-$Cambridge: exim/doc/doc-txt/NewStuff,v 1.44 2005/05/23 15:44:06 fanf2 Exp $
+$Cambridge: exim/doc/doc-txt/NewStuff,v 1.76 2005/10/03 13:25:32 ph10 Exp $
New Features in Exim
--------------------
updated when there is a relatively large batch of changes). The doc/ChangeLog
file contains a listing of all changes, including bug fixes.
+Exim version 4.54
+-----------------
+
+There was a problem with 4.52/TF/02 in that a "name=" option on control=
+submission terminated at the next slash, thereby not allowing for slashes in
+the name. This has been changed so that "name=" takes the rest of the string as
+its data. It must therefore be the last option.
+
+
+
+Exim version 4.53
+-----------------
+
+TK/01 Added the "success_on_redirect" address verification option. When an
+ address generates new addresses during routing, Exim will abort
+ verification with "success" when more than one address has been
+ generated, but continue to verify a single new address. The latter
+ does not happen when the new "success_on_redirect" option is set, like
+
+ require verify = recipient/success_on_redirect/callout=10s
+
+ In that case, verification will succeed when a router generates a new
+ address.
+
+PH/01 Support for SQLite database lookups has been added. This is another
+ query-style lookup, but it is slightly different from the others because
+ a file name is required in addition to the SQL query. This is because an
+ SQLite database is a single file and there is no daemon as in other SQL
+ databases. The interface to Exim requires the name of the file, as an
+ absolute path, to be given at the start of the query. It is separated
+ from the query by white space. This means that the path name cannot
+ contain white space. Here is a lookup expansion example:
+
+ ${lookup sqlite {/some/thing/sqlitedb \
+ select name from aliases where id='ph10';}}
+
+ In a list, the syntax is similar. For example:
+
+ domainlist relay_domains = sqlite;/some/thing/sqlitedb \
+ select * from relays where ip='$sender_host_address';
+
+ The only character affected by the ${quote_sqlite: operator is a single
+ quote, which it doubles.
+
+ The SQLite library handles multiple simultaneous accesses to the database
+ internally. Multiple readers are permitted, but only one process can
+ update at once. Attempts to access the database while it is being updated
+ are rejected after a timeout period, during which the SQLite library
+ waits for the lock to be released. In Exim, the default timeout is set
+ to 5 seconds, but it can be changed by means of the sqlite_lock_timeout
+ option.
+
+ Note that you must set LOOKUP_SQLITE=yes in Local/Makefile in order to
+ obtain SQLite support, and you will also need to add -lsqlite3 to the
+ EXTRALIBS setting. And of course, you have to install SQLite on your
+ host first.
+
+PH/02 The variable $message_id is now deprecated, to be replaced by
+ $message_exim_id, which makes it clearer which ID is being referenced.
+
+PH/03 The use of forbid_filter_existstest now also locks out the use of the
+ ${stat: expansion item.
+
+PH/04 The IGNOREQUOTA extension to the LMTP protocol is now available in both
+ the lmtp transport and the smtp transport running in LMTP mode. In the
+ lmtp transport there is a new Boolean option called ignore_quota, and in
+ the smtp transport there is a new Boolean option called
+ lmtp_ignore_quota. If either of these options is set TRUE, the string
+ "IGNOREQUOTA" is added to RCPT commands when using the LMTP protocol,
+ provided that the server has advertised support for IGNOREQUOTA in its
+ response to the LHLO command.
+
+PH/05 Previously, if "verify = helo" was set in an ACL, the condition was true
+ only if the host matched helo_try_verify_hosts, which caused the
+ verification to occur when the EHLO/HELO command was issued. The ACL just
+ tested the remembered result. Now, if a previous verification attempt has
+ not happened, "verify = helo" does it there and then.
+
+PH/06 It is now possible to specify a port number along with a host name or
+ IP address in the list of hosts defined in the manualroute or
+ queryprogram routers, fallback_hosts, or the "hosts" option of the smtp
+ transport. These all override any port specification on the transport.
