as an argument a list of strings giving the outcome of the SPF check,
39420 and will succeed for any matching outcome.
39424 The SPF check passed, the sending host is positively verified by SPF.
39427 The SPF check failed, the sending host is NOT allowed to send mail for the
39428 domain in the envelope-from address.
39430 .vitem &%softfail%&
39431 The SPF check failed, but the queried domain can't absolutely confirm that this
39435 The queried domain does not publish SPF records.
39438 The SPF check returned a "neutral" state. This means the queried domain has
39439 published a SPF record, but wants to allow outside servers to send mail under
39440 its domain as well. This should be treated like "none".
39442 .vitem &%permerror%&
39443 This indicates a syntax error in the SPF record of the queried domain.
39444 You may deny messages when this occurs.
39446 .vitem &%temperror%&
39447 This indicates a temporary error during all processing, including Exim's
39448 SPF processing. You may defer messages when this occurs.
39451 You can prefix each string with an exclamation mark to invert
39452 its meaning, for example "!fail" will match all results but
39453 "fail". The string list is evaluated left-to-right, in a
39454 short-circuit fashion.
39459 message = $sender_host_address is not allowed to send mail from \
39460 ${if def:sender_address_domain \
39461 {$sender_address_domain}{$sender_helo_name}}. \
39462 Please see http://www.openspf.org/Why?scope=\
39463 ${if def:sender_address_domain {mfrom}{helo}};\
39464 identity=${if def:sender_address_domain \
39465 {$sender_address}{$sender_helo_name}};\
39466 ip=$sender_host_address
39469 When the spf condition has run, it sets up several expansion
39472 .cindex SPF "verification variables"
39474 .vitem &$spf_header_comment$&
39475 .vindex &$spf_header_comment$&
39476 This contains a human-readable string describing the outcome
39477 of the SPF check. You can add it to a custom header or use
39478 it for logging purposes.
39480 .vitem &$spf_received$&
39481 .vindex &$spf_received$&
39482 This contains a complete Received-SPF: header that can be
39483 added to the message. Please note that according to the SPF
39484 draft, this header must be added at the top of the header
39485 list. Please see section 10 on how you can do this.
39487 Note: in case of "Best-guess" (see below), the convention is
39488 to put this string in a header called X-SPF-Guess: instead.
39490 .vitem &$spf_result$&
39491 .vindex &$spf_result$&
39492 This contains the outcome of the SPF check in string form,
39493 one of pass, fail, softfail, none, neutral, permerror or
39496 .vitem &$spf_result_guessed$&
39497 .vindex &$spf_result_guessed$&
39498 This boolean is true only if a best-guess operation was used
39499 and required in order to obtain a result.
39501 .vitem &$spf_smtp_comment$&
39502 .vindex &$spf_smtp_comment$&
39503 This contains a string that can be used in a SMTP response
39504 to the calling party. Useful for "fail".
39508 .cindex SPF "ACL condition"
39509 .cindex ACL "spf_guess condition"
39510 .cindex SPF "best guess"
39511 In addition to SPF, you can also perform checks for so-called
39512 "Best-guess". Strictly speaking, "Best-guess" is not standard
39513 SPF, but it is supported by the same framework that enables SPF
39515 Refer to &url(http://www.openspf.org/FAQ/Best_guess_record)
39516 for a description of what it means.
39518 To access this feature, simply use the spf_guess condition in place
39519 of the spf one. For example:
39522 deny spf_guess = fail
39523 message = $sender_host_address doesn't look trustworthy to me
39526 In case you decide to reject messages based on this check, you
39527 should note that although it uses the same framework, "Best-guess"
39528 is not SPF, and therefore you should not mention SPF at all in your
39531 When the spf_guess condition has run, it sets up the same expansion
39532 variables as when spf condition is run, described above.
39534 Additionally, since Best-guess is not standardized, you may redefine
39535 what "Best-guess" means to you by redefining the main configuration
39536 &%spf_guess%& option.
39537 For example, the following:
39540 spf_guess = v=spf1 a/16 mx/16 ptr ?all
39543 would relax host matching rules to a broader network range.
39546 .cindex SPF "lookup expansion"
39548 A lookup expansion is also available. It takes an email
39549 address as the key and an IP address as the database:
39552 ${lookup {username@domain} spf {ip.ip.ip.ip}}
39555 The lookup will return the same result strings as can appear in
39556 &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp).
