Access Control Lists (ACLs) are defined in a separate section of the run time configuration file, headed by “begin acl”. Each ACL definition starts with a name, terminated by a colon. Here is a complete ACL section which contains just one very small ACL:
begin acl small_acl: accept hosts = one.host.only
You can have as many lists as you like in the ACL section, and the order in which they appear does not matter. The lists are self-terminating.
The majority of ACLs are used to control Exim's behaviour when it receives certain SMTP commands. This applies both to incoming TCP/IP connections, and when a local process submits a message over a pipe (using the -bs option). The most common use is for controlling which recipients are accepted in incoming messages. In addition, you can also define an ACL that is used to check local non-SMTP messages. The default configuration file contains an example of a realistic ACL for checking RCPT commands. This is discussed in chapter 7.
The -bh command line option provides a way of testing your ACL configuration locally by running a fake SMTP session with which you interact. The host relay-test.mail-abuse.org provides a service for checking your relaying configuration (see section 38.27 for more details).
In order to cause an ACL to be used, you have to name it in one of the relevant options in the main part of the configuration. These options are:
| acl_not_smtp | ACL for non-SMTP messages |
| acl_smtp_auth | ACL for AUTH |
| acl_smtp_connect | ACL for start of SMTP connection |
| acl_smtp_data | ACL after DATA |
| acl_smtp_etrn | ACL for ETRN |
| acl_smtp_expn | ACL for EXPN |
| acl_smtp_helo | ACL for HELO or EHLO |
| acl_smtp_mail | ACL for MAIL |
| acl_smtp_mailauth | ACL for the AUTH parameter of MAIL |
| acl_smtp_rcpt | ACL for RCPT |
| acl_smtp_starttls | ACL for STARTTLS |
| acl_smtp_vrfy | ACL for VRFY |
For example, if you set
acl_smtp_rcpt = small_acl
the little ACL defined above is used whenever Exim receives a RCPT command in an SMTP dialogue. The majority of policy tests on incoming messages can be done when RCPT commands arrive. A rejection of RCPT should cause the sending MTA to give up on the recipient address contained in the RCPT command, whereas rejection at other times may cause the client MTA to keep on trying to deliver the message. It is therefore recommended that you do as much testing as possible at RCPT time.
However, you cannot test the contents of the message, for example, to verify addresses in the headers, at RCPT time. Such tests have to appear in the ACL that is run after the message has been received, before the final response to the DATA command is sent. This is the ACL specified by acl_smtp_data. At this time, it is no longer possible to reject individual recipients. An error response should reject the entire message. Unfortunately, it is known that some MTAs do not treat hard (5xx) errors correctly at this point – they keep the message on their queues and try again later, but that is their problem, though it does waste some of your resources.
The ACL test specified by acl_smtp_connect happens after the test specified by host_reject_connection (which is now an anomaly) and any TCP Wrappers testing (if configured).
The non-SMTP ACL applies to all non-interactive incoming messages, that is, it applies to batch SMTP as well as to non-SMTP messages. (Batch SMTP is not really SMTP.) This ACL is run just before the local_scan() function. Any kind of rejection is treated as permanent, because there is no way of sending a temporary error for these kinds of message. Many of the ACL conditions (for example, host tests, and tests on the state of the SMTP connection such as encryption and authentication) are not relevant and are forbidden in this ACL.
The result of running an ACL is either “accept” or “deny”, or, if some test cannot be completed (for example, if a database is down), “defer”. These results cause 2xx, 5xx, and 4xx return codes, respectively, to be used in the SMTP dialogue. A fourth return, “error”, occurs when there is an error such as invalid syntax in the ACL. This also causes a 4xx return code.
The ACLs that are relevant to message reception may also return “discard”. This has the effect of “accept”, but causes either the entire message or an individual recipient address to be discarded. In other words, it is a blackholing facility. Use it with great care.
If the ACL for MAIL returns “discard”, all recipients are discarded, and no ACL is run for subsequent RCPT commands. The effect of “discard” in a RCPT ACL is to discard just the one address. If there are no recipients left when the message's data is received, the DATA ACL is not run. A “discard” return from the DATA or the non-SMTP ACL discards all the remaining recipients.
The local_scan() function is always run, even if there are no remaining recipients; it may create new recipients.
