Provided by: courier-mta_0.66.1-1ubuntu4_i386 bug

NAME

       courier - The Courier mail server

SYNOPSIS

       courier {start | stop | restart | flush | flush qid  |
               clear user@domain  | clear all  | show all }

DESCRIPTION

       The Courier mail server is a modular multi-protocol E-mail transport
       agent. The courier command is an administrative command, and most of
       its options are only available to the superuser.

       "courier start" starts the server by running
       /usr/lib/courier/courierctl.start in the background. "courier stop"
       immediately stops all the Courier mail server processes and aborts all
       current mail deliveries. "courier restart" restarts the Courier mail
       server server. A restart is often needed for certain configuration
       changes to take effect. "courier restart" waits for all current
       deliveries to complete before restarting. This is the "nice" way to
       restart the mail server. "courier flush" takes all undelivered messages
       in the queue and attempts to deliver them immediately, instead of
       waiting until their next scheduled attempted delivery time. "courier
       flush" can be optionally followed by a message queue ID in order to
       schedule an immediate delivery attempt for only a single message.
       Message queue IDs are displayed by the mailq(1)[1] command.

       Please note that courier start runs the main Courier mail server
       scheduling engine only. It does not start any other daemons that you
       may have, such as the ESMTP or the IMAP daemon.

       "courier show all" lists all E-mail addresses currently blacklisted for
       backscatter. "courier clear user@domain" manually clears <user@domain>
       from the backscatter blacklist. "courier clear all" removes all
       addresses from the backscatter blacklist. When the Courier mail server
       encounters a delivery failure to an E-mail address the Courier mail
       server may stop accepting any more messages to the same address in
       order to minimize generation of so-called "backscatter bounces". This
       does not occur in all cases, see "Backscatter suppresion" in the
       Courier mail server's installation instructions for more information.

       The Courier mail server will resume accepting messages to the
       blacklisted address if the delivery attempt originally encountered a
       temporary failure, and a subsequent retry succesfully delivered the
       message, or if more than two hours elapsed since the delivery failure.
       Use the "clear" command to manually clear the E-mail address from the
       backscatter blacklist. This may be useful if the undeliverable message
       is manually removed from the Courier mail server's mail queue, using
       the "cancel" command. Even if the message is cancelled, the Courier
       mail server will continue to refuse accepting mail for this address for
       up to two hours. The "clear" command can be use to reenable mail
       acceptance before then.

   CONFIGURATION FILES
       The Courier mail server uses several configuration files which are
       located in /etc/courier. These configuration files are plain text files
       that can be modified with any text editor. In certain instances a
       subdirectory is used, and all plain text files in the subdirectory are
       concatenated and are considered to be a single, consolidated,
       configuration file. Unless otherwise specified, you must run courier
       restart for any changes to these files to take effect.

       aliasfilteracct
           This file contains one line, containing the home directory of the
           account that's used for filtering mail addressed to local alias
           lists.

           When mail filtering is enabled, local recipients have the ability
           to define mail filters which can selectively reject unwanted mail.
           /etc/courier/aliases may define local mail aliases that contain one
           or more recipients. If it is desired to use local mail filtering
           for mail addressed to an alias address, designate a local account
           that will be used to specify filtering instructions, and put its
           home directory into this control file. The filtering argument will
           be "alias-address" where address is the name of the alias. See
           localmailfilter(7)[2] for more information.

           Due to technical limitations, content filtering is not available
           for multiple-recipient aliases.

           Changes to this file take effect immediately.

       authdaemonrc
           This file configures the authdaemond authentication proxy. See
           authlib(7)[3] for more information.

       authldaprc
           This file configures LDAP authentication. See authlib(7)[3] for
           more information.

       authmysqlrc
           This file configures MySQL authentication. See authlib(7)[3] for
           more information.

       autoresponsesquota
           This file sets the systemwide quota on autoreplies, if autoreplies
           and mail filtering are enabled. Note that this can only really be
           effective if there is no login access to the mail account, since
           this autoreply quota can be trivially overriden.

           The autoresponsesquota file contains one line: "Cnnn" or "Snnn" (or
           both strings, on the same line).  Cnnn: allow up to #nnn
           autoreplies to be created.  Snnn: allow up to #nnn bytes as the
           total size of all autoreplies, combined. If both Cnnn and Snnn are
           specified, both quotas apply. If this file does not exist, there is
           no limit on autoreplies. This quota setting applies systemwide. To
           override the quota setting for a particular Maildir, create the
           autoresponsesquota file in that Maildir (which takes precedence).

       backuprelay
           This file contains one line, containing a name of a machine where
           mail will be rerouted if it cannot be immediately delivered. Spaces
           are not allowed in this file.