39557 Currently, only IPv4 addresses are supported.
39562 . ////////////////////////////////////////////////////////////////////////////
39563 . ////////////////////////////////////////////////////////////////////////////
39565 .chapter "Proxies" "CHAPproxies" &&&
39567 .cindex "proxy support"
39568 .cindex "proxy" "access via"
39570 A proxy is an intermediate system through which communication is passed.
39571 Proxies may provide a security, availability or load-distribution function.
39574 .section "Inbound proxies" SECTproxyInbound
39575 .cindex proxy inbound
39576 .cindex proxy "server side"
39577 .cindex proxy "Proxy protocol"
39578 .cindex "Proxy protocol" proxy
39580 Exim has support for receiving inbound SMTP connections via a proxy
39581 that uses &"Proxy Protocol"& to speak to it.
39582 To include this support, include &"SUPPORT_PROXY=yes"&
39585 It was built on specifications from:
39586 (&url(http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt)).
39587 That URL was revised in May 2014 to version 2 spec:
39588 (&url(http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e)).
39590 The purpose of this facility is so that an application load balancer,
39591 such as HAProxy, can sit in front of several Exim servers
39592 to distribute load.
39593 Exim uses the local protocol communication with the proxy to obtain
39594 the remote SMTP system IP address and port information.
39595 There is no logging if a host passes or
39596 fails Proxy Protocol negotiation, but it can easily be determined and
39597 recorded in an ACL (example is below).
39599 Use of a proxy is enabled by setting the &%hosts_proxy%&
39600 main configuration option to a hostlist; connections from these
39601 hosts will use Proxy Protocol.
39602 Exim supports both version 1 and version 2 of the Proxy Protocol and
39603 automatically determines which version is in use.
39605 The Proxy Protocol header is the first data received on a TCP connection
39606 and is inserted before any TLS-on-connect handshake from the client; Exim
39607 negotiates TLS between Exim-as-server and the remote client, not between
39608 Exim and the proxy server.
39610 The following expansion variables are usable
39611 (&"internal"& and &"external"& here refer to the interfaces
39614 &'proxy_external_address '& IP of host being proxied or IP of remote interface of proxy
39615 &'proxy_external_port '& Port of host being proxied or Port on remote interface of proxy
39616 &'proxy_local_address '& IP of proxy server inbound or IP of local interface of proxy
39617 &'proxy_local_port '& Port of proxy server inbound or Port on local interface of proxy
39618 &'proxy_session '& boolean: SMTP connection via proxy
39620 If &$proxy_session$& is set but &$proxy_external_address$& is empty
39621 there was a protocol error.
39623 Since the real connections are all coming from the proxy, and the
39624 per host connection tracking is done before Proxy Protocol is
39625 evaluated, &%smtp_accept_max_per_host%& must be set high enough to
39626 handle all of the parallel volume you expect per inbound proxy.
39627 With the option set so high, you lose the ability
39628 to protect your server from many connections from one IP.
39629 In order to prevent your server from overload, you
39630 need to add a per connection ratelimit to your connect ACL.
39631 A possible solution is:
39633 # Set max number of connections per host
39635 # Or do some kind of IP lookup in a flat file or database
39636 # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}}
39638 defer message = Too many connections from this IP right now
39639 ratelimit = LIMIT / 5s / per_conn / strict
39644 .section "Outbound proxies" SECTproxySOCKS
39645 .cindex proxy outbound
39646 .cindex proxy "client side"
39647 .cindex proxy SOCKS
39648 .cindex SOCKS proxy
39649 Exim has support for sending outbound SMTP via a proxy
39650 using a protocol called SOCKS5 (defined by RFC1928).
39651 The support can be optionally included by defining SUPPORT_SOCKS=yes in
39654 Use of a proxy is enabled by setting the &%socks_proxy%& option
39655 on an smtp transport.
39656 The option value is expanded and should then be a list
39657 (colon-separated by default) of proxy specifiers.
39658 Each proxy specifier is a list
39659 (space-separated by default) where the initial element
39660 is an IP address and any subsequent elements are options.
39662 Options are a string <name>=<value>.
39663 The list of options is in the following table:
39665 &'auth '& authentication method
39666 &'name '& authentication username
39667 &'pass '& authentication password
39669 &'tmo '& connection timeout
39671 &'weight '& selection bias
39674 More details on each of these options follows:
39677 .cindex authentication "to proxy"
39678 .cindex proxy authentication
39679 &%auth%&: Either &"none"& (default) or &"name"&.
