Make verify=helo do the verification on the fly it if was not done
[exim.git] / doc / doc-txt / NewStuff
1 $Cambridge: exim/doc/doc-txt/NewStuff,v 1.61 2005/08/02 15:19:20 ph10 Exp $
3 New Features in Exim
4 --------------------
6 This file contains descriptions of new features that have been added to Exim,
7 but have not yet made it into the main manual (which is most conveniently
8 updated when there is a relatively large batch of changes). The doc/ChangeLog
9 file contains a listing of all changes, including bug fixes.
11 Exim version 4.53
12 -----------------
14 TK/01 Added the "success_on_redirect" address verification option. When an
15 address generates new addresses during routing, Exim will abort
16 verification with "success" when more than one address has been
17 generated, but continue to verify a single new address. The latter
18 does not happen when the new "success_on_redirect" option is set, like
20 require verify = recipient/success_on_redirect/callout=10s
22 In that case, verification will succeed when a router generates a new
23 address.
25 PH/01 Support for SQLite database lookups has been added. This is another
26 query-style lookup, but it is slightly different from the others because
27 a file name is required in addition to the SQL query. This is because an
28 SQLite database is a single file and there is no daemon as in other SQL
29 databases. The interface to Exim requires the name of the file, as an
30 absolute path, to be given at the start of the query. It is separated
31 from the query by white space. This means that the path name cannot
32 contain white space. Here is a lookup expansion example:
34 ${lookup sqlite {/some/thing/sqlitedb \
35 select name from aliases where id='ph10';}}
37 In a list, the syntax is similar. For example:
39 domainlist relay_domains = sqlite;/some/thing/sqlitedb \
40 select * from relays where ip='$sender_host_address';
42 The only character affected by the ${quote_sqlite: operator is a single
43 quote, which it doubles.
45 Note that you must set LOOKUP_SQLITE=yes in Local/Makefile in order to
46 obtain SQLite support, and you will also need to add -lsqlite3 to the
47 EXTRALIBS setting. And of course, you have to install SQLite on your
48 host first.
50 PH/02 The variable $message_id is now deprecated, to be replaced by
51 $message_exim_id, which makes it clearer which ID is being referenced.
53 PH/03 The use of forbid_filter_existstest now also locks out the use of the
54 ${stat: expansion item.
56 PH/04 The IGNOREQUOTA extension to the LMTP protocol is now available in both
57 the lmtp transport and the smtp transport running in LMTP mode. In the
58 lmtp transport there is a new Boolean option called ignore_quota, and in
59 the smtp transport there is a new Boolean option called
60 lmtp_ignore_quota. If either of these options is set TRUE, the string
61 "IGNOREQUOTA" is added to RCPT commands when using the LMTP protocol,
62 provided that the server has advertised support for IGNOREQUOTA in its
63 response to the LHLO command.
65 PH/05 Previously, if "verify = helo" was set in an ACL, the condition was true
66 only if the host matched helo_try_verify_hosts, which caused the
67 verification to occur when the EHLO/HELO command was issued. The ACL just
68 tested the remembered result. Now, if a previous verification attempt has
69 not happened, "verify = helo" does it there and then.
72 Exim version 4.52
73 -----------------
75 TF/01 Support for checking Client SMTP Authorization has been added. CSA is a
76 system which allows a site to advertise which machines are and are not
77 permitted to send email. This is done by placing special SRV records in
78 the DNS, which are looked up using the client's HELO domain. At this
79 time CSA is still an Internet-Draft.
81 Client SMTP Authorization checks are performed by the ACL condition
82 verify=csa. This will fail if the client is not authorized. If there is
83 a DNS problem, or if no valid CSA SRV record is found, or if the client
84 is authorized, the condition succeeds. These three cases can be
85 distinguished using the expansion variable $csa_status, which can take
86 one of the values "fail", "defer", "unknown", or "ok". The condition
87 does not itself defer because that would be likely to cause problems
88 for legitimate email.
90 The error messages produced by the CSA code include slightly more
91 detail. If $csa_status is "defer" this may be because of problems
92 looking up the CSA SRV record, or problems looking up the CSA target
93 address record. There are four reasons for $csa_status being "fail":
94 the client's host name is explicitly not authorized; the client's IP
95 address does not match any of the CSA target IP addresses; the client's
96 host name is authorized but it has no valid target IP addresses (e.g.
97 the target's addresses are IPv6 and the client is using IPv4); or the
98 client's host name has no CSA SRV record but a parent domain has
99 asserted that all subdomains must be explicitly authorized.
