doc/doc-txt/NewStuff

   1 $Cambridge: exim/doc/doc-txt/NewStuff,v 1.58 2005/08/01 14:00:34 ph10 Exp $
   2
   3 New Features in Exim
   4 --------------------
   5
   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.
  10
  11 Exim version 4.53
  12 -----------------
  13
  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
  19
  20       require verify = recipient/success_on_redirect/callout=10s
  21
  22       In that case, verification will succeed when a router generates a new
  23       address.
  24
  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:
  33
  34         ${lookup sqlite {/some/thing/sqlitedb \
  35           select name from aliases where id='ph10';}}
  36
  37       In a list, the syntax is similar. For example:
  38
  39         domainlist relay_domains = sqlite;/some/thing/sqlitedb \
  40            select * from relays where ip='$sender_host_address';
  41
  42       The only character affected by the ${quote_sqlite: operator is a single
  43       quote, which it doubles.
  44
  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.
  49
  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.
  52
  53
  54 Exim version 4.52
  55 -----------------
  56
  57 TF/01 Support for checking Client SMTP Authorization has been added. CSA is a
  58       system which allows a site to advertise which machines are and are not
  59       permitted to send email. This is done by placing special SRV records in
  60       the DNS, which are looked up using the client's HELO domain. At this
  61       time CSA is still an Internet-Draft.
  62
  63       Client SMTP Authorization checks are performed by the ACL condition
  64       verify=csa. This will fail if the client is not authorized. If there is
  65       a DNS problem, or if no valid CSA SRV record is found, or if the client
  66       is authorized, the condition succeeds. These three cases can be
  67       distinguished using the expansion variable $csa_status, which can take
  68       one of the values "fail", "defer", "unknown", or "ok". The condition
  69       does not itself defer because that would be likely to cause problems
  70       for legitimate email.
  71
  72       The error messages produced by the CSA code include slightly more
  73       detail. If $csa_status is "defer" this may be because of problems
  74       looking up the CSA SRV record, or problems looking up the CSA target
  75       address record. There are four reasons for $csa_status being "fail":
  76       the client's host name is explicitly not authorized; the client's IP
  77       address does not match any of the CSA target IP addresses; the client's
  78       host name is authorized but it has no valid target IP addresses (e.g.
  79       the target's addresses are IPv6 and the client is using IPv4); or the
  80       client's host name has no CSA SRV record but a parent domain has
  81       asserted that all subdomains must be explicitly authorized.
  82
  83       The verify=csa condition can take an argument which is the domain to
  84       use for the DNS query. The default is verify=csa/$sender_helo_name.
  85
  86       This implementation includes an extension to CSA. If the query domain
  87       is an address literal such as [192.0.2.95], or if it is a bare IP
  88       address, Exim will search for CSA SRV records in the reverse DNS as if
  89       the HELO domain was e.g. 95.2.0.192.in-addr.arpa. Therefore it is
  90       meaningful to say, for example, verify=csa/$sender_host_address - in
  91       fact, this is the check that Exim performs if the client does not say
  92       HELO. This extension can be turned off by setting the main
  93       configuration option dns_csa_use_reverse = false.
  94
  95       If a CSA SRV record is not found for the domain itself, then a search
  96       is performed through its parent domains for a record which might be
  97       making assertions about subdomains. The maximum depth of this search is
  98       limited using the main configuration option dns_csa_search_limit, which
  99       takes the value 5 by default. Exim does not look for CSA SRV records in
 100       a top level domain, so the default settings handle HELO domains as long
 101       as seven (hostname.five.four.three.two.one.com) which encompasses the
 102       vast majority of legitimate HELO domains.
 103
 104       The dnsdb lookup also has support for CSA. Although dnsdb already
 105       supports SRV lookups, this is not sufficient because of the extra
 106       parent domain search behaviour of CSA, and (as with PTR lookups)
 107       dnsdb also turns IP addresses into lookups in the reverse DNS space.
 108       The result of ${lookup dnsdb {csa=$sender_helo_name} } has two
 109       space-separated fields: an authorization code and a target host name.
 110       The authorization code can be "Y" for yes, "N" for no, "X" for explicit
 111       authorization required but absent, or "?" for unknown.
 112
 113 PH/01 The amount of output produced by the "make" process has been reduced,
 114       because the compile lines are often rather long, making it all pretty
 115       unreadable. The new style is along the lines of the 2.6 Linux kernel:
 116       just a short line for each module that is being compiled or linked.
