Exim writes three different logs, referred to as the main log, the reject log, and the panic log:
Every log line starts with a timestamp, in the format shown in this example:
2001-09-16 16:09:47 SMTP connection from [127.0.0.1] closed by QUIT
By default, the timestamps are in the local timezone. There are two ways of changing this:
You can set the timezone option to a different time zone; in particular, if you set
timezone = UTC
the timestamps will be in UTC (aka GMT).
If you set log_timezone true, the time zone is added to the timestamp, for example:
2003-04-25 11:17:07 +0100 Start queue run: pid=12762
The logs may be written to local files, or to syslog, or both. However, it should be noted that many syslog implementations use UDP as a transport, and are therefore unreliable in the sense that messages are not guaranteed to arrive at the loghost, nor is the ordering of messages necessarily maintained. It has also been reported that on large log files (tens of megabytes) you may need to tweak syslog to prevent it syncing the file with each write – on Linux this has been seen to make syslog take 90% plus of CPU time.
The destination for Exim’s logs is configured by setting LOG_FILE_PATH in Local/Makefile or by setting log_file_path in the run time configuration. This latter string is expanded, so it can contain, for example, references to the host name:
log_file_path = /var/log/$primary_hostname/exim_%slog
It is generally advisable, however, to set the string in Local/Makefile rather than at run time, because then the setting is available right from the start of Exim’s execution. Otherwise, if there’s something it wants to log before it has read the configuration file (for example, an error in the configuration file) it will not use the path you want, and may not be able to log at all.
The value of LOG_FILE_PATH or log_file_path is a colon-separated
list, currently limited to at most two items. This is one option where the
facility for changing a list separator may not be used. The list must always be
colon-separated. If an item in the list is “syslog” then syslog is used;
otherwise the item must either be an absolute path, containing %s at the
point where “main”, “reject”, or “panic” is to be inserted, or be empty,
implying the use of a default path.
When Exim encounters an empty item in the list, it searches the list defined by LOG_FILE_PATH, and uses the first item it finds that is neither empty nor “syslog”. This means that an empty item in log_file_path can be used to mean “use the path specified at build time”. It no such item exists, log files are written in the log subdirectory of the spool directory. This is equivalent to the setting:
log_file_path = $spool_directory/log/%slog
If you do not specify anything at build time or run time, that is where the logs are written.
A log file path may also contain %D if datestamped log file names are in
use – see section 48.3 below.
Here are some examples of possible settings:
LOG_FILE_PATH=syslog syslog onlyLOG_FILE_PATH=:syslog syslog and default pathLOG_FILE_PATH=syslog : /usr/log/exim_%s syslog and specified pathLOG_FILE_PATH=/usr/log/exim_%s specified path onlyIf there are more than two paths in the list, the first is used and a panic error is logged.
Some operating systems provide centralized and standardised methods for cycling log files. For those that do not, a utility script called exicyclog is provided (see section 49.6). This renames and compresses the main and reject logs each time it is called. The maximum number of old logs to keep can be set. It is suggested this script is run as a daily cron job.
An Exim delivery process opens the main log when it first needs to write to it, and it keeps the file open in case subsequent entries are required – for example, if a number of different deliveries are being done for the same message. However, remote SMTP deliveries can take a long time, and this means that the file may be kept open long after it is renamed if exicyclog or something similar is being used to rename log files on a regular basis. To ensure that a switch of log files is noticed as soon as possible, Exim calls stat() on the main log’s name before reusing an open file, and if the file does not exist, or its inode has changed, the old file is closed and Exim tries to open the main log from scratch. Thus, an old log file may remain open for quite some time, but no Exim processes should write to it once it has been renamed.
Instead of cycling the main and reject log files by renaming them
periodically, some sites like to use files whose names contain a datestamp,
for example, mainlog-20031225. The datestamp is in the form yyyymmdd.
