-This file contains descriptions of new features that have been added to Exim,
-but have not yet made it into the main manual (which is most conveniently
-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 4.52
------------------
-
-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.
-
- 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} }
-
-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>.
-
-
-Version 4.51
+This file contains descriptions of new features that have been added to Exim.
+Before a formal release, there may be quite a lot of detail so that people can
+test from the snapshots or the CVS before the documentation is updated. Once
+the documentation is updated, this file is reduced to a short list.
+
+
+Version 4.64
+------------
+
+ 1. ACL variables can now be given arbitrary names, as long as they start with
+ "acl_c" or "acl_m" (for connection variables and message variables), are at
+ least six characters long, with the sixth character being either a digit or
+ an underscore. The rest of the name can contain alphanumeric characters and
+ underscores. This is a compatible change because the old set of variables
+ such as acl_m12 are a subset of the allowed names. There may now be any
+ number of ACL variables. For example:
+
+ set acl_c13 = value for original ACL variable
+ set acl_c13b = whatever
+ set acl_m_foo = something
+
+ What happens if a syntactically valid but undefined ACL variable is
+ referenced depends on the setting of the strict_acl_vars option. If it is
+ false (the default), an empty string is substituted; if it is true, an
+ error is generated. This affects all ACL variables, including the "old"
+ ones such as acl_c4. (Previously there wasn't the concept of an undefined
+ ACL variable.)
+
+ The implementation has been done in such a way that spool files containing
+ ACL variable settings written by previous releases of Exim are compatible
+ and can be read by the new release. If only the original numeric names are
+ used, spool files written by the new release can be read by earlier
+ releases.
+
+ 2. There is a new ACL modifier called log_reject_target. It makes it possible
+ to specify which logs are used for messages about ACL rejections. Its
+ argument is a list of words which can be "main", "reject", or "panic". The
+ default is "main:reject". The list may be empty, in which case a rejection
+ is not logged at all. For example, this ACL fragment writes no logging
+ information when access is denied:
+
+ deny <some conditions>
+ log_reject_target =
+
+ The modifier can be used in SMTP and non-SMTP ACLs. It applies to both
+ permanent and temporary rejections.
+
+ 3. There is a new authenticator called "dovecot". This is an interface to the
+ authentication facility of the Dovecot POP/IMAP server, which can support a
+ number of authentication methods. If you are using Dovecot to authenticate
+ POP/IMAP clients, it might be helpful to use the same mechanisms for SMTP
+ authentication. This is a server authenticator only. The only option is
+ server_socket, which must specify the socket which is the interface to
+ Dovecot authentication. The public_name option must specify an
+ authentication mechanism that Dovecot is configured to support. You can
+ have several authenticators for different mechanisms. For example:
+
+ dovecot_plain:
+ driver = dovecot
+ public_name = PLAIN
+ server_name = /var/run/dovecot/auth-client
+ server_setid = $auth1
+
+ dovecot_ntlm:
+ driver = dovecot
+ public_name = NTLM
+ server_name = /var/run/dovecot/auth-client
+ server_setid = $auth1
+
+ If the SMTP connection is encrypted, or if $sender_host_address is equal to
+ $interface_address (that is, the connection is local), the "secured" option
+ is passed in the Dovecot authentication command. If, for a TLS connection,
+ a client certificate has been verified, the "valid-client-cert" option is
+ passed.
+
+ 4. The variable $message_headers_raw provides a concatenation of all the
+ messages's headers without any decoding. This is in contrast to
+ $message_headers, which does RFC2047 decoding on the header contents.
+
+ 5. In a DNS black list, when the facility for restricting the matching IP
+ values is used, the text from the TXT record that is set in $dnslist_text
+ may not reflect the true reason for rejection. This happens when lists are
+ merged and the IP address in the A record is used to distinguish them;
+ unfortunately there is only one TXT record. One way round this is not to
+ use merged lists, but that can be inefficient because it requires multiple
+ DNS lookups where one would do in the vast majority of cases when the host
+ of interest is not on any of the lists.