 117       However, it is still possible to get the full output, by calling "make"
 118       like this:
 119
 120         FULLECHO='' make -e
 121
 122       The value of FULLECHO defaults to "@", the flag character that suppresses
 123       command reflection in "make". When you ask for the full output, it is
 124       given in addition to the the short output.
 125
 126 TF/02 There have been two changes concerned with submission mode:
 127
 128       Until now submission mode always left the return path alone, whereas
 129       locally-submitted messages from untrusted users have the return path
 130       fixed to the user's email address. Submission mode now fixes the return
 131       path to the same address as is used to create the Sender: header. If
 132       /sender_retain is specified then both the Sender: header and the return
 133       path are left alone.
 134
 135       Note that the changes caused by submission mode take effect after the
 136       predata ACL. This means that any sender checks performed before the
 137       fix-ups will use the untrusted sender address specified by the user, not
 138       the trusted sender address specified by submission mode. Although this
 139       might be slightly unexpected, it does mean that you can configure ACL
 140       checks to spot that a user is trying to spoof another's address, for
 141       example.
 142
 143       There is also a new /name= option for submission mode which allows you
 144       to specify the user's full name to be included in the Sender: header.
 145       For example:
 146
 147         accept authenticated = *
 148                control = submission/name=${lookup {$authenticated_id} \
 149                                            lsearch {/etc/exim/namelist} }
 150
 151       The namelist file contains entries like
 152
 153         fanf: Tony Finch
 154
 155       And the resulting Sender: header looks like
 156
 157         Sender: Tony Finch <fanf@exim.org>
 158
 159 TF/03 The control = fakereject ACL modifier now has a fakedefer counterpart,
 160       which works in exactly the same way except it causes a fake SMTP 450
 161       response after the message data instead of a fake SMTP 550 response.
 162       You must take care when using fakedefer because it will cause messages
 163       to be duplicated when the sender retries. Therefore you should not use
 164       fakedefer if the message will be delivered normally.
 165
 166 TF/04 There is a new ratelimit ACL condition which can be used to measure
 167       and control the rate at which clients can send email. This is more
 168       powerful than the existing smtp_ratelimit_* options, because those
 169       options only control the rate of commands in a single SMTP session,
 170       whereas the new ratelimit condition works across all connections
 171       (concurrent and sequential) to the same host.
 172
 173       The syntax of the ratelimit condition is:
 174
 175         ratelimit = <m> / <p> / <options> / <key>
 176
 177       If the average client sending rate is less than m messages per time
 178       period p then the condition is false, otherwise it is true.
 179
 180       The parameter p is the smoothing time constant, in the form of an Exim
 181       time interval e.g. 8h for eight hours. A larger time constant means it
 182       takes Exim longer to forget a client's past behaviour. The parameter m is
 183       the maximum number of messages that a client can send in a fast burst. By
 184       increasing both m and p but keeping m/p constant, you can allow a client
 185       to send more messages in a burst without changing its overall sending
 186       rate limit. Conversely, if m and p are both small then messages must be
 187       sent at an even rate.
 188
 189       The key is used to look up the data used to calcluate the client's
 190       average sending rate. This data is stored in a database maintained by
 191       Exim in its spool directory alongside the retry database etc. For
 192       example, you can limit the sending rate of each authenticated user,
 193       independent of the computer they are sending from, by setting the key
 194       to $authenticated_id. The default key is $sender_host_address.
 195       Internally, Exim includes the smoothing constant p and the options in
 196       the lookup key because they alter the meaning of the stored data.
 197       This is not true for the limit m, so you can alter the configured
 198       maximum rate and Exim will still remember clients' past behaviour,
 199       but if you alter the other ratelimit parameters Exim will effectively
 200       forget their past behaviour.
 201
 202       Each ratelimit condition can have up to two options. The first option
 203       specifies what Exim measures the rate of, and the second specifies how
 204       Exim handles excessively fast clients.
 205
 206       The per_mail option means that it measures the client's rate of sending
 207       messages. This is the default if none of the per_* options is specified.
 208
 209       The per_conn option means that it measures the client's connection rate.
 210
 211       The per_byte option limits the sender's email bandwidth. Note that it
 212       is best to use this option in the DATA ACL; if it is used in an earlier
 213       ACL it relies on the SIZE parameter on the MAIL command, which may be
 214       inaccurate or completely missing. You can follow the limit m in the
 215       configuration with K, M, or G to specify limits in kilobytes,
 216       megabytes, or gigabytes respectively.