101 The verify=csa condition can take an argument which is the domain to
102 use for the DNS query. The default is verify=csa/$sender_helo_name.
104 This implementation includes an extension to CSA. If the query domain
105 is an address literal such as [], or if it is a bare IP
106 address, Exim will search for CSA SRV records in the reverse DNS as if
107 the HELO domain was e.g. Therefore it is
108 meaningful to say, for example, verify=csa/$sender_host_address - in
109 fact, this is the check that Exim performs if the client does not say
110 HELO. This extension can be turned off by setting the main
111 configuration option dns_csa_use_reverse = false.
113 If a CSA SRV record is not found for the domain itself, then a search
114 is performed through its parent domains for a record which might be
115 making assertions about subdomains. The maximum depth of this search is
116 limited using the main configuration option dns_csa_search_limit, which
117 takes the value 5 by default. Exim does not look for CSA SRV records in
118 a top level domain, so the default settings handle HELO domains as long
119 as seven ( which encompasses the
120 vast majority of legitimate HELO domains.
122 The dnsdb lookup also has support for CSA. Although dnsdb already
123 supports SRV lookups, this is not sufficient because of the extra
124 parent domain search behaviour of CSA, and (as with PTR lookups)
125 dnsdb also turns IP addresses into lookups in the reverse DNS space.
126 The result of ${lookup dnsdb {csa=$sender_helo_name} } has two
127 space-separated fields: an authorization code and a target host name.
128 The authorization code can be "Y" for yes, "N" for no, "X" for explicit
129 authorization required but absent, or "?" for unknown.
131 PH/01 The amount of output produced by the "make" process has been reduced,
132 because the compile lines are often rather long, making it all pretty
133 unreadable. The new style is along the lines of the 2.6 Linux kernel:
134 just a short line for each module that is being compiled or linked.
135 However, it is still possible to get the full output, by calling "make"
136 like this:
138 FULLECHO='' make -e
140 The value of FULLECHO defaults to "@", the flag character that suppresses
141 command reflection in "make". When you ask for the full output, it is
142 given in addition to the the short output.
144 TF/02 There have been two changes concerned with submission mode:
146 Until now submission mode always left the return path alone, whereas
147 locally-submitted messages from untrusted users have the return path
148 fixed to the user's email address. Submission mode now fixes the return
149 path to the same address as is used to create the Sender: header. If
150 /sender_retain is specified then both the Sender: header and the return
151 path are left alone.
153 Note that the changes caused by submission mode take effect after the
154 predata ACL. This means that any sender checks performed before the
155 fix-ups will use the untrusted sender address specified by the user, not
156 the trusted sender address specified by submission mode. Although this
157 might be slightly unexpected, it does mean that you can configure ACL
158 checks to spot that a user is trying to spoof another's address, for
159 example.
161 There is also a new /name= option for submission mode which allows you
162 to specify the user's full name to be included in the Sender: header.
163 For example:
165 accept authenticated = *
166 control = submission/name=${lookup {$authenticated_id} \
167 lsearch {/etc/exim/namelist} }
169 The namelist file contains entries like
171 fanf: Tony Finch
173 And the resulting Sender: header looks like
175 Sender: Tony Finch <>
177 TF/03 The control = fakereject ACL modifier now has a fakedefer counterpart,
178 which works in exactly the same way except it causes a fake SMTP 450
179 response after the message data instead of a fake SMTP 550 response.
180 You must take care when using fakedefer because it will cause messages
181 to be duplicated when the sender retries. Therefore you should not use
182 fakedefer if the message will be delivered normally.
184 TF/04 There is a new ratelimit ACL condition which can be used to measure
185 and control the rate at which clients can send email. This is more
186 powerful than the existing smtp_ratelimit_* options, because those
187 options only control the rate of commands in a single SMTP session,
188 whereas the new ratelimit condition works across all connections
189 (concurrent and sequential) to the same host.
191 The syntax of the ratelimit condition is:
193 ratelimit = <m> / <p> / <options> / <key>
195 If the average client sending rate is less than m messages per time
196 period p then the condition is false, otherwise it is true.
198 The parameter p is the smoothing time constant, in the form of an Exim
199 time interval e.g. 8h for eight hours. A larger time constant means it
200 takes Exim longer to forget a client's past behaviour. The parameter m is
201 the maximum number of messages that a client can send in a fast burst. By
202 increasing both m and p but keeping m/p constant, you can allow a client
203 to send more messages in a burst without changing its overall sending
204 rate limit. Conversely, if m and p are both small then messages must be
205 sent at an even rate.