Exim has support for this way of working. It is enabled by setting the
log_file_path option to a path that includes %D at the point where the
datestamp is required. For example:
log_file_path = /var/spool/exim/log/%slog-%D log_file_path = /var/log/exim-%s-%D.log log_file_path = /var/spool/exim/log/%D-%slog
As before, %s is replaced by “main” or “reject”; the following are examples
of names generated by the above examples:
/var/spool/exim/log/mainlog-20021225 /var/log/exim-reject-20021225.log /var/spool/exim/log/20021225-mainlog
When this form of log file is specified, Exim automatically switches to new files at midnight. It does not make any attempt to compress old logs; you will need to write your own script if you require this. You should not run exicyclog with this form of logging.
The location of the panic log is also determined by log_file_path, but it
is not datestamped, because rotation of the panic log does not make sense.
When generating the name of the panic log, %D is removed from the string.
In addition, if it immediately follows a slash, a following non-alphanumeric
character is removed; otherwise a preceding non-alphanumeric character is
removed. Thus, the three examples above would give these panic log names:
/var/spool/exim/log/paniclog /var/log/exim-panic.log /var/spool/exim/log/paniclog
The use of syslog does not change what Exim logs or the format of its messages, except in one respect. If syslog_timestamp is set false, the timestamps on Exim’s log lines are omitted when these lines are sent to syslog. Apart from that, the same strings are written to syslog as to log files. The syslog “facility” is set to LOG_MAIL, and the program name to “exim” by default, but you can change these by setting the syslog_facility and syslog_processname options, respectively. If Exim was compiled with SYSLOG_LOG_PID set in Local/Makefile (this is the default in src/EDITME), then, on systems that permit it (all except ULTRIX), the LOG_PID flag is set so that the syslog() call adds the pid as well as the time and host name to each line. The three log streams are mapped onto syslog priorities as follows:
Many log lines are written to both mainlog and rejectlog, and some are written to both mainlog and paniclog, so there will be duplicates if these are routed by syslog to the same place. You can suppress this duplication by setting syslog_duplication false.
Exim’s log lines can sometimes be very long, and some of its rejectlog entries contain multiple lines when headers are included. To cope with both these cases, entries written to syslog are split into separate syslog() calls at each internal newline, and also after a maximum of 870 data characters. (This allows for a total syslog line length of 1024, when additions such as timestamps are added.) If you are running a syslog replacement that can handle lines longer than the 1024 characters allowed by RFC 3164, you should set
SYSLOG_LONG_LINES=yes
in Local/Makefile before building Exim. That stops Exim from splitting long lines, but it still splits at internal newlines in reject log entries.
To make it easy to re-assemble split lines later, each component of a split
entry starts with a string of the form [<'n>/<m>] or [<'n'>\<m>]
where <'n> is the component number and <m> is the total number of components
in the entry. The / delimiter is used when the line was split because it was
too long; if it was split because of an internal newline, the \ delimiter is
used. For example, supposing the length limit to be 70 instead of 1000, the
following would be the result of a typical rejection message to mainlog
(LOG_INFO), each line in addition being preceded by the time, host name, and
pid as added by syslog:
$smc\{[1/3] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from [127.0.0.1] (ph10):
[2/3] syntax error in 'From' header when scanning for sender: missing or ma
[3/3] lformed local part in "<>" (envelope sender is <ph10@cam.example>)\}
The same error might cause the following lines to be written to “rejectlog” (LOG_NOTICE):
$smc\{[1/14] 2002-09-16 16:09:43 16RdAL-0006pc-00 rejected from [127.0.0.1] (ph10):
[2/14] syntax error in 'From' header when scanning for sender: missing or ma
[3\14] lformed local part in "<>" (envelope sender is <ph10@cam.example>)
[4\14] Recipients: ph10@some.domain.cam.example
[5\14] P Received: from [127.0.0.1] (ident=ph10)
[6\14] by xxxxx.cam.example with smtp (Exim 4.00)
[7\14] id 16RdAL-0006pc-00
[8\14] for ph10@cam.example; Mon, 16 Sep 2002 16:09:43 +0100
[9\14] F From: <>
[10\14] Subject: this is a test header
[11\14] X-something: this is another header
[12\14] I Message-Id: <E16RdAL-0006pc-00@xxxxx.cam.example>
[13\14] B Bcc:
[14/14] Date: Mon, 16 Sep 2002 16:09:43 +0100\}
Log lines that are neither too long nor contain newlines are written to syslog without modification.