 217
 218       The per_cmd option means that Exim recomputes the rate every time the
 219       condition is processed, which can be used to limit the SMTP command rate.
 220       The alias per_rcpt is provided for use in the RCPT ACL instead of per_cmd
 221       to make it clear that the effect is to limit the rate at which recipients
 222       are accepted. Note that in this case the rate limiting engine will see a
 223       message with many recipients as a large high-speed burst.
 224
 225       If a client's average rate is greater than the maximum, the rate
 226       limiting engine can react in two possible ways, depending on the
 227       presence of the strict or leaky options. This is independent of the
 228       other counter-measures (e.g. rejecting the message) that may be
 229       specified by the rest of the ACL. The default mode is leaky, which
 230       avoids a sender's over-aggressive retry rate preventing it from getting
 231       any email through.
 232
 233       The strict option means that the client's recorded rate is always
 234       updated. The effect of this is that Exim measures the client's average
 235       rate of attempts to send email, which can be much higher than the
 236       maximum. If the client is over the limit it will be subjected to
 237       counter-measures until it slows down below the maximum rate.
 238
 239       The leaky option means that the client's recorded rate is not updated
 240       if it is above the limit. The effect of this is that Exim measures the
 241       client's average rate of successfully sent email, which cannot be
 242       greater than the maximum. If the client is over the limit it will
 243       suffer some counter-measures, but it will still be able to send email
 244       at the configured maximum rate, whatever the rate of its attempts.
 245
 246       As a side-effect, the ratelimit condition will set the expansion
 247       variables $sender_rate containing the client's computed rate,
 248       $sender_rate_limit containing the configured value of m, and
 249       $sender_rate_period containing the configured value of p.
 250
 251       Exim's other ACL facilities are used to define what counter-measures
 252       are taken when the rate limit is exceeded. This might be anything from
 253       logging a warning (e.g. while measuring existing sending rates in order
 254       to define our policy), through time delays to slow down fast senders,
 255       up to rejecting the message. For example,
 256
 257         # Log all senders' rates
 258         warn
 259           ratelimit = 0 / 1h / strict
 260           log_message = \
 261             Sender rate $sender_rate > $sender_rate_limit / $sender_rate_period
 262
 263         # Slow down fast senders
 264         warn
 265           ratelimit = 100 / 1h / per_rcpt / strict
 266           delay     = ${eval: 10 * ($sender_rate - $sender_rate_limit) }
 267
 268         # Keep authenticated users under control
 269         deny
 270           ratelimit = 100 / 1d / strict / $authenticated_id
 271
 272         # System-wide rate limit
 273         defer
 274           message = Sorry, too busy. Try again later.
 275           ratelimit = 10 / 1s / $primary_hostname
 276
 277         # Restrict incoming rate from each host, with a default rate limit
 278         # set using a macro and special cases looked up in a table.
 279         defer
 280           message = Sender rate $sender_rate exceeds \
 281                     $sender_rate_limit messages per $sender_rate_period
 282           ratelimit = ${lookup {$sender_host_address} \
 283                         cdb {DB/ratelimits.cdb} \
 284                         {$value} {RATELIMIT} }
 285
 286       Warning: if you have a busy server with a lot of ratelimit tests,
 287       especially with the per_rcpt option, you may suffer from a performance
 288       bottleneck caused by locking on the ratelimit hints database. Apart from
 289       making your ACLs less complicated, you can reduce the problem by using a
 290       RAM disk for Exim's hints directory, /var/spool/exim/db/. However this
 291       means that Exim will lose its hints data after a reboot (including retry
 292       hints, the callout cache, and ratelimit data).
 293
 294 TK/01 Added an 'spf' lookup type that will return an SPF result for a given
 295       email address (the key) and an IP address (the database):
 296
 297       ${lookup {tom@duncanthrax.net} spf{217.115.139.137}}
 298
 299       The lookup will return the same result strings as they can appear in
 300       $spf_result (pass,fail,softfail,neutral,none,err_perm,err_temp). The
 301       lookup is armored in EXPERIMENTAL_SPF. Currently, only IPv4 addresses
 302       are supported.
 303
 304       Patch submitted by Chris Webb <chris@arachsys.com>.
 305
 306 PH/02 There's a new verify callout option, "fullpostmaster", which first acts
 307       as "postmaster" and checks the recipient <postmaster@domain>. If that
 308       fails, it tries just <postmaster>, without a domain, in accordance with
 309       the specification in RFC 2821.