+ The relatively standard syntax of using a colon separator has been
+ adopted, but there are some gotchas that need attention:
+
+ * In all these lists of hosts, colon is the default separator, so either
+ the colon that specifies a port must be doubled, or the separator must
+ be changed. The following two examples have the same effect:
+
+ fallback_hosts = host1.tld::1225 : host2.tld::1226
+ fallback_hosts = <; host1.tld:1225 ; host2.tld:1226
+
+ * When IPv6 addresses are involved, it gets worse, because they contain
+ colons of their own. To make this case easier, it is permitted to
+ enclose an IP address (either v4 or v6) in square brackets if a port
+ number follows. Here's an example from a manualroute router:
+
+ route_list = * "</ [10.1.1.1]:1225 / [::1]:1226"
+
+ If the "/MX" feature is to be used as well as a port specifier, the port
+ must come last. For example:
+
+ route_list = * dom1.tld/mx::1225
+
+PH/07 $smtp_command_argument is now set for all SMTP commands, not just the
+ non-message ones. This makes it possible to inspect the complete command
+ for RCPT commands, for example. But see also PH/45 below.
+
+PH/08 The ${eval expansion now supports % as a "remainder" operator.
+
+PH/09 There is a new ACL condition "verify = not_blind". It checks that there
+ are no blind (bcc) recipients in the message. Every envelope recipient
+ must appear either in a To: header line or in a Cc: header line for this
+ condition to be true. Local parts are checked case-sensitively; domains
+ are checked case-insensitively. If Resent-To: or Resent-Cc: header lines
+ exist, they are also checked. This condition can be used only in a DATA
+ or non-SMTP ACL.
+
+ There are, of course, many legitimate messages that make use of blind
+ (bcc) recipients. This check should not be used on its own for blocking
+ messages.
+
+PH/10 There is a new ACL control called "suppress_local_fixups". This applies
+ to locally submitted (non TCP/IP) messages, and is the complement of
+ "control = submission". It disables the fixups that are normally applied
+ to locally-submitted messages. Specifically:
+
+ (a) Any Sender: header line is left alone (in this respect, it's a
+ dynamic version of local_sender_retain).
+
+ (b) No Message-ID:, From:, or Date: headers are added.
+
+ (c) There is no check that From: corresponds to the actual sender.
+
+ This feature may be useful when a remotely-originated message is
+ accepted, passed to some scanning program, and then re-submitted for
+ delivery. It means that all four possibilities can now be specified:
+
+ (1) Locally submitted, fixups applies: the default.
+ (2) Locally submitted, no fixups applied: use control =
+ suppress_local_fixups.
+ (3) Remotely submitted, no fixups applied: the default.
+ (4) Remotely submitted, fixups applied: use control = submission.
+
+PH/11 There is a new log selector, "unknown_in_list", which provokes a log
+ entry when the result of a list match is failure because a DNS lookup
+ failed.
+
+PH/12 There is a new variable called $smtp_command which contains the full SMTP
+ command (compare $smtp_command_argument - see PH/07 above). This makes it
+ possible to distinguish between HELO and EHLO, and also between things
+ like "MAIL FROM:<>" and "MAIL FROM: <>".
+
+TF/01 There's a new script in util/ratelimit.pl which extracts sending
+ rates from log files, to assist with choosing appropriate settings
+ when deploying the ratelimit ACL condition.
+
+PH/13 A new letter, "H", is available in retry parameter sets. It is similar
+ to "G" (geometric increasing time intervals), except that the interval
+ before the next retry is randomized. Each time, the previous interval is
+ multiplied by the factor in order to get a maximum for the next interval.
+ The mininum interval is the first argument of the parameter, and an
+ actual interval is chosen randomly between them. Such a rule has been
+ found to be helpful in cluster configurations when all the members of the
+ cluster restart at once, and may synchronize their queue processing
+ times.
+
+PH/14 The options never_users, trusted_users, admin_groups, and trusted_groups
+ are now expanded when the configuration file is read.
+
Exim version 4.52
-----------------
to be duplicated when the sender retries. Therefore you should not use
fakedefer if the message will be delivered normally.