207 The key is used to look up the data used to calcluate the client's
208 average sending rate. This data is stored in a database maintained by
209 Exim in its spool directory alongside the retry database etc. For
210 example, you can limit the sending rate of each authenticated user,
211 independent of the computer they are sending from, by setting the key
212 to $authenticated_id. The default key is $sender_host_address.
213 Internally, Exim includes the smoothing constant p and the options in
214 the lookup key because they alter the meaning of the stored data.
215 This is not true for the limit m, so you can alter the configured
216 maximum rate and Exim will still remember clients' past behaviour,
217 but if you alter the other ratelimit parameters Exim will effectively
218 forget their past behaviour.
220 Each ratelimit condition can have up to two options. The first option
221 specifies what Exim measures the rate of, and the second specifies how
222 Exim handles excessively fast clients.
224 The per_mail option means that it measures the client's rate of sending
225 messages. This is the default if none of the per_* options is specified.
227 The per_conn option means that it measures the client's connection rate.
229 The per_byte option limits the sender's email bandwidth. Note that it
230 is best to use this option in the DATA ACL; if it is used in an earlier
231 ACL it relies on the SIZE parameter on the MAIL command, which may be
232 inaccurate or completely missing. You can follow the limit m in the
233 configuration with K, M, or G to specify limits in kilobytes,
234 megabytes, or gigabytes respectively.
236 The per_cmd option means that Exim recomputes the rate every time the
237 condition is processed, which can be used to limit the SMTP command rate.
238 The alias per_rcpt is provided for use in the RCPT ACL instead of per_cmd
239 to make it clear that the effect is to limit the rate at which recipients
240 are accepted. Note that in this case the rate limiting engine will see a
241 message with many recipients as a large high-speed burst.
243 If a client's average rate is greater than the maximum, the rate
244 limiting engine can react in two possible ways, depending on the
245 presence of the strict or leaky options. This is independent of the
246 other counter-measures (e.g. rejecting the message) that may be
247 specified by the rest of the ACL. The default mode is leaky, which
248 avoids a sender's over-aggressive retry rate preventing it from getting
249 any email through.
251 The strict option means that the client's recorded rate is always
252 updated. The effect of this is that Exim measures the client's average
253 rate of attempts to send email, which can be much higher than the
254 maximum. If the client is over the limit it will be subjected to
255 counter-measures until it slows down below the maximum rate.
257 The leaky option means that the client's recorded rate is not updated
258 if it is above the limit. The effect of this is that Exim measures the
259 client's average rate of successfully sent email, which cannot be
260 greater than the maximum. If the client is over the limit it will
261 suffer some counter-measures, but it will still be able to send email
262 at the configured maximum rate, whatever the rate of its attempts.
264 As a side-effect, the ratelimit condition will set the expansion
265 variables $sender_rate containing the client's computed rate,
266 $sender_rate_limit containing the configured value of m, and
267 $sender_rate_period containing the configured value of p.
269 Exim's other ACL facilities are used to define what counter-measures
270 are taken when the rate limit is exceeded. This might be anything from
271 logging a warning (e.g. while measuring existing sending rates in order
272 to define our policy), through time delays to slow down fast senders,
273 up to rejecting the message. For example,
275 # Log all senders' rates
276 warn
277 ratelimit = 0 / 1h / strict
278 log_message = \
279 Sender rate $sender_rate > $sender_rate_limit / $sender_rate_period
281 # Slow down fast senders
282 warn
283 ratelimit = 100 / 1h / per_rcpt / strict
284 delay = ${eval: 10 * ($sender_rate - $sender_rate_limit) }
286 # Keep authenticated users under control
287 deny
288 ratelimit = 100 / 1d / strict / $authenticated_id
290 # System-wide rate limit
291 defer
292 message = Sorry, too busy. Try again later.
293 ratelimit = 10 / 1s / $primary_hostname
295 # Restrict incoming rate from each host, with a default rate limit
296 # set using a macro and special cases looked up in a table.