 310
 311 PH/03 The action of the auto_thaw option has been changed. It no longer applies
 312       to frozen bounce messages.
 313
 314 TK/02 There are two new expansion items to help with the implementation of
 315       the BATV "prvs" scheme in an Exim configuration:
 316
 317
 318       ${prvs {<ADDRESS>}{<KEY>}{[KEYNUM]}}
 319
 320       The "prvs" expansion item takes three arguments: A qualified RFC2821
 321       email address, a key and an (optional) key number. All arguments are
 322       expanded before being used, so it is easily possible to lookup a key
 323       and key number using the address as the lookup key. The key number is
 324       optional and defaults to "0". The item will expand to a "prvs"-signed
 325       email address, to be typically used with the "return_path" option on
 326       a smtp transport. The decision if BATV should be used with a given
 327       sender/recipient pair should be done on router level, to avoid having
 328       to set "max_rcpt = 1" on the transport.
 329
 330
 331       ${prvscheck {<ADDRESS>}{<SECRET>}{<RETURN_STRING>}}
 332
 333       The "prvscheck" expansion item takes three arguments. Argument 1 is
 334       expanded first. When the expansion does not yield a SYNTACTICALLY
 335       valid "prvs"-scheme address, the whole "prvscheck" item expands to
 336       the empty string. If <ADDRESS> is a "prvs"-encoded address after
 337       expansion, two expansion variables are set up:
 338
 339         $prvscheck_address   Contains the "prvs"-decoded version of
 340                              the address from argument 1.
 341
 342         $prvscheck_keynum    Contains the key number extracted from
 343                              the "prvs"-address in argument 1.
 344
 345       These two variables can be used in the expansion code of argument 2
 346       to retrieve the <SECRET>. The VALIDITY of the "prvs"-signed address
 347       is then checked. The result is stored in yet another expansion
 348       variable:
 349
 350         $prvscheck_result    Contains the result of a "prvscheck"
 351                              expansion: Unset (the empty string) for
 352                              failure, "1" for success.
 353
 354       The "prvscheck" expansion expands to the empty string if <ADDRESS>
 355       is not a SYNTACTICALLY valid "prvs"-scheme address. Otherwise,
 356       argument 3 defines what "prvscheck" expands to: If argument 3
 357       is the empty string, "prvscheck" expands to the decoded version
 358       of the address (no matter if it is CRYPTOGRAPHICALLY valid or not).
 359       If argument 3 expands to a non-empty string, "prvscheck" expands
 360       to that string.
 361
 362
 363       Usage example
 364       -------------
 365
 366       Macro:
 367
 368       PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs WHERE \
 369                       sender='${quote_mysql:$prvscheck_address}'}{$value}}
 370
 371       RCPT ACL:
 372
 373       # Bounces: drop unsigned addresses for BATV senders
 374       deny message = This address does not send an unsigned reverse path.
 375            senders = :
 376            recipients = +batv_recipients
 377
 378       # Bounces: In case of prvs-signed address, check signature.
 379       deny message = Invalid reverse path signature.
 380            senders = :
 381            condition = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}{1}}
 382            !condition = $prvscheck_result
 383
 384       Top-Level Router:
 385
 386       batv_redirect:
 387         driver = redirect
 388         data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}{}}
 389
 390       Transport (referenced by router that makes decision if
 391       BATV is applicable):
 392
 393         external_smtp_batv:
 394           driver = smtp
 395           return_path = ${prvs {$return_path} \
 396                                {${lookup mysql{SELECT \
 397                                secret FROM batv_prvs WHERE \
 398                                sender='${quote_mysql:$sender_address}'} \
 399                            {$value}fail}}}
 400
 401 PH/04 There are two new options that control the retrying done by the daemon
 402       at startup when it cannot immediately bind a socket (typically because
 403       the socket is already in use). The default values reproduce what were
 404       built-in constants previously: daemon_startup_retries defines the number
 405       of retries after the first failure (default 9); daemon_startup_sleep
 406       defines the length of time to wait between retries (default 30s).
 407
 408 PH/05 There is now a new ${if condition called "match_ip". It is similar to
 409       match_domain, etc. It must be followed by two argument strings. The first
 410       (after expansion) must be an IP address or an empty string. The second
 411       (after expansion) is a restricted host list that can match only an IP
 412       address, not a host name. For example:
 413
 414         ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
 415
 416       The specific types of host list item that are permitted in the list are
 417       shown below. Consult the manual section on host lists for further
 418       details.
 419
 420       . An IP address, optionally with a CIDR mask.