+
+ A less inefficient way of solving this problem has now been implemented. If
+ two domain names, comma-separated, are given, the second is used first to
+ do an initial check, making use of any IP value restrictions that are set.
+ If there is a match, the first domain is used, without any IP value
+ restrictions, to get the TXT record. As a byproduct of this, there is also
+ a check that the IP being tested is indeed on the first list. The first
+ domain is the one that is put in $dnslist_domain. For example:
+
+ reject message = rejected because $sender_ip_address is blacklisted \
+ at $dnslist_domain\n$dnslist_text
+ dnslists = sbl.spamhaus.org,sbl-xbl.spamhaus.org=127.0.0.2 : \
+ dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
+
+ For the first blacklist item, this starts by doing a lookup in
+ sbl-xbl.spamhaus.org and testing for a 127.0.0.2 return. If there is a
+ match, it then looks in sbl.spamhaus.org, without checking the return
+ value, and as long as something is found, it looks for the corresponding
+ TXT record. If there is no match in sbl-xbl.spamhaus.org, nothing more is
+ done. The second blacklist item is processed similarly.
+
+ If you are interested in more than one merged list, the same list must be
+ given several times, but because the results of the DNS lookups are cached,
+ the DNS calls themselves are not repeated. For example:
+
+ reject dnslists = http.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.2 : \
+ socks.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.3 : \
+ misc.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.4 : \
+ dul.dnsbl.sorbs.net,dnsbl.sorbs.net=127.0.0.10
+
+ In this case there is a lookup in dnsbl.sorbs.net, and if none of the IP
+ values matches (or if no record is found), this is the only lookup that is
+ done. Only if there is a match is one of the more specific lists consulted.
+
+ 6. All authenticators now have a server_condition option. Previously, only
+ plaintext had this, and this has not changed: it must be set to the
+ authenticator as a server. For the others, if server_condition is set, it
+ is expanded if authentication is successful, and treated exactly as it is
+ in plaintext. This can serve as a means of adding authorization to an
+ authenticator.
+
+ 7. There is a new command-line option called -Mset. It is useful only in
+ conjunction with -be (that is, when testing string expansions). It must be
+ followed by a message id; Exim loads the given message from its spool
+ before doing the expansions, thus setting message-specific variables such
+ as $message_size and the header variables. The $recipients variable is
+ available. This feature is provided to make it easier to test expansions
+ that make use of these variables. However, Exim must be called by an admin
+ user when -Mset is used.
+
+ 8. Another similar new command-line option is called -bem. It operates like
+ -be except that it must be followed by the name of a file. For example:
+
+ exim -bem /tmp/testmessage
+
+ The file is read as a message (as if receiving a locally-submitted non-SMTP
+ message) before any of the test expansions are done. Thus, message-specific
+ variables such as $message_size and $h_from: are available. However, no
+ Received: header is added to the message. If the -t option is set,
+ recipients are read from the headers in the normal way, and are shown in
+ the $recipients variable. Note that recipients cannot be given on the
+ command line, because further arguments are taken as strings to expand
+ (just like -be).
+
+ 9. When an address is delayed because of a 4xx response to a RCPT command, it
+ is now the combination of sender and recipient that is delayed in
+ subsequent queue runs until its retry time is reached. You can revert to
+ the previous behavious, that is, delay the recipient independent of the
+ sender, by setting address_retry_include_sender=false in the smtp
+ transport. However, this can lead to problems with servers that regularly
+ issue 4xx responses to RCPT commands.
+
+10. Unary negation and the bitwise logical operators and, or, xor, not, and
+ shift, have been added to the eval: and eval10: expansion items. These
+ items may now contain arithmetic operators (plus, minus, times, divide,
+ remainder, negate), bitwise operators (and, or, xor, not, shift), and
+ parentheses. All operations are carried out using signed integer
+ arithmetic. Operator priorities are as in C, namely:
+
+ (highest) not, negate
+ times, divide, remainder
+ plus, minus
+ shift-left, shift-right
+ and
+ xor
+ (lowest) or
+
+ Binary operators with the same priority are evaluated from left to right.