If only syslog is being used, the Exim monitor is unable to provide a log tail display, unless syslog is routing mainlog to a file on the local host and the environment variable EXIMON_LOG_FILE_PATH is set to tell the monitor where it is.
One line is written to the main log for each message received, and for each successful, unsuccessful, and delayed delivery. These lines can readily be picked out by the distinctive two-character flags that immediately follow the timestamp. The flags are:
<= message arrival=> normal message delivery-> additional address in same delivery*> delivery suppressed by -N** delivery failed; address bounced== delivery deferred; temporary problemThe format of the single-line entry in the main log that is written for every message received is shown in the basic example below, which is split over several lines in order to fit it on the page:
2002-10-31 08:57:53 16ZCW1-0005MB-00 <= kryten@dwarf.fict.example H=mailer.fict.example [192.168.123.123] U=exim P=smtp S=5678 id=<incoming message id>
The address immediately following “<=” is the envelope sender address. A bounce message is shown with the sender address “<>”, and if it is locally generated, this is followed by an item of the form
R=<message id>
which is a reference to the message that caused the bounce to be sent.
For messages from other hosts, the H and U fields identify the remote host and record the RFC 1413 identity of the user that sent the message, if one was received. The number given in square brackets is the IP address of the sending host. If there is a single, unparenthesized host name in the H field, as above, it has been verified to correspond to the IP address (see the host_lookup option). If the name is in parentheses, it was the name quoted by the remote host in the SMTP HELO or EHLO command, and has not been verified. If verification yields a different name to that given for HELO or EHLO, the verified name appears first, followed by the HELO or EHLO name in parentheses.
Misconfigured hosts (and mail forgers) sometimes put an IP address, with or without brackets, in the HELO or EHLO command, leading to entries in the log containing text like these examples:
H=(10.21.32.43) [192.168.8.34] H=([10.21.32.43]) [192.168.8.34]
This can be confusing. Only the final address in square brackets can be relied on.
For locally generated messages (that is, messages not received over TCP/IP), the H field is omitted, and the U field contains the login name of the caller of Exim.
For all messages, the P field specifies the protocol used to receive the message. This is the value that is stored in $received_protocol. In the case of incoming SMTP messages, the value indicates whether or not any SMTP extensions (ESMTP), encryption, or authentication were used. If the SMTP session was encrypted, there is an additional X field that records the cipher suite that was used.
The protocol is set to “esmptsa” or “esmtpa” for messages received from hosts that have authenticated themselves using the SMTP AUTH command. The first value is used when the SMTP connection was encrypted (“secure”). In this case there is an additional item A= followed by the name of the authenticator that was used. If an authenticated identification was set up by the authenticator’s server_set_id option, this is logged too, separated by a colon from the authenticator name.
The id field records the existing message id, if present. The size of the received message is given by the S field. When the message is delivered, headers may be removed or added, so that the size of delivered copies of the message may not correspond with this value (and indeed may be different to each other).
The log_selector option can be used to request the logging of additional data when a message is received. See section 48.15 below.