39680 Using &"name"& selects username/password authentication per RFC 1929
39681 for access to the proxy.
39682 Default is &"none"&.
39684 &%name%&: sets the username for the &"name"& authentication method.
39687 &%pass%&: sets the password for the &"name"& authentication method.
39690 &%port%&: the TCP port number to use for the connection to the proxy.
39693 &%tmo%&: sets a connection timeout in seconds for this proxy.
39696 &%pri%&: specifies a priority for the proxy within the list,
39697 higher values being tried first.
39698 The default priority is 1.
39700 &%weight%&: specifies a selection bias.
39701 Within a priority set servers are queried in a random fashion,
39702 weighted by this value.
39703 The default value for selection bias is 1.
39706 Proxies from the list are tried according to their priority
39707 and weight settings until one responds. The timeout for the
39708 overall connection applies to the set of proxied attempts.
39710 .section Logging SECTproxyLog
39711 To log the (local) IP of a proxy in the incoming or delivery logline,
39712 add &"+proxy"& to the &%log_selector%& option.
39713 This will add a component tagged with &"PRX="& to the line.
39715 . ////////////////////////////////////////////////////////////////////////////
39716 . ////////////////////////////////////////////////////////////////////////////
39718 .chapter "Internationalisation" "CHAPi18n" &&&
39719 "Internationalisation""
39720 .cindex internationalisation "email address"
39723 .cindex utf8 "mail name handling"
39725 Exim has support for Internationalised mail names.
39726 To include this it must be built with SUPPORT_I18N and the libidn library.
39727 Standards supported are RFCs 2060, 5890, 6530 and 6533.
39729 If Exim is built with SUPPORT_I18N_2008 (in addition to SUPPORT_I18N, not
39730 instead of it) then IDNA2008 is supported; this adds an extra library
39731 requirement, upon libidn2.
39733 .section "MTA operations" SECTi18nMTA
39734 .cindex SMTPUTF8 "ESMTP option"
39735 The main configuration option &%smtputf8_advertise_hosts%& specifies
39736 a host list. If this matches the sending host and
39737 accept_8bitmime is true (the default) then the ESMTP option
39738 SMTPUTF8 will be advertised.
39740 If the sender specifies the SMTPUTF8 option on a MAIL command
39741 international handling for the message is enabled and
39742 the expansion variable &$message_smtputf8$& will have value TRUE.
39744 The option &%allow_utf8_domains%& is set to true for this
39745 message. All DNS lookups are converted to a-label form
39746 whatever the setting of &%allow_utf8_domains%&
39747 when Exim is built with SUPPORT_I18N.
39749 Both localparts and domain are maintained as the original
39750 UTF-8 form internally; any comparison or regular-expression use will
39751 require appropriate care. Filenames created, eg. by
39752 the appendfile transport, will have UTF-8 names.
39754 HELO names sent by the smtp transport will have any UTF-8
39755 components expanded to a-label form,
39756 and any certificate name checks will be done using the a-label
39759 .cindex log protocol
39760 .cindex SMTPUTF8 logging
39761 .cindex i18n logging
39762 Log lines and Received-by: header lines will acquire a "utf8"
39763 prefix on the protocol element, eg. utf8esmtp.
39765 The following expansion operators can be used:
39767 ${utf8_domain_to_alabel:str}
39768 ${utf8_domain_from_alabel:str}
39769 ${utf8_localpart_to_alabel:str}
39770 ${utf8_localpart_from_alabel:str}
39773 .cindex utf8 "address downconversion"
39774 .cindex i18n "utf8 address downconversion"
39776 may use the following modifier:
39778 control = utf8_downconvert
39779 control = utf8_downconvert/<value>
39781 This sets a flag requiring that addresses are converted to
39782 a-label form before smtp delivery, for use in a
39783 Message Submission Agent context.
39784 If a value is appended it may be:
39786 &`1 `& (default) mandatory downconversion
39787 &`0 `& no downconversion
39788 &`-1 `& if SMTPUTF8 not supported by destination host
39791 If mua_wrapper is set, the utf8_downconvert control
39792 is initially set to -1.
39795 There is no explicit support for VRFY and EXPN.
39796 Configurations supporting these should inspect
39797 &$smtp_command_argument$& for an SMTPUTF8 argument.