 421
 422       . A single asterisk matches any IP address.
 423
 424       . An empty item matches only if the IP address is empty. This could be
 425         useful for testing for a locally submitted message or one from specific
 426         hosts in a single test such as
 427
 428           ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
 429
 430         where the first item in the list is the empty string.
 431
 432       . The item @[] matches any of the local host's interface addresses.
 433
 434       . Lookups are assumed to be "net-" style lookups, even if "net-" is not
 435         specified. Thus, the following are equivalent:
 436
 437           ${if match_ip{$sender_host_address}{lsearch;/some/file}...
 438           ${if match_ip{$sender_host_address}{net-lsearch;/some/file}...
 439
 440         You do need to specify the "net-" prefix if you want to specify a
 441         specific address mask, for example, by using "net24-".
 442
 443 PH/06 The "+all" debug selector used to set the flags for all possible output;
 444       it is something that people tend to use semi-automatically when
 445       generating debug output for me or for the list. However, by including
 446       "+memory", an awful lot of output that is very rarely of interest was
 447       generated. I have changed this so that "+all" no longer includes
 448       "+memory". However, "-all" still turns everything off.
 449
 450
 451 Version 4.51
 452 ------------
 453
 454 PH/01 The format in which GnuTLS parameters are written to the gnutls-param
 455       file in the spool directory has been changed. This change has been made
 456       to alleviate problems that some people had with the generation of the
 457       parameters by Exim when /dev/random was exhausted. In this situation,
 458       Exim would hang until /dev/random acquired some more entropy.
 459
 460       The new code exports and imports the DH and RSA parameters in PEM
 461       format. This means that the parameters can be generated externally using
 462       the certtool command that is part of GnuTLS.
 463
 464       To replace the parameters with new ones, instead of deleting the file
 465       and letting Exim re-create it, you can generate new parameters using
 466       certtool and, when this has been done, replace Exim's cache file by
 467       renaming. The relevant commands are something like this:
 468
 469         # rm -f new.params
 470         # touch new.params
 471         # chown exim:exim new.params
 472         # chmod 0400 new.params
 473         # certtool --generate-privkey --bits 512 >new.params
 474         # echo "" >>new.params
 475         # certtool --generate-dh-params --bits 1024 >> new.params
 476         # mv new.params params
 477
 478       If Exim never has to generate the parameters itself, the possibility of
 479       stalling is removed.
 480
 481 PH/02 A new expansion item for dynamically loading and calling a locally-
 482       written C function is now provided, if Exim is compiled with
 483
 484         EXPAND_DLFUNC=yes
 485
 486       set in Local/Makefile. The facility is not included by default (a
 487       suitable error is given if you try to use it when it is not there.)
 488
 489       If you enable EXPAND_DLFUNC, you should also be aware of the new redirect
 490       router option forbid_filter_dlfunc. If you have unprivileged users on
 491       your system who are permitted to create filter files, you might want to
 492       set forbid_filter_dlfunc=true in the appropriate router, to stop them
 493       using ${dlfunc to run code within Exim.
 494
 495       You load and call an external function like this:
 496
 497         ${dlfunc{/some/file}{function}{arg1}{arg2}...}
 498
 499       Once loaded, Exim remembers the dynamically loaded object so that it
 500       doesn't reload the same object file in the same Exim process (but of
 501       course Exim does start new processes frequently).
 502
 503       There may be from zero to eight arguments to the function. When compiling
 504       a local function that is to be called in this way, local_scan.h should be
 505       included. The Exim variables and functions that are defined by that API
 506       are also available for dynamically loaded functions. The function itself
 507       must have the following type:
 508
 509         int dlfunction(uschar **yield, int argc, uschar *argv[])
 510
 511       Where "uschar" is a typedef for "unsigned char" in local_scan.h. The
 512       function should return one of the following values:
 513
 514       OK            Success. The string that is placed in "yield" is put into
 515                     the expanded string that is being built.
 516
 517       FAIL          A non-forced expansion failure occurs, with the error
 518                     message taken from "yield", if it is set.
 519
 520       FAIL_FORCED   A forced expansion failure occurs, with the error message
 521                     taken from "yield" if it is set.
 522
 523       ERROR         Same as FAIL, except that a panic log entry is written.
 524
 525       When compiling a function that is to be used in this way with gcc,
 526       you need to add -shared to the gcc command. Also, in the Exim build-time
 527       configuration, you must add -export-dynamic to EXTRALIBS.