The format of the single-line entry in the main log that is written for every delivery is shown in one of the examples below, for local and remote deliveries, respectively. Each example has been split into two lines in order to fit it on the page:
2002-10-31 08:59:13 16ZCW1-0005MB-00 => marv <marv@hitch.fict.example> R=localuser T=local_delivery 2002-10-31 09:00:10 16ZCW1-0005MB-00 => monk@holistic.fict.example R=dnslookup T=remote_smtp H=holistic.fict.example [192.168.234.234]
For ordinary local deliveries, the original address is given in angle brackets after the final delivery address, which might be a pipe or a file. If intermediate address(es) exist between the original and the final address, the last of these is given in parentheses after the final address. The R and T fields record the router and transport that were used to process the address.
If a shadow transport was run after a successful local delivery, the log line for the successful delivery has an item added on the end, of the form
ST=<shadow transport name>
If the shadow transport did not succeed, the error message is put in parentheses afterwards.
When more than one address is included in a single delivery (for example, two
SMTP RCPT commands in one transaction) the second and subsequent addresses are
flagged with -> instead of =>. When two or more messages are delivered down
a single SMTP connection, an asterisk follows the IP address in the log lines
for the second and subsequent messages.
The generation of a reply message by a filter file gets logged as a “delivery” to the addressee, preceded by “>”.
The log_selector option can be used to request the logging of additional data when a message is delivered. See section 48.15 below.
When a message is discarded as a result of the command “seen finish” being obeyed in a filter file which generates no deliveries, a log entry of the form
2002-12-10 00:50:49 16auJc-0001UB-00 => discarded <low.club@bridge.example> R=userforward
is written, to record why no deliveries are logged. When a message is discarded because it is aliased to “:blackhole:” the log line is like this:
1999-03-02 09:44:33 10HmaX-0005vi-00 => :blackhole: <hole@nowhere.example> R=blackhole_router
When a delivery is deferred, a line of the following form is logged:
2002-12-19 16:20:23 16aiQz-0002Q5-00 == marvin@endrest.example R=dnslookup T=smtp defer (146): Connection refused
In the case of remote deliveries, the error is the one that was given for the last IP address that was tried. Details of individual SMTP failures are also written to the log, so the above line would be preceded by something like
2002-12-19 16:20:23 16aiQz-0002Q5-00 Failed to connect to mail1.endrest.example [192.168.239.239]: Connection refused
When a deferred address is skipped because its retry time has not been reached, a message is written to the log, but this can be suppressed by setting an appropriate value in log_selector.
If a delivery fails because an address cannot be routed, a line of the following form is logged:
1995-12-19 16:20:23 0tRiQz-0002Q5-00 ** jim@trek99.example <jim@trek99.example>: unknown mail domain
If a delivery fails at transport time, the router and transport are shown, and the response from the remote host is included, as in this example:
2002-07-11 07:14:17 17SXDU-000189-00 ** ace400@pb.example R=dnslookup T=remote_smtp: SMTP error from remote mailer after pipelined RCPT TO:<ace400@pb.example>: host pbmail3.py.example [192.168.63.111]: 553 5.3.0 <ace400@pb.example>... Addressee unknown
The word “pipelined” indicates that the SMTP PIPELINING extension was being used. See hosts_avoid_esmtp in the smtp transport for a way of disabling PIPELINING.
The log lines for all forms of delivery failure are flagged with **.
If a delivery does not actually take place because the -N option has been used to suppress it, a normal delivery line is written to the log, except that “=>” is replaced by “*>”.
A line of the form
2002-10-31 09:00:11 16ZCW1-0005MB-00 Completed
is written to the main log when a message is about to be removed from the spool at the end of its processing.
A summary of the field identifiers that are used in log lines is shown in the following table:
A authenticator name (and optional id)C SMTP confirmation on deliveryCV certificate verification statusDN distinguished name from peer certificateDT on => lines: time taken for a deliveryF sender address (on delivery lines)H host name and IP addressI local interface usedid message id for incoming messageP on <= lines: protocol used on => and ** lines: return pathQT on => lines: time spent on queue so far on “Completed” lines: time spent on queueR on <= lines: reference for local bounce on => ** and == lines: router nameS size of messageST shadow transport nameT on <= lines: message subject (topic) on => ** and == lines: transport nameU local user or RFC 1413 identityX TLS cipher suiteVarious other types of log entry are written from time to time. Most should be self-explanatory. Among the more common are:
error ignored There are several circumstances that give rise to this message:
A delivery set up by a router configured with
errors_to = <>
failed. The delivery was discarded.