39799 There is no support for LMTP on Unix sockets.
39800 Using the "lmtp" protocol option on an smtp transport,
39801 for LMTP over TCP, should work as expected.
39803 There is no support for DSN unitext handling,
39804 and no provision for converting logging from or to UTF-8.
39808 .section "MDA operations" SECTi18nMDA
39809 To aid in constructing names suitable for IMAP folders
39810 the following expansion operator can be used:
39812 ${imapfolder {<string>} {<sep>} {<specials>}}
39815 The string is converted from the charset specified by
39816 the "headers charset" command (in a filter file)
39817 or &%headers_charset%& main configuration option (otherwise),
39819 modified UTF-7 encoding specified by RFC 2060,
39820 with the following exception: All occurrences of <sep>
39821 (which has to be a single character)
39822 are replaced with periods ("."), and all periods and slashes that are not
39823 <sep> and are not in the <specials> string are BASE64 encoded.
39825 The third argument can be omitted, defaulting to an empty string.
39826 The second argument can be omitted, defaulting to "/".
39828 This is the encoding used by Courier for Maildir names on disk, and followed
39829 by many other IMAP servers.
39833 &`${imapfolder {Foo/Bar}} `& yields &`Foo.Bar`&
39834 &`${imapfolder {Foo/Bar}{.}{/}} `& yields &`Foo&&AC8-Bar`&
39835 &`${imapfolder {Räksmörgås}} `& yields &`R&&AOQ-ksm&&APY-rg&&AOU-s`&
39838 Note that the source charset setting is vital, and also that characters
39839 must be representable in UTF-16.
39842 . ////////////////////////////////////////////////////////////////////////////
39843 . ////////////////////////////////////////////////////////////////////////////
39845 .chapter "Events" "CHAPevents" &&&
39849 The events mechanism in Exim can be used to intercept processing at a number
39850 of points. It was originally invented to give a way to do customised logging
39851 actions (for example, to a database) but can also be used to modify some
39852 processing actions.
39854 Most installations will never need to use Events.
39855 The support can be left out of a build by defining DISABLE_EVENT=yes
39856 in &_Local/Makefile_&.
39858 There are two major classes of events: main and transport.
39859 The main configuration option &%event_action%& controls reception events;
39860 a transport option &%event_action%& controls delivery events.
39862 Both options are a string which is expanded when the event fires.
39863 An example might look like:
39864 .cindex logging custom
39866 event_action = ${if eq {msg:delivery}{$event_name} \
39867 {${lookup pgsql {SELECT * FROM record_Delivery( \
39868 '${quote_pgsql:$sender_address_domain}',\
39869 '${quote_pgsql:${lc:$sender_address_local_part}}', \
39870 '${quote_pgsql:$domain}', \
39871 '${quote_pgsql:${lc:$local_part}}', \
39872 '${quote_pgsql:$host_address}', \
39873 '${quote_pgsql:${lc:$host}}', \
39874 '${quote_pgsql:$message_exim_id}')}} \
39878 Events have names which correspond to the point in process at which they fire.
39879 The name is placed in the variable &$event_name$& and the event action
39880 expansion must check this, as it will be called for every possible event type.
39882 The current list of events is:
39884 &`dane:fail after transport `& per connection
39885 &`msg:complete after main `& per message
39886 &`msg:delivery after transport `& per recipient
39887 &`msg:rcpt:host:defer after transport `& per recipient per host
39888 &`msg:rcpt:defer after transport `& per recipient
39889 &`msg:host:defer after transport `& per attempt
39890 &`msg:fail:delivery after transport `& per recipient
39891 &`msg:fail:internal after main `& per recipient
39892 &`tcp:connect before transport `& per connection
39893 &`tcp:close after transport `& per connection
39894 &`tls:cert before both `& per certificate in verification chain
39895 &`smtp:connect after transport `& per connection
39897 New event types may be added in future.
39899 The event name is a colon-separated list, defining the type of
39900 event in a tree of possibilities. It may be used as a list
39901 or just matched on as a whole. There will be no spaces in the name.
39903 The second column in the table above describes whether the event fires
39904 before or after the action is associates with. Those which fire before
39905 can be used to affect that action (more on this below).
39907 The third column in the table above says what section of the configuration
39908 should define the event action.