+ For example:
+
+ ${eval:1+1} yields 2
+ ${eval:1+2*3} yields 7
+ ${eval:(1+2)*3} yields 9
+ ${eval:2+42%5} yields 4
+ ${eval:0xc&5} yields 4
+ ${eval:0xc|5} yields 13
+ ${eval:0xc^5} yields 9
+ ${eval:0xc>>1} yields 6
+ ${eval:0xc<<1} yields 24
+ ${eval:~255&0x1234} yields 4608
+ ${eval:-(~255&0x1234)} yields -4608
+
+11. The variables $interface_address and $interface_port have been renamed
+ as $received_ip_address and $received_port, to make it clear that they
+ relate to message reception rather than delivery. (The old names remain
+ available for compatibility.)
+
+12. The "message" modifier can now be used on acl verbs to vary the message
+ that is sent when an SMTP command. For example, in a RCPT ACL you could
+ have:
+
+ accept <some conditions>
+ message = OK, I'll allow you through today
+
+ Previously, this message modifier would have had no effect whatsoever.
+
+ IMPORTANT: The new behaviour applies to "accept" (and "discard") only if
+ there is no occurrence of "endpass" in the statement. If "endpass" is
+ present, the behaviour reverts to the old case, where "message" applies to
+ rejection. This is for backwards compatibility.
+
+ It is always possible to rewrite ACL statements so that "endpass" is not
+ needed (and indeed it is no longer used in the default configuration, and
+ is somewhat not recommended nowadays because it causes confusion.)
+
+ It is now generally true that the "message" modifier sets up a text string
+ that is expanded and used as a response message if the current statement
+ terminates the ACL. The expansion happens at the time Exim decides that the
+ ACL is to end, not at the time it processes "message". If the expansion
+ fails, or generates an empty string, the modifier is ignored.
+
+ For ACLs that are triggered by SMTP commands, the message is returned as
+ part of the SMTP response. In this situation, the message may begin with an
+ overriding SMTP response code, optionally followed by an "extended response
+ code". However, the first digit of the supplied response code must be the
+ same as would be sent by default. A panic occurs if it is not. For the
+ predata ACL, note that the default success code is 354, not 2xx.
+
+ However, notwithstanding the previous paragraph, for the QUIT ACL, unlike
+ the others, the message modifier cannot override the 221 response code.
+
+ In the case of the "connect" ACL, accepting with a message modifier
+ overrides the value of smtp_banner.
+
+ The ACL test specified by acl_smtp_helo happens when the client issues the
+ HELO or EHLO commands, after the tests specified by helo_accept_junk_hosts,
+ helo_allow_chars and helo(_try)_verify_hosts. An acceptance message
+ modifier for EHLO/HELO may not contain more than one line (it will be
+ truncated at the first newline and a panic logged), and it cannot affect
+ the EHLO options.
+
+
+
+Version 4.63
+------------
+
+1. There is a new Boolean option called filter_prepend_home for the redirect
+ router.
+
+2. There is a new acl, set by acl_not_smtp_start, which is run right at the
+ start of receiving a non-SMTP message, before any of the message has been
+ read.
+
+3. When an SMTP error message is specified in a "message" modifier in an ACL,
+ or in a :fail: or :defer: message in a redirect router, Exim now checks the
+ start of the message for an SMTP error code.
+
+4. There is a new parameter for LDAP lookups called "referrals", which takes
+ one of the settings "follow" (the default) or "nofollow".
+
+5. Version 20070721.2 of exipick now included, offering these new options:
+ --reverse
+ After all other sorting options have bee processed, reverse order
+ before displaying messages (-R is synonym).
+ --random
+ Randomize order of matching messages before displaying.
+ --size
+ Instead of displaying the matching messages, display the sum
+ of their sizes.
+ --sort <variable>[,<variable>...]
+ Before displaying matching messages, sort the messages according to
+ each messages value for each variable.
+ --not
+ Negate the value for every test (returns inverse output from the
+ same criteria without --not).
+
+
+Version 4.62
git://git.exim.org / users / heiko / exim.git / blobdiff