297 defer
298 message = Sender rate $sender_rate exceeds \
299 $sender_rate_limit messages per $sender_rate_period
300 ratelimit = ${lookup {$sender_host_address} \
301 cdb {DB/ratelimits.cdb} \
302 {$value} {RATELIMIT} }
304 Warning: if you have a busy server with a lot of ratelimit tests,
305 especially with the per_rcpt option, you may suffer from a performance
306 bottleneck caused by locking on the ratelimit hints database. Apart from
307 making your ACLs less complicated, you can reduce the problem by using a
308 RAM disk for Exim's hints directory, /var/spool/exim/db/. However this
309 means that Exim will lose its hints data after a reboot (including retry
310 hints, the callout cache, and ratelimit data).
312 TK/01 Added an 'spf' lookup type that will return an SPF result for a given
313 email address (the key) and an IP address (the database):
315 ${lookup {} spf{}}
317 The lookup will return the same result strings as they can appear in
318 $spf_result (pass,fail,softfail,neutral,none,err_perm,err_temp). The
319 lookup is armored in EXPERIMENTAL_SPF. Currently, only IPv4 addresses
320 are supported.
322 Patch submitted by Chris Webb <>.
324 PH/02 There's a new verify callout option, "fullpostmaster", which first acts
325 as "postmaster" and checks the recipient <postmaster@domain>. If that
326 fails, it tries just <postmaster>, without a domain, in accordance with
327 the specification in RFC 2821.
329 PH/03 The action of the auto_thaw option has been changed. It no longer applies
330 to frozen bounce messages.
332 TK/02 There are two new expansion items to help with the implementation of
333 the BATV "prvs" scheme in an Exim configuration:
336 ${prvs {<ADDRESS>}{<KEY>}{[KEYNUM]}}
338 The "prvs" expansion item takes three arguments: A qualified RFC2821
339 email address, a key and an (optional) key number. All arguments are
340 expanded before being used, so it is easily possible to lookup a key
341 and key number using the address as the lookup key. The key number is
342 optional and defaults to "0". The item will expand to a "prvs"-signed
343 email address, to be typically used with the "return_path" option on
344 a smtp transport. The decision if BATV should be used with a given
345 sender/recipient pair should be done on router level, to avoid having
346 to set "max_rcpt = 1" on the transport.
349 ${prvscheck {<ADDRESS>}{<SECRET>}{<RETURN_STRING>}}
351 The "prvscheck" expansion item takes three arguments. Argument 1 is
352 expanded first. When the expansion does not yield a SYNTACTICALLY
353 valid "prvs"-scheme address, the whole "prvscheck" item expands to
354 the empty string. If <ADDRESS> is a "prvs"-encoded address after
355 expansion, two expansion variables are set up:
357 $prvscheck_address Contains the "prvs"-decoded version of
358 the address from argument 1.
360 $prvscheck_keynum Contains the key number extracted from
361 the "prvs"-address in argument 1.
363 These two variables can be used in the expansion code of argument 2
364 to retrieve the <SECRET>. The VALIDITY of the "prvs"-signed address
365 is then checked. The result is stored in yet another expansion
366 variable:
368 $prvscheck_result Contains the result of a "prvscheck"
369 expansion: Unset (the empty string) for
370 failure, "1" for success.
372 The "prvscheck" expansion expands to the empty string if <ADDRESS>
373 is not a SYNTACTICALLY valid "prvs"-scheme address. Otherwise,
374 argument 3 defines what "prvscheck" expands to: If argument 3
375 is the empty string, "prvscheck" expands to the decoded version
376 of the address (no matter if it is CRYPTOGRAPHICALLY valid or not).
377 If argument 3 expands to a non-empty string, "prvscheck" expands
378 to that string.
381 Usage example
382 -------------
384 Macro:
386 PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs WHERE \
387 sender='${quote_mysql:$prvscheck_address}'}{$value}}
391 # Bounces: drop unsigned addresses for BATV senders
392 deny message = This address does not send an unsigned reverse path.
393 senders = :
394 recipients = +batv_recipients
396 # Bounces: In case of prvs-signed address, check signature.
397 deny message = Invalid reverse path signature.
398 senders = :
399 condition = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}{1}}
400 !condition = $prvscheck_result
402 Top-Level Router:
404 batv_redirect:
405 driver = redirect
406 data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}{}}
408 Transport (referenced by router that makes decision if
409 BATV is applicable):
411 external_smtp_batv:
412 driver = smtp
413 return_path = ${prvs {$return_path} \
414 {${lookup mysql{SELECT \
415 secret FROM batv_prvs WHERE \
416 sender='${quote_mysql:$sender_address}'} \
417 {$value}fail}}}
419 PH/04 There are two new options that control the retrying done by the daemon
420 at startup when it cannot immediately bind a socket (typically because
421 the socket is already in use). The default values reproduce what were
422 built-in constants previously: daemon_startup_retries defines the number
423 of retries after the first failure (default 9); daemon_startup_sleep
424 defines the length of time to wait between retries (default 30s).
