-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
-
-
-Exim version 4.52
------------------
-
-TF/01 Support for checking Client SMTP Authorization has been added. CSA is a
- system which allows a site to advertise which machines are and are not
- permitted to send email. This is done by placing special SRV records in
- the DNS, which are looked up using the client's HELO domain. At this
- time CSA is still an Internet-Draft.
-
- Client SMTP Authorization checks are performed by the ACL condition
- verify=csa. This will fail if the client is not authorized. If there is
- a DNS problem, or if no valid CSA SRV record is found, or if the client
- is authorized, the condition succeeds. These three cases can be
- distinguished using the expansion variable $csa_status, which can take
- one of the values "fail", "defer", "unknown", or "ok". The condition
- does not itself defer because that would be likely to cause problems
- for legitimate email.
-
- The error messages produced by the CSA code include slightly more
- detail. If $csa_status is "defer" this may be because of problems
- looking up the CSA SRV record, or problems looking up the CSA target
- address record. There are four reasons for $csa_status being "fail":
- the client's host name is explicitly not authorized; the client's IP
- address does not match any of the CSA target IP addresses; the client's
- host name is authorized but it has no valid target IP addresses (e.g.
- the target's addresses are IPv6 and the client is using IPv4); or the
- client's host name has no CSA SRV record but a parent domain has
- asserted that all subdomains must be explicitly authorized.
-
- The verify=csa condition can take an argument which is the domain to
- use for the DNS query. The default is verify=csa/$sender_helo_name.
-
- This implementation includes an extension to CSA. If the query domain
- is an address literal such as [192.0.2.95], or if it is a bare IP
- address, Exim will search for CSA SRV records in the reverse DNS as if
- the HELO domain was e.g. 95.2.0.192.in-addr.arpa. Therefore it is
- meaningful to say, for example, verify=csa/$sender_host_address - in
- fact, this is the check that Exim performs if the client does not say
- HELO. This extension can be turned off by setting the main
- configuration option dns_csa_use_reverse = false.
-
- If a CSA SRV record is not found for the domain itself, then a search
- is performed through its parent domains for a record which might be
- making assertions about subdomains. The maximum depth of this search is
- limited using the main configuration option dns_csa_search_limit, which
- takes the value 5 by default. Exim does not look for CSA SRV records in
- a top level domain, so the default settings handle HELO domains as long
- as seven (hostname.five.four.three.two.one.com) which encompasses the
- vast majority of legitimate HELO domains.
-
- The dnsdb lookup also has support for CSA. Although dnsdb already
- supports SRV lookups, this is not sufficient because of the extra
- parent domain search behaviour of CSA, and (as with PTR lookups)
- dnsdb also turns IP addresses into lookups in the reverse DNS space.
- The result of ${lookup dnsdb {csa=$sender_helo_name} } has two
- space-separated fields: an authorization code and a target host name.
- The authorization code can be "Y" for yes, "N" for no, "X" for explicit
- authorization required but absent, or "?" for unknown.
-
-PH/01 The amount of output produced by the "make" process has been reduced,
- because the compile lines are often rather long, making it all pretty
- unreadable. The new style is along the lines of the 2.6 Linux kernel:
- just a short line for each module that is being compiled or linked.
- However, it is still possible to get the full output, by calling "make"
- like this:
-
- FULLECHO='' make -e
-
- The value of FULLECHO defaults to "@", the flag character that suppresses
- command reflection in "make". When you ask for the full output, it is
- given in addition to the the short output.
-
-TF/02 There have been two changes concerned with submission mode:
-
- Until now submission mode always left the return path alone, whereas
- locally-submitted messages from untrusted users have the return path
- fixed to the user's email address. Submission mode now fixes the return
- path to the same address as is used to create the Sender: header. If
- /sender_retain is specified then both the Sender: header and the return
- path are left alone.
-
- Note that the changes caused by submission mode take effect after the
- predata ACL. This means that any sender checks performed before the
- fix-ups will use the untrusted sender address specified by the user, not
- the trusted sender address specified by submission mode. Although this
- might be slightly unexpected, it does mean that you can configure ACL
- checks to spot that a user is trying to spoof another's address, for
- example.
-
- There is also a new /name= option for submission mode which allows you
- to specify the user's full name to be included in the Sender: header.
- For example:
-
- accept authenticated = *
- control = submission/name=${lookup {$authenticated_id} \
- lsearch {/etc/exim/namelist} }
-
- The namelist file contains entries like
-
- fanf: Tony Finch
-
- And the resulting Sender: header looks like
-
- Sender: Tony Finch <fanf@exim.org>
-
-TF/03 The control = fakereject ACL modifier now has a fakedefer counterpart,
- which works in exactly the same way except it causes a fake SMTP 450
- response after the message data instead of a fake SMTP 550 response.
- You must take care when using fakedefer because it will cause messages
- 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 calcluate 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 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 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_limit / $sender_rate_period
-
- # Slow down fast senders
- warn
- ratelimit = 100 / 1h / per_rcpt / strict
- delay = ${eval: 10 * ($sender_rate - $sender_rate_limit) }
-
- # 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 $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:
+Version 4.70
+------------
+
+ 1. Preliminary SPF Best Guess support. Documentation for this is in
+ experimental-spec.txt.
+
+
+Version 4.68
+------------
+
+ 1. The body_linecount and body_zerocount C variables are now exported in the
+ local_scan API.