           Mail gets rerouted if it cannot be delivered after the time
           interval specified by the warntime configuration file. When
           backuprelay is provided a delayed delivery status notification will
           NOT be generated. The message will be rerouted even if the
           recipient's delivery status notification setting does not include a
           delayed notification request.

           This feature is intended for use by relays that handle large
           quantities of mail, where you don't want to accumulate a large mail
           queue for unreachable mail servers. Please note that ALL
           undeliverable mail will be rerouted in this fashion. Even if the
           recipient of a message is a local recipient - and the recipient's
           mail filter is rejecting the message with a temporary error code -
           the message will still be rerouted if it's undeliverable after the
           specified amount of time.

           Although currently SMTP is the only meaningful application for this
           feature, the Courier mail server is a protocol-independent mail
           server, and the backup relay function can be extended to other
           protocols, as they become available.

           Multiple backup relays can be used by simply assigning multiple IP
           addresses to the same machine name. Note that the Courier mail
           server checks for both MX and A records for the machine specified
           in this configuration file.

           It's important to note that when this setting is specified, warning
           messages get turned off for all messages, including messages
           addressed to local recipients. If a temporary delivery error
           prevents a message from being delivered to a local mailbox, it
           remains in the queue until the temporary error condition gets
           cleared. Normally, if the message remains in the queue beyond the
           warning interval, the warning message gets generated. When this
           setting is specified, the warning message gets replaced with a
           forward to the backup relay, but this occurs only for messages that
           are delivered via SMTP.

       batchsize
           This file contains one line, containing a single number. This
           number specifies the absolute maximum number of recipients for a
           single message. If the Courier mail server receives a message with
           more recipients, the message is duplicated as often as necessary
           until each copy of the message has no more than batchsize
           recipients. If batchsize is missing, it defaults to 100 recipients
           per message.

       bofh
           This configuration file configures domain-based junk mail filters.
           Lines in this configuration files that begin with the # character
           are considered comments, and are ignored. The remaining lines
           contain the following directives, in any order:

           badfrom user@domain
               Reject all mail with the return address of <user@domain>.

           badfrom @domain
               Reject all mail with the return address of <anything@domain>.

           badfrom @.domain
               Reject all mail with the return address of
               <anything@anything.domain>.

           badfrom user@.domain
               Reject all mail with the return address of
               <user@anything.domain>.

           badmx N
               Reject all mail with a return address in any mail domain whose
               listed mail servers include server "N". "N" is an IP address.
               The BOFHCHECKDNS option in the esmtp configuration file must
               also be enabled (this is the default setting) in order for this
               additional checking to take place. Note that this is "best
               effort" check. A DNS failure to look up A records for hostnames
               returned in the MX record may hide the blacklisted server from
               view.

           freemail domain [domain2] [domain3]...
               Reject all mail with a return address <anything@domain> unless
               the mail is received from a mail relay whose hostname is in the
               same domain. "domain2" and "domain3" are optional, and
               specifies other domains that the mail relay's hostname may
               belong to. For example: "freemail example.com domain.com"
               specifies that mail with a return address @example.com will be
               accepted only from a mail relay with a hostname in the
               example.com or domain.com domain. Note that this setting
               requires that DNS lookup be enabled for incoming ESMTP
               connections (which is the default setting).

           spamtrap user@domain
               Reject all mail that has <user@domain> listed as one of its
               recipients.

                   Note
                   For local mailboxes, 'domain' must be set to the contents
                   of the me configuration file, or the server's hostname.
                   Also, this check is made after any alias processing takes
                   place. Suggested usage: create a single local spamtrap
                   account, then create aliases in the alias file that point
                   to the spamtrap account.

           maxrcpts N [hard]
               Accept the first N recipient addresses per message, maximum.
               The remaining recipients are rejected. An optional verbatim
               token "hard" specifies that the remaining recipients will
               immediately be returned as undeliverable (otherwise the
               remaining recipients are rejected as "temporary unavailable",
               and may be accepted on a later delivery attempt). If not
               specified, the first 100 recipients are accepted.