+TF/04 There is a new ratelimit ACL condition which can be used to measure
+ and control the rate at which clients can send email. This is more
+ powerful than the existing smtp_ratelimit_* options, because those
+ options only control the rate of commands in a single SMTP session,
+ whereas the new ratelimit condition works across all connections
+ (concurrent and sequential) to the same host.
+
+ The syntax of the ratelimit condition is:
+
+ ratelimit = <m> / <p> / <options> / <key>
+
+ If the average client sending rate is less than m messages per time
+ period p then the condition is false, otherwise it is true.
+
+ The parameter p is the smoothing time constant, in the form of an Exim
+ time interval e.g. 8h for eight hours. A larger time constant means it
+ takes Exim longer to forget a client's past behaviour. The parameter m is
+ the maximum number of messages that a client can send in a fast burst. By
+ increasing both m and p but keeping m/p constant, you can allow a client
+ to send more messages in a burst without changing its overall sending
+ rate limit. Conversely, if m and p are both small then messages must be
+ sent at an even rate.
+
+ The key is used to look up the data used to calculate the client's
+ average sending rate. This data is stored in a database maintained by
+ Exim in its spool directory alongside the retry database etc. For
+ example, you can limit the sending rate of each authenticated user,
+ independent of the computer they are sending from, by setting the key
+ to $authenticated_id. The default key is $sender_host_address.
+ Internally, Exim includes the smoothing constant p and the options in
+ the lookup key because they alter the meaning of the stored data.
+ This is not true for the limit m, so you can alter the configured
+ maximum rate and Exim will still remember clients' past behaviour,
+ but if you alter the other ratelimit parameters Exim will effectively
+ forget their past behaviour.
+
+ Each ratelimit condition can have up to two options. The first option
+ specifies what Exim measures the rate of, and the second specifies how
+ Exim handles excessively fast clients. The options are separated by a
+ slash, like the other parameters.
+
+ The per_mail option means that it measures the client's rate of sending
+ messages. This is the default if none of the per_* options is specified.
+
+ The per_conn option means that it measures the client's connection rate.
+
+ The per_byte option limits the sender's email bandwidth. Note that it
+ is best to use this option in the DATA ACL; if it is used in an earlier
+ ACL it relies on the SIZE parameter on the MAIL command, which may be
+ inaccurate or completely missing. You can follow the limit m in the
+ configuration with K, M, or G to specify limits in kilobytes,
+ megabytes, or gigabytes respectively.
+
+ The per_cmd option means that Exim recomputes the rate every time the
+ condition is processed, which can be used to limit the SMTP command rate.
+ The alias per_rcpt is provided for use in the RCPT ACL instead of per_cmd
+ to make it clear that the effect is to limit the rate at which recipients
+ are accepted. Note that in this case the rate limiting engine will see a
+ message with many recipients as a large high-speed burst.
+
+ If a client's average rate is greater than the maximum, the rate
+ limiting engine can react in two possible ways, depending on the
+ presence of the strict or leaky options. This is independent of the
+ other counter-measures (e.g. rejecting the message) that may be
+ specified by the rest of the ACL. The default mode is leaky, which
+ avoids a sender's over-aggressive retry rate preventing it from getting
+ any email through.
+
+ The strict option means that the client's recorded rate is always
+ updated. The effect of this is that Exim measures the client's average
+ rate of attempts to send email, which can be much higher than the
+ maximum. If the client is over the limit it will be subjected to
+ counter-measures until it slows down below the maximum rate. The
+ smoothing period determines the time it takes for a high sending rate
+ to decay exponentially to 37% of its peak value, which means that you
+ can work out the time (the number of smoothing periods) that a client
+ is subjected to counter-measures after an over-limit burst with the
+ formula ln(peakrate/maxrate).
+
+ The leaky option means that the client's recorded rate is not updated
+ if it is above the limit. The effect of this is that Exim measures the
+ client's average rate of successfully sent email, which cannot be
+ greater than the maximum. If the client is over the limit it will
+ suffer some counter-measures, but it will still be able to send email
+ at the configured maximum rate, whatever the rate of its attempts.
+
+ As a side-effect, the ratelimit condition will set the expansion
+ variables $sender_rate containing the client's computed rate,
+ $sender_rate_limit containing the configured value of m, and
+ $sender_rate_period containing the configured value of p.