The default actions when any of the acl_xxx options are unset are not all the same. Note: These defaults apply only when the relevant ACL is not defined at all. For any defined ACL, the default action if control reaches the end of the ACL statements is “deny”.
For acl_not_smtp, acl_smtp_auth, acl_smtp_connect, acl_smtp_data, acl_smtp_helo, acl_smtp_mail, acl_smtp_mailauth, and acl_smtp_starttls, the action when the ACL is not defined is “accept”.
For the others (acl_smtp_etrn, acl_smtp_expn, acl_smtp_rcpt, and acl_smtp_vrfy), the action when the ACL is not defined is “deny”. This means that acl_smtp_rcpt must be defined in order to receive any messages over an SMTP connection. For an example, see the ACL in the default configuration file.
When an ACL for MAIL, RCPT, or DATA is being run, the variables that contain information about the host and the message's sender (for example, $sender_host_address and $sender_address) are set, and can be used in ACL statements. In the case of RCPT (but not MAIL or DATA), $domain and $local_part are set from the argument address.
When an ACL for the AUTH parameter of MAIL is being run, the variables that contain information about the host are set, but $sender_address is not yet set.
The $message_size variable is set to the value of the SIZE parameter on the MAIL command at MAIL and RCPT time, or -1 if that parameter was not given. Its value is updated to the true message size by the time the ACL after DATA is run.
The $rcpt_count variable increases by one for each RCPT command received. The $recipients_count variable increases by one each time a RCPT command is accepted, so while an ACL for RCPT is being processed, it contains the number of previously accepted recipients. At DATA time, $rcpt_count contains the total number of RCPT commands, and $recipients_count contains the total number of accepted recipients.
When an ACL for AUTH, ETRN, EXPN, STARTTLS, or VRFY is being run, the remainder of the SMTP command line is placed in $smtp_command_argument. This can be tested using a condition condition. For example, here is an ACL for use with AUTH, which insists that either the session is encrypted, or the CRAM-MD5 authentication method is used. In other words, it does not permit authentication methods that use cleartext passwords on unencrypted connections.
acl_check_auth:
accept encrypted = *
accept condition = ${if eq{${uc:$smtp_command_argument}}\
{CRAM-MD5}{yes}{no}}
deny message = TLS encryption or CRAM-MD5 required
(Another way of applying this restriction is to arrange for the authenticators that use cleartext passwords not to be advertised when the connection is not encrypted. You can use the generic server_advertise_condition authenticator option to do this.)
The value of an acl_smtp_xxx option is expanded before use, so you can use different ACLs in different circumstances, and in fact the resulting string does not have to be the name of a configured list. Having expanded the string, Exim searches for an ACL as follows:
If the string begins with a slash, Exim attempts to open the file and read its contents as an ACL. The lines are processed in the same way as lines in the Exim configuration file. In particular, continuation lines are supported, blank lines are ignored, as are lines whose first non-whitespace character is “#”. If the file does not exist or cannot be read, an error occurs (typically causing a temporary failure of whatever caused the ACL to be run). For example:
acl_smtp_data = /etc/acls/\
${lookup{$sender_host_address}lsearch\
{/etc/acllist}{$value}{default}}
This looks up an ACL file to use on the basis of the host's IP address, falling back to a default if the lookup fails. If an ACL is successfully read from a file, it is retained in memory for the duration of the Exim process, so that it can be re-used without having to re-read the file.
If the string does not start with a slash, and does not contain any spaces, Exim searches the ACL section of the configuration for a list whose name matches the string.
If no named ACL is found, or if the string contains spaces, Exim parses the string as an inline ACL. This can save typing in cases where you just want to have something like
acl_smtp_vrfy = accept
in order to allow free use of the VRFY command. Such a string may contain newlines; it is processed in the same way as an ACL that is read from a file.
An individual ACL consists of a number of statements. Each statement starts with a verb, optionally followed by a number of conditions and other modifiers. If all the conditions are met, the verb is obeyed. The same condition may be used (with different arguments) more than once in the same statement. This provides a means of specifying an “and” conjunction between conditions. For example:
deny dnslists = list1.example dnslists = list2.example
If there are no conditions, the verb is always obeyed. What happens if any of the conditions are not met depends on the verb (and in one case, on a special modifier). Not all the conditions make sense at every testing point. For example, you cannot test a sender address in the ACL that is run for a VRFY command.