           opt BOFHCHECKHELO=1
               Verify the hostname provided in the ESMTP HELO/EHLO statement.
               "opt BOFHCHECKHELO=1" is a global default, which may be
               overridden by setting the BOFHCHECKHELO environment variable in
               the SMTP access file. See makesmtpaccess(8)[4] for more
               information.  "opt BOFHCHECKHELO=1" enables ESMTP HELO/EHLO
               checking by default, and ESMTP HELO/EHLO checking may be turned
               off for individual IP address ranges by setting BOFHCHECKHELO
               to 0 using makesmtpaccess(8)[4]. Alternatively, HELO/EHLO
               checking may be turned off by default, and enabled for specific
               IP address ranges by using makesmtpaccess(8)[4] to set
               BOFHCHECKHELO to 1. See makesmtpaccess(8)[4] for more
               information.

           opt BOFHHEADERLIMIT=n
               Reject messages whose headers exceed n bytes in size (minimum
               1,000 bytes, default 100,000 bytes).

           opt BOFHNOBASE64TEXT=1
               Reject messages with base64-encoded text/plain or text/html
               content.

           opt BOFHSPFHELO=keywords
               Use Sender Policy Framework to verify the HELO or EHLO domain
               sent by the connecting SMTP client. See Sender Policy Framework
               Keywords below for a list of possible keywords.

               SPF checking is not used for HELO or EHLO commands that specify
               an IP address instead of a domain name.

                   Note
                   This setting may be used in combination with opt
                   BOFHCHECKHELO=1. The BOFHCHECKHELO=1 check is disabled if
                   SPF verification of the HELO/EHLO results in the SPF status
                   of "pass". This makes sense: if the HELO/EHLO domains
                   complies with the domain's SPF, it is not necessary to
                   check it further.

           opt BOFHSPFMAILFROM=keywords
               Use Sender Policy Framework to verify the return address in the
               MAIL FROM command sent by the connecting SMTP client. See
               Sender Policy Framework Keywords below for a list of possible
               keywords.

                   Note
                   No SPF checking is done for if the MAIL FROM command
                   specifies an empty return address (a bounce). There's
                   nothing to check.

           opt BOFHSPFFROM=keywords
               Use Sender Policy Framework to verify the return address in the
               From: header. See Sender Policy Framework Keywords below for
               important information, and a list of possible keywords.

           opt BOFHSPFHARDERROR=keywords
               This setting lists the unacceptable SPF results that should
               result in a permanent error. All other unacceptable SPF results
               are kicked back with a temporary error indication, inviting the
               sender to try again later.

               The default setting for BOFHSPFHARDERROR is fail,softfail.

           opt BOFHSPFTRUSTME=1
               Disable all SPF checks for any connecting client that has
               relaying privileges (RELAYCLIENT is explicitly set, or
               inherited after a successful SMTP authentication).

           opt BOFHSPFNOVERBOSE=1
               This setting disables custom SPF rejection messages. Any SPF
               rejection message specified by the SPF policy is replaced by a
               stock, bland message. The author of this SPF implementation
               believes that there's a minor security issue with letting an
               external site control the error messages issued by your mail
               server. The same author does not believe that this is such a
               big deal, but security-sensitive minds may choose to enable
               this setting, and sleep easy at night.

           opt BOFHSUPPRESSBACKSCATTER=list
               This is one of the two settings that controls which messages
               are subject to backscatter suppression. The other setting,
               ESMTP_BLOCKBACKSCATTER is set in the courierd configuration
               file, which contains further documentation.

               "list" is a comma-separated list of message sources. The
               possible message sources are:

               authsmtp
                   Messages received via SMTP from clients with relaying
                   privileges (authenticated SMTP, or IP addresses that always
                   have relaying privileges.

               smtp
                   All other messages received via SMTP.

               none
                   Do not suppress backscatter messages from any source.

               The default setting is "opt BOFHSUPPRESSBACKSCATTER=smtp". The
               other possible values are "opt
               BOFHSUPPRESSBACKSCATTER=smtp,authsmtp" (which suppresses
               backscatter from all SMTP mail), and "opt
               BOFHSUPPRESSBACKSCATTER=none".

       calendarmode
           This configuration file enables basic calendaring features in the
           webmail server. Calendaring is currently considered experimental in
           nature, and the current implementation provides basic calendaring
           services. If this file does not exist, calendaring options are
           disabled. If this file exists it should contain a single word:
           "local". For example:

               echo "local" >/etc/courier/calendarmode
           This configuration file must be globally readable, so make sure
           that your umask is not set too tight.

       courierd
           This configuration file specifies several parameters relating to
           general the Courier mail server configuration. A default
           configuration file will be installed, and you should consult its
           contents for additional information.

       defaultdomain
           This file contains one line whose contents is a valid mail domain.
           Most header rewriting functions will append @defaultdomain to all
           E-mail addresses that do not specify a domain. If defaultdomain is
           missing, the Courier mail server uses the contents of the me
           control file.