+
+ Exim's other ACL facilities are used to define what counter-measures
+ are taken when the rate limit is exceeded. This might be anything from
+ logging a warning (e.g. while measuring existing sending rates in order
+ to define our policy), through time delays to slow down fast senders,
+ up to rejecting the message. For example,
+
+ # Log all senders' rates
+ warn
+ ratelimit = 0 / 1h / strict
+ log_message = Sender rate $sender_rate / $sender_rate_period
+
+ # Slow down fast senders
+ warn
+ ratelimit = 100 / 1h / per_rcpt / strict
+ delay = ${eval: $sender_rate - $sender_rate_limit }s
+
+ # Keep authenticated users under control
+ deny
+ ratelimit = 100 / 1d / strict / $authenticated_id
+
+ # System-wide rate limit
+ defer
+ message = Sorry, too busy. Try again later.
+ ratelimit = 10 / 1s / $primary_hostname
+
+ # Restrict incoming rate from each host, with a default rate limit
+ # set using a macro and special cases looked up in a table.
+ defer
+ message = Sender rate exceeds $sender_rate_limit \
+ messages per $sender_rate_period
+ ratelimit = ${lookup {$sender_host_address} \
+ cdb {DB/ratelimits.cdb} \
+ {$value} {RATELIMIT} }
+
+ Warning: if you have a busy server with a lot of ratelimit tests,
+ especially with the per_rcpt option, you may suffer from a performance
+ bottleneck caused by locking on the ratelimit hints database. Apart from
+ making your ACLs less complicated, you can reduce the problem by using a
+ RAM disk for Exim's hints directory, /var/spool/exim/db/. However this
+ means that Exim will lose its hints data after a reboot (including retry
+ hints, the callout cache, and ratelimit data).
+
+TK/01 Added an 'spf' lookup type that will return an SPF result for a given
+ email address (the key) and an IP address (the database):
+
+ ${lookup {tom@duncanthrax.net} spf{217.115.139.137}}
+
+ The lookup will return the same result strings as they can appear in
+ $spf_result (pass,fail,softfail,neutral,none,err_perm,err_temp). The
+ lookup is armored in EXPERIMENTAL_SPF. Currently, only IPv4 addresses
+ are supported.
+
+ Patch submitted by Chris Webb <chris@arachsys.com>.
+
+PH/02 There's a new verify callout option, "fullpostmaster", which first acts
+ as "postmaster" and checks the recipient <postmaster@domain>. If that
+ fails, it tries just <postmaster>, without a domain, in accordance with
+ the specification in RFC 2821.
+
+PH/03 The action of the auto_thaw option has been changed. It no longer applies
+ to frozen bounce messages.
+
+TK/02 There are two new expansion items to help with the implementation of
+ the BATV "prvs" scheme in an Exim configuration:
+
+
+ ${prvs {<ADDRESS>}{<KEY>}{[KEYNUM]}}
+
+ The "prvs" expansion item takes three arguments: A qualified RFC2821
+ email address, a key and an (optional) key number. All arguments are
+ expanded before being used, so it is easily possible to lookup a key
+ and key number using the address as the lookup key. The key number is
+ optional and defaults to "0". The item will expand to a "prvs"-signed
+ email address, to be typically used with the "return_path" option on
+ a smtp transport. The decision if BATV should be used with a given
+ sender/recipient pair should be done on router level, to avoid having
+ to set "max_rcpt = 1" on the transport.
+
+
+ ${prvscheck {<ADDRESS>}{<SECRET>}{<RETURN_STRING>}}
+
+ The "prvscheck" expansion item takes three arguments. Argument 1 is
+ expanded first. When the expansion does not yield a SYNTACTICALLY
+ valid "prvs"-scheme address, the whole "prvscheck" item expands to
+ the empty string. If <ADDRESS> is a "prvs"-encoded address after
+ expansion, two expansion variables are set up:
+
+ $prvscheck_address Contains the "prvs"-decoded version of
+ the address from argument 1.
+
+ $prvscheck_keynum Contains the key number extracted from
+ the "prvs"-address in argument 1.