The verbs are as follows:
accept: If all the conditions are met, the ACL returns “accept”. If any of the conditions are not met, what happens depends on whether endpass appears among the conditions (for syntax see below). If the failing condition precedes endpass, control is passed to the next ACL statement; if it follows endpass, the ACL returns “deny”. Consider this statement, used to check a RCPT command:
accept domains = +local_domains endpass verify = recipient
If the recipient domain does not match the domains condition, control passes to the next statement. If it does match, the recipient is verified, and the command is accepted if verification succeeds. However, if verification fails, the ACL yields “deny”, because the failing condition is after endpass.
defer: If all the conditions are met, the ACL returns “defer” which, in an SMTP session, causes a 4xx response to be given. For a non-SMTP ACL, defer is the same as deny, because there is no way of sending a temporary error. For a RCPT command, defer is much the same as using a redirect router and :defer: while verifying, but the defer verb can be used in any ACL, and even for a recipient it might be a simpler approach.
deny: If all the conditions are met, the ACL returns “deny”. If any of the conditions are not met, control is passed to the next ACL statement. For example,
deny dnslists = blackholes.mail-abuse.org
rejects commands from hosts that are on a DNS black list.
discard: This verb behaves like accept, except that it returns “discard” from the ACL instead of “accept”. It is permitted only on ACLs that are concerned with receiving messages, and it causes recipients to be discarded. If the log_message modifier is set when discard operates, its contents are added to the line that is automatically written to the log.
If discard is used in an ACL for RCPT, just the one recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the message's recipients are discarded. Recipients that are discarded before DATA do not appear in the log line when the log_recipients log selector is set.
drop: This verb behaves like deny, except that an SMTP connection is forcibly closed after the 5xx error message has been sent. For example:
drop message = I don't take more than 20 RCPTs
condition = ${if > {$rcpt_count}{20}{yes}{no}}
There is no difference between deny and drop for the connect-time ACL. The connection is always dropped after sending a 550 response.
require: If all the conditions are met, control is passed to the next ACL statement. If any of the conditions are not met, the ACL returns “deny”. For example, when checking a RCPT command,
require verify = sender
passes control to subsequent statements only if the message's sender can be verified. Otherwise, it rejects the command.
warn: If all the conditions are met, a header line is added to an incoming message and/or a line is written to Exim's main log. In all cases, control passes to the next ACL statement. The text of the added header line and the log line are specified by modifiers; if they are not present, a warn verb just checks its conditions and obeys any “immediate” modifiers such as set and logwrite.
If any condition on a warn statement cannot be completed (that is, there is some sort of defer), no header is added and the configured log line is not written. No further conditions or modifiers in the warn statement are processed. The incident is logged, but the ACL continues to be processed, from the next statement onwards.
When testing an incoming message, the message modifier can be used on a warn statement to add an extra header line, as in this example:
warn message = X-blacklisted-at: $dnslist_domain dnslists = blackholes.mail-abuse.org : \ dialup.mail-abuse.org
If an identical header line is requested several times (provoked, for example, by multiple RCPT commands), only one copy is actually added to the message. If the text of the message modifier is not a valid header line, X-ACL-Warn: is added to the front of it.
Header lines that are added by an ACL at MAIL or RCPT time are not visible in string expansions in the ACL for subsequent RCPT commands. However they are visible in string expansions in the ACL that is run after DATA. If you want to preserve data between MAIL and RCPT ACLs, you can use ACL variables, as described in the next section. If a message is rejected after DATA, all added header lines are included in the entry that is written to the reject log.
If a message modifier is present on a warn verb in an ACL that is not testing an incoming message, it is ignored, and the incident is logged.
A warn statement may use the log_message modifier to cause a line to be written to the main log when the statement's conditions are true. Just as for message, if an identical log line is requested several times in the same message, only one copy is actually written to the log. If you want to force duplicates to be written, use the logwrite modifier instead.
When one of the warn conditions is an address verification that fails, the text of the verification failure message is in $acl_verify_message. If you want this logged, you must set it up explicitly. For example:
warn !verify = sender log_message = sender verify failed: $acl_verify_message
At the end of each ACL there is an implicit unconditional deny.
As you can see from the examples above, the conditions and modifiers are written one to a line, with the first one on the same line as the verb, and subsequent ones on following lines. If you have a very long condition, you can continue it onto several physical lines by the usual \ continuation mechanism. It is conventional to align the conditions vertically.