426 PH/05 There is now a new ${if condition called "match_ip". It is similar to
427 match_domain, etc. It must be followed by two argument strings. The first
428 (after expansion) must be an IP address or an empty string. The second
429 (after expansion) is a restricted host list that can match only an IP
430 address, not a host name. For example:
432 ${if match_ip{$sender_host_address}{}{...}{...}}
434 The specific types of host list item that are permitted in the list are
435 shown below. Consult the manual section on host lists for further
436 details.
438 . An IP address, optionally with a CIDR mask.
440 . A single asterisk matches any IP address.
442 . An empty item matches only if the IP address is empty. This could be
443 useful for testing for a locally submitted message or one from specific
444 hosts in a single test such as
446 ${if match_ip{$sender_host_address}{:}{...}{...}}
448 where the first item in the list is the empty string.
450 . The item @[] matches any of the local host's interface addresses.
452 . Lookups are assumed to be "net-" style lookups, even if "net-" is not
453 specified. Thus, the following are equivalent:
455 ${if match_ip{$sender_host_address}{lsearch;/some/file}...
456 ${if match_ip{$sender_host_address}{net-lsearch;/some/file}...
458 You do need to specify the "net-" prefix if you want to specify a
459 specific address mask, for example, by using "net24-".
461 PH/06 The "+all" debug selector used to set the flags for all possible output;
462 it is something that people tend to use semi-automatically when
463 generating debug output for me or for the list. However, by including
464 "+memory", an awful lot of output that is very rarely of interest was
465 generated. I have changed this so that "+all" no longer includes
466 "+memory". However, "-all" still turns everything off.
469 Version 4.51
470 ------------
472 PH/01 The format in which GnuTLS parameters are written to the gnutls-param
473 file in the spool directory has been changed. This change has been made
474 to alleviate problems that some people had with the generation of the
475 parameters by Exim when /dev/random was exhausted. In this situation,
476 Exim would hang until /dev/random acquired some more entropy.
478 The new code exports and imports the DH and RSA parameters in PEM
479 format. This means that the parameters can be generated externally using
480 the certtool command that is part of GnuTLS.
482 To replace the parameters with new ones, instead of deleting the file
483 and letting Exim re-create it, you can generate new parameters using
484 certtool and, when this has been done, replace Exim's cache file by
485 renaming. The relevant commands are something like this:
487 # rm -f new.params
488 # touch new.params
489 # chown exim:exim new.params
490 # chmod 0400 new.params
491 # certtool --generate-privkey --bits 512 >new.params
492 # echo "" >>new.params
493 # certtool --generate-dh-params --bits 1024 >> new.params
494 # mv new.params params
496 If Exim never has to generate the parameters itself, the possibility of
497 stalling is removed.
499 PH/02 A new expansion item for dynamically loading and calling a locally-
500 written C function is now provided, if Exim is compiled with
504 set in Local/Makefile. The facility is not included by default (a
505 suitable error is given if you try to use it when it is not there.)
507 If you enable EXPAND_DLFUNC, you should also be aware of the new redirect
508 router option forbid_filter_dlfunc. If you have unprivileged users on
509 your system who are permitted to create filter files, you might want to
510 set forbid_filter_dlfunc=true in the appropriate router, to stop them
511 using ${dlfunc to run code within Exim.
513 You load and call an external function like this:
515 ${dlfunc{/some/file}{function}{arg1}{arg2}...}
517 Once loaded, Exim remembers the dynamically loaded object so that it
518 doesn't reload the same object file in the same Exim process (but of
519 course Exim does start new processes frequently).
521 There may be from zero to eight arguments to the function. When compiling
522 a local function that is to be called in this way, local_scan.h should be
523 included. The Exim variables and functions that are defined by that API
524 are also available for dynamically loaded functions. The function itself
525 must have the following type:
527 int dlfunction(uschar **yield, int argc, uschar *argv[])
529 Where "uschar" is a typedef for "unsigned char" in local_scan.h. The
530 function should return one of the following values:
532 OK Success. The string that is placed in "yield" is put into
533 the expanded string that is being built.
535 FAIL A non-forced expansion failure occurs, with the error
536 message taken from "yield", if it is set.