+
+ These two variables can be used in the expansion code of argument 2
+ to retrieve the <SECRET>. The VALIDITY of the "prvs"-signed address
+ is then checked. The result is stored in yet another expansion
+ variable:
+
+ $prvscheck_result Contains the result of a "prvscheck"
+ expansion: Unset (the empty string) for
+ failure, "1" for success.
+
+ The "prvscheck" expansion expands to the empty string if <ADDRESS>
+ is not a SYNTACTICALLY valid "prvs"-scheme address. Otherwise,
+ argument 3 defines what "prvscheck" expands to: If argument 3
+ is the empty string, "prvscheck" expands to the decoded version
+ of the address (no matter if it is CRYPTOGRAPHICALLY valid or not).
+ If argument 3 expands to a non-empty string, "prvscheck" expands
+ to that string.
+
+
+ Usage example
+ -------------
+
+ Macro:
+
+ PRVSCHECK_SQL = ${lookup mysql{SELECT secret FROM batv_prvs WHERE \
+ sender='${quote_mysql:$prvscheck_address}'}{$value}}
+
+ RCPT ACL:
+
+ # Bounces: drop unsigned addresses for BATV senders
+ deny message = This address does not send an unsigned reverse path.
+ senders = :
+ recipients = +batv_recipients
+
+ # Bounces: In case of prvs-signed address, check signature.
+ deny message = Invalid reverse path signature.
+ senders = :
+ condition = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}{1}}
+ !condition = $prvscheck_result
+
+ Top-Level Router:
+
+ batv_redirect:
+ driver = redirect
+ data = ${prvscheck {$local_part@$domain}{PRVSCHECK_SQL}{}}
+
+ Transport (referenced by router that makes decision if
+ BATV is applicable):
+
+ external_smtp_batv:
+ driver = smtp
+ return_path = ${prvs {$return_path} \
+ {${lookup mysql{SELECT \
+ secret FROM batv_prvs WHERE \
+ sender='${quote_mysql:$sender_address}'} \
+ {$value}fail}}}
+
+PH/04 There are two new options that control the retrying done by the daemon
+ at startup when it cannot immediately bind a socket (typically because
+ the socket is already in use). The default values reproduce what were
+ built-in constants previously: daemon_startup_retries defines the number
+ of retries after the first failure (default 9); daemon_startup_sleep
+ defines the length of time to wait between retries (default 30s).
+
+PH/05 There is now a new ${if condition called "match_ip". It is similar to
+ match_domain, etc. It must be followed by two argument strings. The first
+ (after expansion) must be an IP address or an empty string. The second
+ (after expansion) is a restricted host list that can match only an IP
+ address, not a host name. For example:
+
+ ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}}
+
+ The specific types of host list item that are permitted in the list are
+ shown below. Consult the manual section on host lists for further
+ details.
+
+ . An IP address, optionally with a CIDR mask.
+
+ . A single asterisk matches any IP address.
+
+ . An empty item matches only if the IP address is empty. This could be
+ useful for testing for a locally submitted message or one from specific
+ hosts in a single test such as
+
+ ${if match_ip{$sender_host_address}{:4.3.2.1:...}{...}{...}}
+
+ where the first item in the list is the empty string.
+
+ . The item @[] matches any of the local host's interface addresses.
+
+ . Lookups are assumed to be "net-" style lookups, even if "net-" is not
+ specified. Thus, the following are equivalent:
+
+ ${if match_ip{$sender_host_address}{lsearch;/some/file}...
+ ${if match_ip{$sender_host_address}{net-lsearch;/some/file}...
+
+ You do need to specify the "net-" prefix if you want to specify a
+ specific address mask, for example, by using "net24-".
+
+PH/06 The "+all" debug selector used to set the flags for all possible output;
+ it is something that people tend to use semi-automatically when
+ generating debug output for me or for the list. However, by including
+ "+memory", an awful lot of output that is very rarely of interest was
+ generated. I have changed this so that "+all" no longer includes
+ "+memory". However, "-all" still turns everything off.
+
Version 4.51
------------
git://git.exim.org / exim.git / blobdiff