There are some special variables that can be set during ACL processing. They can be used to pass information between different ACLs, different invocations of the same ACL in the same SMTP connection, and between ACLs and the routers, transports, and filters that are used to deliver a message. There are two sets of these variables:
The values of $acl_c0 to $acl_c9 persist throughout an SMTP connection. They are never reset. Thus, a value that is set while receiving one message is still available when receiving the next message on the same SMTP connection.
The values of $acl_m0 to $acl_m9 persist only while a message is being received. They are reset afterwards. They are also reset by MAIL, RSET, EHLO, HELO, and after starting up a TLS session.
When a message is accepted, the current values of all the ACL variables are preserved with the message and are subsequently made available at delivery time.
The ACL variables are set by modifier called set. For example:
accept hosts = whatever set acl_m4 = some value
Note that the leading dollar sign is not used when naming a variable that is to be set. If you want to set a variable without taking any action, you can use a warn verb without any other modifiers.
An exclamation mark preceding a condition negates its result. For example,
deny domains = *.dom.example !verify = recipient
causes the ACL to return “deny” if the recipient domain ends in dom.example, but the recipient address cannot be verified.
The arguments of conditions and modifiers are expanded. A forced failure of an expansion causes a condition to be ignored, that is, it behaves as if the condition is true. Consider these two statements:
accept senders = ${lookup{$host_name}lsearch\
{/some/file}{$value}fail}
accept senders = ${lookup{$host_name}lsearch\
{/some/file}{$value}{}}
Each attempts to look up a list of acceptable senders. If the lookup succeeds, the returned list is searched, but if the lookup fails the behaviour is different in the two cases. The fail in the first statement causes the condition to be ignored, leaving no further conditions. The accept verb therefore succeeds. The second statement, however, generates an empty list when the lookup fails. No sender can match an empty list, so the condition fails, and therefore the accept also fails.
ACL modifiers appear mixed in with conditions in ACL statements. Some of them specify actions that are taken as the conditions for a statement are checked; others specify text for messages that are used when access is denied or a warning is generated.
The positioning of the modifiers in an ACL statement important, because the processing of a verb ceases as soon as its outcome is known. Only those modifiers that have already been encountered will take effect. For the accept and require statements, this means that processing stops as soon as a false condition is met. For example, consider this use of the message modifier:
require message = Can't verify sender verify = sender message = Can't verify recipient verify = recipient message = This message cannot be used
If sender verification fails, Exim knows that the result of the statement is “deny”, so it goes no further. The first message modifier has been seen, so its text is used as the error message. If sender verification succeeds, but recipient verification fails, the second message is used. If recipient verification succeeds, the third message becomes “current”, but is never used because there are no more conditions to cause failure.
For the deny verb, on the other hand, it is always the last message modifier that is used, because all the conditions must be true for rejection to happen. Specifying more than one message modifier does not make sense, and the message can even be specified after all the conditions. For example:
deny hosts = ... !senders = *@my.domain.example message = Invalid sender from client host
The “deny” result does
Exim's command line takes the standard Unix form of a sequence of options, each starting with a hyphen character, followed by a number of arguments. The options are compatible with the main options of Sendmail, and there are also some additional options, some of which are compatible with Smail 3. Certain combinations of options do not make sense, and provoke an error if used. The form of the arguments depends on which options are set.
If Exim is called under the name mailq, it behaves as if the option -bp were present before any other options. The -bp option requests a listing of the contents of the mail queue on the standard output. This feature is for compatibility with some systems that contain a command of that name in one of the standard libraries, symbolically linked to /usr/sbin/sendmail or /usr/lib/sendmail.
If Exim is called under the name rsmtp it behaves as if the option -bS were present before any other options, for compatibility with Smail. The -bS option is used for reading in a number of messages in batched SMTP format.
If Exim is called under the name rmail it behaves as if the -i and -oee options were present before any other options, for compatibility with Smail. The name rmail is used as an interface by some UUCP systems.
If Exim is called under the name runq it behaves as if the option -q were present before any other options, for compatibility with Smail. The -q option causes a single queue runner process to be started.
If Exim is called under the name newaliases it behaves as if the option -bi were present before any other options, for compatibility with Sendmail. This option is used for rebuilding Sendmail's alias file. Exim does not have the concept of a single alias file, but can be configured to run a given command if called with the -bi option.