By setting the log_selector global option, you can disable some of Exim’s default logging, or you can request additional logging. The value of log_selector is made up of names preceded by plus or minus characters. For example:
log_selector = +arguments -retry_defer
The list of optional log items is in the following table, with the default selection marked by asterisks:
*acl_warn_skipped skipped warn statement in ACL address_rewrite address rewriting all_parents all parents in => lines arguments command line arguments*connection_reject connection rejections*delay_delivery immediate delivery delayed deliver_time time taken to perform delivery delivery_size add S=nnn to => lines*dnslist_defer defers of DNS list (aka RBL) lookups*etrn ETRN commands*host_lookup_failed as it says ident_timeout timeout for ident connection incoming_interface incoming interface on <= lines incoming_port incoming port on <= lines*lost_incoming_connection as it says (includes timeouts) outgoing_port add remote port to => lines*queue_run start and end queue runs queue_time time on queue for one recipient queue_time_overall time on queue for whole message received_recipients recipients on <= lines received_sender sender on <= lines*rejected_header header contents on reject log*retry_defer “retry time not reached” return_path_on_delivery put return path on => and *\ lines sender_on_delivery add sender to => lines*size_reject rejection because too big*skip_delivery delivery skipped in a queue run smtp_confirmation SMTP confirmation on => lines smtp_connection SMTP connections smtp_incomplete_transaction incomplete SMTP transactions smtp_protocol_error SMTP protocol errors smtp_syntax_error SMTP syntax errors subject contents of Subject: on <= lines tls_certificate_verified certificate verification status*tls_cipher TLS cipher suite on <= and => lines tls_peerdn TLS peer DN on <= and => lines unknown_in_list DNS lookup failed in list match all all of the aboveMore details on each of these items follows:
DT=1s.
=>) lines, for example,
QT=3m45s. The clock starts when Exim starts to receive the message, so it
includes reception time as well as the delivery time for the current address.
This means that it may be longer than the difference between the arrival and
delivery log line times, because the arrival log line is not written until the
message has been successfully received.
QT=3m45s. The clock starts when Exim starts to receive the
message, so it includes reception time as well as the total delivery time.
:blackhole:.
smtp_connection: A log line is written whenever an SMTP connection is established or closed, unless the connection is from a host that matches hosts_connection_nolog. (In contrast, lost_incoming_connection applies only when the closure is unexpected.) This applies to connections from local processes that use -bs as well as to TCP/IP connections. If a connection is dropped in the middle of a message, a log line is always written, whether or not this selector is set, but otherwise nothing is written at the start and end of connections unless this selector is enabled.
For TCP/IP connections to an Exim daemon, the current number of connections is included in the log message for each new connection, but note that the count is reset if the daemon is restarted. Also, because connections are closed (and the closure is logged) in subprocesses, the count may not include connections that have been closed but whose termination the daemon has not yet noticed. Thus, while it is possible to match up the opening and closing of connections in the log, the value of the logged counts may not be entirely accurate.
CV=yes if the peer’s certificate was
verified, and CV=no if not.
In addition to the general log files, Exim writes a log file for each message that it handles. The names of these per-message logs are the message ids, and
they are kept in the msglog sub-directory of the spool directory. Each message log contains copies of the log lines that apply to the message. This makes it easier to inspect the status of an individual message without having to search the main log. A message log is deleted when processing of the message is complete,
unless preserve_message_logs is set, but this should be used only with great care because they can fill up your disk very quickly.
On a heavily loaded system, it may be desirable to disable the use of per-message logs, in order to reduce disk I/O. This can be done by setting the message_logs option false.