 528
 529 TF/01 $received_time is a new expansion variable containing the time and date
 530       as a number of seconds since the start of the Unix epoch when the
 531       current message was received.
 532
 533 PH/03 There is a new value for RADIUS_LIB_TYPE that can be set in
 534       Local/Makefile. It is RADIUSCLIENTNEW, and it requests that the new API,
 535       in use from radiusclient 0.4.0 onwards, be used. It does not appear to be
 536       possible to detect the different versions automatically.
 537
 538 PH/04 There is a new option called acl_not_smtp_mime that allows you to scan
 539       MIME parts in non-SMTP messages. It operates in exactly the same way as
 540       acl_smtp_mime
 541
 542 PH/05 It is now possible to redefine a macro within the configuration file.
 543       The macro must have been previously defined within the configuration (or
 544       an included file). A definition on the command line using the -D option
 545       causes all definitions and redefinitions within the file to be ignored.
 546       In other words, -D overrides any values that are set in the file.
 547       Redefinition is specified by using '==' instead of '='. For example:
 548
 549         MAC1 =  initial value
 550         ...
 551         MAC1 == updated value
 552
 553       Redefinition does not alter the order in which the macros are applied to
 554       the subsequent lines of the configuration file. It is still the same
 555       order in which the macros were originally defined. All that changes is
 556       the macro's value. Redefinition makes it possible to accumulate values.
 557       For example:
 558
 559         MAC1 =  initial value
 560         ...
 561         MAC1 == MAC1 and something added
 562
 563       This can be helpful in situations where the configuration file is built
 564       from a number of other files.
 565
 566 PH/06 Macros may now be defined or redefined between router, transport,
 567       authenticator, or ACL definitions, as well as in the main part of the
 568       configuration. They may not, however, be changed within an individual
 569       driver or ACL, or in the local_scan, retry, or rewrite sections of the
 570       configuration.
 571
 572 PH/07 $acl_verify_message is now set immediately after the failure of a
 573       verification in an ACL, and so is available in subsequent modifiers. In
 574       particular, the message can be preserved by coding like this:
 575
 576          warn  !verify = sender
 577                set acl_m0 = $acl_verify_message
 578
 579       Previously, $acl_verify_message was set only while expanding "message"
 580       and "log_message" when a very denied access.
 581
 582 PH/08 The redirect router has two new options, sieve_useraddress and
 583       sieve_subaddress. These are passed to a Sieve filter to specify the :user
 584       and :subaddress parts of an address. Both options are unset by default.
 585       However, when a Sieve filter is run, if sieve_useraddress is unset, the
 586       entire original local part (including any prefix or suffix) is used for
 587       :user. An unset subaddress is treated as an empty subaddress.
 588
 589 PH/09 Quota values can be followed by G as well as K and M.
 590
 591 PH/10 $message_linecount is a new variable that contains the total number of
 592       lines in the header and body of the message. Compare $body_linecount,
 593       which is the count for the body only. During the DATA and
 594       content-scanning ACLs, $message_linecount contains the number of lines
 595       received. Before delivery happens (that is, before filters, routers, and
 596       transports run) the count is increased to include the Received: header
 597       line that Exim standardly adds, and also any other header lines that are
 598       added by ACLs. The blank line that separates the message header from the
 599       body is not counted. Here is an example of the use of this variable in a
 600       DATA ACL:
 601
 602         deny message   = Too many lines in message header
 603              condition = \
 604                ${if <{250}{${eval: $message_linecount - $body_linecount}}}
 605
 606       In the MAIL and RCPT ACLs, the value is zero because at that stage the
 607       message has not yet been received.
 608
 609 PH/11 In a ${run expansion, the variable $value (which contains the standard
 610       output) is now also usable in the "else" string.
 611
 612 PH/12 In a pipe transport, although a timeout while waiting for the pipe
 613       process to complete was treated as a delivery failure, a timeout while
 614       writing the message to the pipe was logged, but erroneously treated as a
 615       successful delivery. Such timeouts include transport filter timeouts. For
 616       consistency with the overall process timeout, these timeouts are now
 617       treated as errors, giving rise to delivery failures by default. However,
 618       there is now a new Boolean option for the pipe transport called
 619       timeout_defer, which, if set TRUE, converts the failures into defers for
 620       both kinds of timeout. A transport filter timeout is now identified in
 621       the log output.
 622
 623
 624 Version 4.50
 625 ------------
 626
 627 The documentation is up-to-date for the 4.50 release.
 628
 629 ****