Some Exim options are available only to trusted users and others are available only to admin users. In the description below, the phrases “Exim user” and “Exim group” mean the user and group defined by EXIM_USER and EXIM_GROUP in Local/Makefile or set by the exim_user and exim_group options. These do not necessarily have to use the name “exim”.
The trusted users are root, the Exim user, any user listed in the trusted_users configuration option, and any user whose current group or any supplementary group is one of those listed in the trusted_groups configuration option. Note that the Exim group is not automatically trusted.
Trusted users are always permitted to use the -f option or a leading “From ” line to specify the envelope sender of a message that is passed to Exim through the local interface (see the -bm and -f options below). See the untrusted_set_sender option for a way of permitting non-trusted users to set envelope senders. For a trusted user, there is never any check on the contents of the From: header line, and a Sender: line is never added. Furthermore, any existing Sender: line in incoming local (non-TCP/IP) messages is not removed.
Trusted users may also specify a host name, host address, interface address, protocol name, ident value, and authentication data when submitting a message locally. Thus, they are able to insert messages into Exim's queue locally that have the characteristics of messages received from a remote host. Untrusted users may in some circumstances use -f, but can never set the other values that are available to trusted users.
The admin users are root, the Exim user, and any user that is a member of the Exim group or of any group listed in the admin_groups configuration option. The current group does not have to be one of these groups.
Admin users are permitted to list the queue, and to carry out certain operations on messages, for example, to force delivery failures. It is also necessary to be an admin user in order to see the full information provided by the Exim monitor, and full debugging output.
By default, the use of the -M, -q, -R, and -S options to cause Exim to attempt delivery of messages on its queue is restricted to admin users. However, this restriction can be relaxed by setting the prod_requires_admin option false (that is, specifying no_prod_requires_admin).
Similarly, the use of the -bp option to list all the messages in the queue is restricted to admin users unless queue_list_requires_admin is set false.
Warning: If you configure your system so that admin users are able to edit Exim's configuration file, you are giving those users an easy way of getting root. There is further discussion of this issue at the start of chapter 6.
The command options are described in alphabetical order below.
This is a pseudo-option whose only purpose is to terminate the options and therefore to cause subsequent command line items to be treated as arguments rather than options, even if they begin with hyphens.
This option causes Exim to output a few sentences stating what it is. The same output is generated if the Exim binary is called with no options and no arguments.
This is a Sendmail option for selecting 7 or 8 bit processing. Exim is 8-bit clean; it ignores this option.
This option runs Exim as a daemon, awaiting incoming SMTP connections. Usually the -bd option is combined with the -q<time> option, to specify that the daemon should also initiate periodic queue runs.
The -bd option can be used only by an admin user. If either of the -d (debugging) or -v (verifying) options are set, the daemon does not disconnect from the controlling terminal. When running this way, it can be stopped by pressing ctrl-C.
By default, Exim listens for incoming connections to the standard SMTP port on all the host's running interfaces. However, it is possible to listen on other ports, on multiple ports, and only on specific interfaces. Chapter 13 contains a description of the options that control this.
When a listening daemon is started without the use of -oX (that is, without overriding the normal configuration), it writes its process id to a file called exim-daemon.pid in Exim's spool directory. This location can be overridden by setting PID_FILE_PATH in Local/Makefile. The file is written while Exim is still running as root.
When -oX is used on the command line to start a listening daemon, the process id is not written to the normal pid file path. However, -oP can be used to specify a path on the command line if a pid file is required.
The SIGHUP signal can be used to cause the daemon to re-exec itself. This should be done whenever Exim's configuration file, or any file that is incorporated into it by means of the .include facility, is changed, and also whenever a new version of Exim is installed. It is not necessary to do this when other files that are referenced from the configuration (for example, alias files) are changed, because these are reread each time they are used.
This option has the same effect as -bd except that it never disconnects from the controlling terminal, even when no debugging is specified.
Run Exim in expansion testing mode. Exim discards its root privilege, to prevent ordinary users from using this mode to read otherwise inaccessible files. If no arguments are given, Exim runs interactively, prompting for lines of data. Long expressions can be split over several lines by using backslash continuations. As in Exim's run time configuration, whitespace at the start of continuation lines is ignored.
Each argument or data line is passed through the string expansion mechanism, and the result is output. Variable values from the configuration file (for example, $qualify_domain) are available, but no message-specific values (such as $domain) are set, because no message is being processed.