538 FAIL_FORCED A forced expansion failure occurs, with the error message
539 taken from "yield" if it is set.
541 ERROR Same as FAIL, except that a panic log entry is written.
543 When compiling a function that is to be used in this way with gcc,
544 you need to add -shared to the gcc command. Also, in the Exim build-time
545 configuration, you must add -export-dynamic to EXTRALIBS.
547 TF/01 $received_time is a new expansion variable containing the time and date
548 as a number of seconds since the start of the Unix epoch when the
549 current message was received.
551 PH/03 There is a new value for RADIUS_LIB_TYPE that can be set in
552 Local/Makefile. It is RADIUSCLIENTNEW, and it requests that the new API,
553 in use from radiusclient 0.4.0 onwards, be used. It does not appear to be
554 possible to detect the different versions automatically.
556 PH/04 There is a new option called acl_not_smtp_mime that allows you to scan
557 MIME parts in non-SMTP messages. It operates in exactly the same way as
558 acl_smtp_mime
560 PH/05 It is now possible to redefine a macro within the configuration file.
561 The macro must have been previously defined within the configuration (or
562 an included file). A definition on the command line using the -D option
563 causes all definitions and redefinitions within the file to be ignored.
564 In other words, -D overrides any values that are set in the file.
565 Redefinition is specified by using '==' instead of '='. For example:
567 MAC1 = initial value
568 ...
569 MAC1 == updated value
571 Redefinition does not alter the order in which the macros are applied to
572 the subsequent lines of the configuration file. It is still the same
573 order in which the macros were originally defined. All that changes is
574 the macro's value. Redefinition makes it possible to accumulate values.
575 For example:
577 MAC1 = initial value
578 ...
579 MAC1 == MAC1 and something added
581 This can be helpful in situations where the configuration file is built
582 from a number of other files.
584 PH/06 Macros may now be defined or redefined between router, transport,
585 authenticator, or ACL definitions, as well as in the main part of the
586 configuration. They may not, however, be changed within an individual
587 driver or ACL, or in the local_scan, retry, or rewrite sections of the
588 configuration.
590 PH/07 $acl_verify_message is now set immediately after the failure of a
591 verification in an ACL, and so is available in subsequent modifiers. In
592 particular, the message can be preserved by coding like this:
594 warn !verify = sender
595 set acl_m0 = $acl_verify_message
597 Previously, $acl_verify_message was set only while expanding "message"
598 and "log_message" when a very denied access.
600 PH/08 The redirect router has two new options, sieve_useraddress and
601 sieve_subaddress. These are passed to a Sieve filter to specify the :user
602 and :subaddress parts of an address. Both options are unset by default.
603 However, when a Sieve filter is run, if sieve_useraddress is unset, the
604 entire original local part (including any prefix or suffix) is used for
605 :user. An unset subaddress is treated as an empty subaddress.
607 PH/09 Quota values can be followed by G as well as K and M.
609 PH/10 $message_linecount is a new variable that contains the total number of
610 lines in the header and body of the message. Compare $body_linecount,
611 which is the count for the body only. During the DATA and
612 content-scanning ACLs, $message_linecount contains the number of lines
613 received. Before delivery happens (that is, before filters, routers, and
614 transports run) the count is increased to include the Received: header
615 line that Exim standardly adds, and also any other header lines that are
616 added by ACLs. The blank line that separates the message header from the
617 body is not counted. Here is an example of the use of this variable in a
620 deny message = Too many lines in message header
621 condition = \
622 ${if <{250}{${eval: $message_linecount - $body_linecount}}}
624 In the MAIL and RCPT ACLs, the value is zero because at that stage the
625 message has not yet been received.
627 PH/11 In a ${run expansion, the variable $value (which contains the standard
628 output) is now also usable in the "else" string.
630 PH/12 In a pipe transport, although a timeout while waiting for the pipe
631 process to complete was treated as a delivery failure, a timeout while
632 writing the message to the pipe was logged, but erroneously treated as a
633 successful delivery. Such timeouts include transport filter timeouts. For
634 consistency with the overall process timeout, these timeouts are now
635 treated as errors, giving rise to delivery failures by default. However,
636 there is now a new Boolean option for the pipe transport called
637 timeout_defer, which, if set TRUE, converts the failures into defers for
638 both kinds of timeout. A transport filter timeout is now identified in
639 the log output.
642 Version 4.50
643 ------------
645 The documentation is up-to-date for the 4.50 release.
647 ****