39910 An additional variable, &$event_data$&, is filled with information varying
39911 with the event type:
39913 &`dane:fail `& failure reason
39914 &`msg:delivery `& smtp confirmation message
39915 &`msg:rcpt:host:defer `& error string
39916 &`msg:rcpt:defer `& error string
39917 &`msg:host:defer `& error string
39918 &`tls:cert `& verification chain depth
39919 &`smtp:connect `& smtp banner
39922 The :defer events populate one extra variable: &$event_defer_errno$&.
39924 For complex operations an ACL expansion can be used in &%event_action%&
39925 however due to the multiple contexts that Exim operates in during
39926 the course of its processing:
39928 variables set in transport events will not be visible outside that
39931 acl_m variables in a server context are lost on a new connection,
39932 and after smtp helo/ehlo/mail/starttls/rset commands
39934 Using an ACL expansion with the logwrite modifier can be
39935 a useful way of writing to the main log.
39937 The expansion of the event_action option should normally
39938 return an empty string. Should it return anything else the
39939 following will be forced:
39941 &`tcp:connect `& do not connect
39942 &`tls:cert `& refuse verification
39943 &`smtp:connect `& close connection
39945 All other message types ignore the result string, and
39946 no other use is made of it.
39948 For a tcp:connect event, if the connection is being made to a proxy
39949 then the address and port variables will be that of the proxy and not
39952 For tls:cert events, if GnuTLS is in use this will trigger only per
39953 chain element received on the connection.
39954 For OpenSSL it will trigger for every chain element including those
39957 . ////////////////////////////////////////////////////////////////////////////
39958 . ////////////////////////////////////////////////////////////////////////////
39960 .chapter "Adding new drivers or lookup types" "CHID13" &&&
39961 "Adding drivers or lookups"
39962 .cindex "adding drivers"
39963 .cindex "new drivers, adding"
39964 .cindex "drivers" "adding new"
39965 The following actions have to be taken in order to add a new router, transport,
39966 authenticator, or lookup type to Exim:
39969 Choose a name for the driver or lookup type that does not conflict with any
39970 existing name; I will use &"newdriver"& in what follows.
39972 Add to &_src/EDITME_& the line:
39974 <&'type'&>&`_NEWDRIVER=yes`&
39976 where <&'type'&> is ROUTER, TRANSPORT, AUTH, or LOOKUP. If the
39977 code is not to be included in the binary by default, comment this line out. You
39978 should also add any relevant comments about the driver or lookup type.
39980 Add to &_src/config.h.defaults_& the line:
39982 #define <type>_NEWDRIVER
39985 Edit &_src/drtables.c_&, adding conditional code to pull in the private header
39986 and create a table entry as is done for all the other drivers and lookup types.
39988 Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop
39989 near the bottom, ranging the &`name_mod`& variable over a list of all lookups.
39990 Add your &`NEWDRIVER`& to that list.
39991 As long as the dynamic module would be named &_newdriver.so_&, you can use the
39992 simple form that most lookups have.
39994 Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&,
39995 &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new
39996 driver or lookup type and add it to the definition of OBJ.
39998 Create &_newdriver.h_& and &_newdriver.c_& in the appropriate sub-directory of
40001 Edit &_scripts/MakeLinks_& and add commands to link the &_.h_& and &_.c_& files
40002 as for other drivers and lookups.
40005 Then all you need to do is write the code! A good way to start is to make a
40006 proforma by copying an existing module of the same type, globally changing all
40007 occurrences of the name, and cutting out most of the code. Note that any
40008 options you create must be listed in alphabetical order, because the tables are
40009 searched using a binary chop procedure.
40011 There is a &_README_& file in each of the sub-directories of &_src_& describing
40012 the interface that is expected.
40017 . ////////////////////////////////////////////////////////////////////////////
40018 . ////////////////////////////////////////////////////////////////////////////
40020 . /////////////////////////////////////////////////////////////////////////////
40021 . These lines are processing instructions for the Simple DocBook Processor that
40022 . Philip Hazel has developed as a less cumbersome way of making PostScript and
40023 . PDFs than using xmlto and fop. They will be ignored by all other XML
40025 . /////////////////////////////////////////////////////////////////////////////
40030 foot_right_recto="&chaptertitle;"
40031 foot_right_verso="&chaptertitle;"
40035 .makeindex "Options index" "option"
40036 .makeindex "Variables index" "variable"
40037 .makeindex "Concept index" "concept"
40040 . /////////////////////////////////////////////////////////////////////////////
40041 . /////////////////////////////////////////////////////////////////////////////