This option is the same as -bf except that it assumes that the filter being tested is a system filter. The additional commands that are available only in system filters are recognized.
This option runs Exim in filter testing mode; the file is the filter file to be tested, and a test message must be supplied on the standard input. If there are no message-dependent tests in the filter, an empty file can be supplied. If a system filter file is being tested, -bF should be used instead of -bf. If the test file does not begin with one of the special lines
# Exim filter # Sieve filter
it is taken to be a normal .forward file, and is tested for validity under that interpretation. See sections 22.4 to 22.6 for a description of the possible contents of non-filter redirection lists.
The result of an Exim command that uses -bf, provided no errors are detected, is a list of the actions that Exim would try to take if presented with the message for real. More details of filter testing are given in the separate document entitled Exim's interfaces to mail filtering.
When testing a filter file, the envelope sender can be set by the -f option, or by a “From ” line at the start of the test message. Various parameters that would normally be taken from the envelope recipient address of the message can be set by means of additional command line options. These are:
| -bfd | <domain> | default is the qualify domain |
| -bfl | <local_part> | default is the logged in user |
| -bfp | <local_part_prefix> | default is null |
| -bfs | <local_part_suffix> | default is null |
The local part should always be set to the incoming address with any prefix or suffix stripped, because that is how it appears to the filter when a message is actually being delivered.
This option runs a fake SMTP session as if from the given IP address, using the standard input and output. The IP address may include a port number at the end, after a full stop. For example:
exim -bh 10.9.8.7.1234 exim -bh fe80::a00:20ff:fe86:a061.5678
Comments as to what is going on are written to the standard error file. These include lines beginning with “LOG” for anything that would have been logged. This facility is provided for testing configuration options for incoming messages, to make sure they implement the required policy. For example, you can test your relay controls using -bh.
Warning 1: You cannot test features of the configuration that rely on ident (RFC 1413) callouts. These cannot be done when testing using -bh because there is no incoming SMTP connection.
Warning 2: Address verification callouts (see section 38.21) are also skipped when testing using -bh. If you want these callouts to occur, use -bhc instead.
Messages supplied during the testing session are discarded, and nothing is written to any of the real log files. There may be pauses when DNS (and other) lookups are taking place, and of course these may time out. The -oMi option can be used to specify a specific IP interface and port if this is important.
The exim_checkaccess utility is a “packaged” version of -bh whose output just states whether a given recipient address from a given host is acceptable or not. See section 46.8.
This option operates in the same way as -bh, except that address verification callouts are performed if required. This includes consulting and updating the callout cache database.
Sendmail interprets the -bi option as a request to rebuild its alias file. Exim does not have the concept of a single alias file, and so it cannot mimic this behaviour. However, calls to /usr/lib/sendmail with the -bi option tend to appear in various scripts such as NIS make files, so the option must be recognized.
If -bi is encountered, the command specified by the bi_command configuration option is run, under the uid and gid of the caller of Exim. If the -oA option is used, its value is passed to the command as an argument. The command set by bi_command may not contain arguments. The command can use the exim_dbmbuild utility, or some other means, to rebuild alias files if this is required. If the bi_command option is not set, calling Exim with -bi is a no-op.
This option runs an Exim receiving process that accepts an incoming, locally-generated message on the current input. The recipients are given as the command arguments (except when -t is also present – see below). Each argument can be a comma-separated list of RFC 2822 addresses. This is the default option for selecting the overall action of an Exim call; it is assumed if no other conflicting option is present.
If any addresses in the message are unqualified (have no domain), they are qualified by the values of the qualify_domain or qualify_recipient options, as appropriate. The -bnq option (see below) provides a way of suppressing this for special cases.
Policy checks on the contents of local messages can be enforced by means of the non-SMTP ACL. See chapter 38 for details. The return code is zero if the message is successfully accepted. Otherwise, the action is controlled by the -oex option setting – see below.
The format of the message must be as defined in RFC 2822, except that, for compatibility with Sendmail and Smail, a line in one of the forms
From sender Fri Jan 5 12:55 GMT 1997
From sender Fri, 5 Jan 97 12:55:01
(with the weekday optional, and possibly with additional text after the date) is permitted to appear at the start of the message. There appears to be no authoritative specification of the format of this line. Exim recognizes it by matching against the regular expression defined by the uucp_from_pattern option, which can be changed if necessary. The specified sender is treated as if it were given as the argument to the -f option, but if a -f option is also present, its argument is used in preference to the address taken from the message. The caller of Exim must be a trusted user for the sender of a message to be set in this way.