+
+ 2. When a dnslists lookup succeeds, the key that was looked up is now placed
+ in $dnslist_matched. When the key is an IP address, it is not reversed in
+ this variable (though it is, of course, in the actual lookup). In simple
+ cases, for example:
+
+ deny dnslists = spamhaus.example
+
+ the key is also available in another variable (in this case,
+ $sender_host_address). In more complicated cases, however, this is not
+ true. For example, using a data lookup might generate a dnslists lookup
+ like this:
+
+ deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|...
+
+ If this condition succeeds, the value in $dnslist_matched might be
+ 192.168.6.7 (for example).
+
+ 3. Authenticators now have a client_condition option. When Exim is running as
+ a client, it skips an authenticator whose client_condition expansion yields
+ "0", "no", or "false". This can be used, for example, to skip plain text
+ authenticators when the connection is not encrypted by a setting such as:
+
+ client_condition = ${if !eq{$tls_cipher}{}}
+
+ Note that the 4.67 documentation states that $tls_cipher contains the
+ cipher used for incoming messages. In fact, during SMTP delivery, it
+ contains the cipher used for the delivery. The same is true for
+ $tls_peerdn.
+
+ 4. There is now a -Mvc <message-id> option, which outputs a copy of the
+ message to the standard output, in RFC 2822 format. The option can be used
+ only by an admin user.
+
+ 5. There is now a /noupdate option for the ratelimit ACL condition. It
+ computes the rate and checks the limit as normal, but it does not update
+ the saved data. This means that, in relevant ACLs, it is possible to lookup
+ the existence of a specified (or auto-generated) ratelimit key without
+ incrementing the ratelimit counter for that key.
+
+ In order for this to be useful, another ACL entry must set the rate
+ for the same key somewhere (otherwise it will always be zero).
+
+ Example:
+
+ acl_check_connect:
+ # Read the rate; if it doesn't exist or is below the maximum
+ # we update it below
+ deny ratelimit = 100 / 5m / strict / noupdate
+ log_message = RATE: $sender_rate / $sender_rate_period \
+ (max $sender_rate_limit)
+
+ [... some other logic and tests...]
+
+ warn ratelimit = 100 / 5m / strict / per_cmd
+ log_message = RATE UPDATE: $sender_rate / $sender_rate_period \
+ (max $sender_rate_limit)
+ condition = ${if le{$sender_rate}{$sender_rate_limit}}
+
+ accept
+
+ 6. The variable $max_received_linelength contains the number of bytes in the
+ longest line that was received as part of the message, not counting the
+ line termination character(s).
+
+ 7. Host lists can now include +ignore_defer and +include_defer, analagous to
+ +ignore_unknown and +include_unknown. These options should be used with
+ care, probably only in non-critical host lists such as whitelists.
+
+ 8. There's a new option called queue_only_load_latch, which defaults true.
+ If set false when queue_only_load is greater than zero, Exim re-evaluates
+ the load for each incoming message in an SMTP session. Otherwise, once one
+ message is queued, the remainder are also.
+
+ 9. There is a new ACL, specified by smtp_notquit_acl, which is run in most
+ cases when an SMTP session ends without sending QUIT. However, when Exim
+ itself is is bad trouble, such as being unable to write to its log files,
+ this ACL is not run, because it might try to do things (such as write to
+ log files) that make the situation even worse.
+
+ Like the QUIT ACL, this new ACL is provided to make it possible to gather
+ statistics. Whatever it returns (accept or deny) is immaterial. The "delay"
+ modifier is forbidden in this ACL.
+
+ When the NOTQUIT ACL is running, the variable $smtp_notquit_reason is set
+ to a string that indicates the reason for the termination of the SMTP
+ connection. The possible values are:
+
+ acl-drop Another ACL issued a "drop" command
+ bad-commands Too many unknown or non-mail commands
+ command-timeout Timeout while reading SMTP commands
+ connection-lost The SMTP connection has been lost
+ data-timeout Timeout while reading message data
+ local-scan-error The local_scan() function crashed
+ local-scan-timeout The local_scan() function timed out
+ signal-exit SIGTERM or SIGINT
+ synchronization-error SMTP synchronization error
+ tls-failed TLS failed to start
+
+ In most cases when an SMTP connection is closed without having received
+ QUIT, Exim sends an SMTP response message before actually closing the
+ connection. With the exception of acl-drop, the default message can be
+ overridden by the "message" modifier in the NOTQUIT ACL. In the case of a
+ "drop" verb in another ACL, it is the message from the other ACL that is
+ used.
+
+10. For MySQL and PostgreSQL lookups, it is now possible to specify a list of
+ servers with individual queries. This is done by starting the query with
+ "servers=x:y:z;", where each item in the list may take one of two forms:
+
+ (1) If it is just a host name, the appropriate global option (mysql_servers
+ or pgsql_servers) is searched for a host of the same name, and the
+ remaining parameters (database, user, password) are taken from there.
+
+ (2) If it contains any slashes, it is taken as a complete parameter set.
+
+ The list of servers is used in exactly the same was as the global list.
+ Once a connection to a server has happened and a query has been
+ successfully executed, processing of the lookup ceases.
+
+ This feature is intended for use in master/slave situations where updates
+ are occurring, and one wants to update a master rather than a slave. If the
+ masters are in the list for reading, you might have:
+
+ mysql_servers = slave1/db/name/pw:slave2/db/name/pw:master/db/name/pw
+
+ In an updating lookup, you could then write
+
+ ${lookup mysql{servers=master; UPDATE ...}
+
+ If, on the other hand, the master is not to be used for reading lookups:
+
+ pgsql_servers = slave1/db/name/pw:slave2/db/name/pw
+
+ you can still update the master by
+
+ ${lookup pgsql{servers=master/db/name/pw; UPDATE ...}
git://git.exim.org / users / jgh / exim.git / blobdiff