By default, Exim automatically qualifies unqualified addresses (those without domains) that appear in messages that are submitted locally (that is, not over TCP/IP). This qualification applies both to addresses in envelopes, and addresses in header lines. Sender addresses are qualified using qualify_domain, and recipient addresses using qualify_recipient (which defaults to the value of qualify_domain).
Sometimes, qualification is not wanted. For example, if -bS (batch SMTP) is being used to re-submit messages that originally came from remote hosts after content scanning, you probably do not want to qualify unqualified addresses in header lines. (Such lines will be present only if you have not enabled a header syntax check in the appropriate ACL.)
The -bnq option suppresses all qualification of unqualified addresses in messages that originate on the local host. When this is used, unqualified addresses in the envelope provoke errors (causing message rejection) and unqualified addresses in header lines are left alone.
If this option is given with no arguments, it causes the values of all Exim's main configuration options to be written to the standard output. The values of one or more specific options can be requested by giving their names as arguments, for example:
exim -bP qualify_domain hold_domains
However, any option setting that is preceded by the word “hide” in the configuration file is not shown in full, except to an admin user. For other users, the output is as in this example:
mysql_servers = <value not displayable>
If configure_file is given as an argument, the name of the run time configuration file is output. If a list of configuration files was supplied, the value that is output here is the name of the file that was actually used.
If log_file_path or pid_file_path are given, the names of the directories where log files and daemon pid files are written are output, respectively. If these values are unset, log files are written in a sub-directory of the spool directory called log, and the pid file is written directly into the spool directory.
If -bP is followed by a name preceded by +, for example,
exim -bP +local_domains
it searches for a matching named list of any type (domain, host, address, or local part) and outputs what it finds.
If one of the words router, transport, or authenticator is given, followed by the name of an appropriate driver instance, the option settings for that driver are output. For example:
exim -bP transport local_delivery
The generic driver options are output first, followed by the driver's private options. A list of the names of drivers of a particular type can be obtained by using one of the words router_list, transport_list, or authenticator_list, and a complete list of all drivers with their option settings can be obtained by using routers, transports, or authenticators.
This option requests a listing of the contents of the mail queue on the standard output. If the -bp option is followed by a list of message ids, just those messages are listed. By default, this option can be used only by an admin user. However, the queue_list_requires_admin option can be set false to allow any user to see the queue.
Each message on the queue is displayed as in the following example:
25m 2.9K 0t5C6f-0000c8-00 <alice@wonderland.fict.example>
red.king@looking-glass.fict.example
<other addresses>
The first line contains the length of time the message has been on the queue (in this case 25 minutes), the size of the message (2.9K), the unique local identifier for the message, and the message sender, as contained in the envelope. For bounce messages, the sender address is empty, and appears as “<>”. If the message was submitted locally by an untrusted user who overrode the default sender address, the user's login name is shown in parentheses before the sender address. If the message is frozen (attempts to deliver it are suspended) then the text “*** frozen ***” is displayed at the end of this line.
The recipients of the message (taken from the envelope, not the headers) are displayed on subsequent lines. Those addresses to which the message has already been delivered are marked with the letter D. If an original address gets expanded into several addresses via an alias or forward file, the original is displayed with a D only when deliveries for all of its child addresses are complete.
This option operates like -bp, but in addition it shows delivered addresses that were generated from the original top level address(es) in each message by alias or forwarding operations. These addresses are flagged with “+D” instead of just “D”.
This option counts the number of messages on the queue, and writes the total to the standard output. It is restricted to admin users, unless queue_list_requires_admin is set false.
This option operates like -bp, but the output is not sorted into chronological order of message arrival. This can speed it up when there are lots of messages on the queue, and is particularly useful if the output is going to be post-processed in a way that doesn't need the sorting.
This option is a combination of -bpr and -bpa.
This option is a combination of -bpr and -bpu.
This option operates like -bp but shows only undelivered top-level addresses for each message displayed. Addresses generated by aliasing or forwarding are not shown, unless the message was deferred after processing by a router with the one_time option set.
This option is for testing retry rules, and it must be followed by up to three arguments. It causes Exim to look for a retry