           When the ESMTP server receives a "RCPT TO" command containing the
           address <user@[ip.address]>, and the IP address is the same as the
           IP address of the socket it's listening on, the ESMTP server
           replaces the IP address with the contents of the defaultdomain
           control file. If defaultdomain is missing, the Courier mail server
           uses the contents of the me control file.

           The contents of defaultdomain are also appended to return addresses
           to mail sent from the Courier mail server's webmail server, if they
           don't already have a domain. If defaultdomain does not exist, the
           Courier mail server's webmail server obtain the machine hostname,
           and uses that.

               Note
               The mail domain in defaultdomain should be one of the local
               domains, as defined by the locals and the hosteddomains control
               files.

               Otherwise, if a domain-less address in mail headers gets
               augmented with defaultdomain and the recipient replies to the
               message, upon receipt Courier won't recognize the recipient
               address as a local mailbox. This might not necessarily be
               wrong, but the consequences of such an action must be clearly
               understood.

               Warning
               If you change the contents of this configuration file, it may
               be necessary to rerun the makealiases command again, else your
               mail will promptly begin to bounce. If you don't have this
               configuration file defined, and you change the system's network
               host name, you may also need to run makealiases.

       dotextension
           This file contains one line whose contents specify the name of
           dot-files in users' home directories which contain delivery
           instructions. If this file does not exist, the Courier mail server
           reads $HOME/.courier, $HOME/.courier-foo, $HOME/.courier-default,
           and so on. If this file contains the text "qmail", the Courier mail
           server will instead read $HOME/.qmail, $HOME/.qmail-foo,
           $HOME/.qmail-default, and so on.

       dsnfrom
           This file contains one line specifying the contents of the From:
           header that the Courier mail server puts in all delivery status
           notifications. This file specifies a complete header, except for
           the "From: " part. If dsnfrom is missing, then the Courier mail
           server uses the following header: "Courier mail server mail server
           at me" <@>

       dsnlimit
           Maximum size, in bytes, of a message whose contents are included in
           delivery status notifications. By default, the entire message is
           only included in non-delivery notices (failures). Only the headers
           will be returned for delay notifications (warnings) and return
           receipts; or for failures if the original message is larger than
           dsnlimit. If missing, dsnlimit is set to 32K.

           The sender can request that the entire message be returned even on
           delayed notices or return receipts, however the Courier mail server
           will ignore this request if the message size exceeds this limit.

       enablefiltering
           This configuration file enables the global mail filtering API for
           selected mail sources. This file, if it exists, contains a single
           line of text that specifies which kind of mail will be filtered.
           The possible values are:

           esmtp
               Enables global mail filtering for mail received via ESMTP.

           local
               Specifies that mail received from logged on users, via
               sendmail, and mail forwarded from dot-courier(5)[5] will be
               filtered using the global mail filtering API.

           uucp
               Specifies that mail received from UUCP will be filtered.

           If you want to specify more than one source of mail, such as ESMTP
           and local mail, specify both esmtp and local, separated by a space
           character.

               Note
               The global mail filtering API is described, in detail, in the
               courierfilter(8)[6] manual page. This is NOT the traditional
               user-controlled mail filtering, such as maildrop(1)[7]. A
               global mail filter is a daemon process that selectively accepts
               or rejects incoming mail, based on arbitrary criteria.

       esmtpacceptmailfor
           This file lists all domains that the Courier mail server accepts
           mail for via ESMTP. This file is in the same format as the locals
           file. If this file is missing, the Courier mail server uses the
           single domain specified in me (or the system machine name).

       esmtpacceptmailfor.dat
           This is a binary database file that lists additional domains that
           the Courier mail server accepts mail for, just like
           esmtpacceptmailfor. A binary database file will be faster than a
           flat text file when the number of domains is large. The Courier
           mail server will accept mail for domains listed in either
           esmtpacceptmailfor or esmtpacceptmailfor.dat.
           esmtpacceptmailfor.dat is created by the makeacceptmailfor command.
           You can use both esmtpacceptmailfor.dat and esmtpacceptmailfor at
           the same time. Put your most popular domains in esmtpacceptmailfor,
           and put the rest of them into esmtpacceptmailfor.dat.

       esmtpauthclient
           This configuration file configures ESMTP authentication for the
           ESMTP client. This is a text file of zero or more lines that
           contain the following fields:

               relay userid password
           When the Courier mail server connects to a remote ESMTP relay, the
           Courier mail server will authenticate itself using userid and
           password. These fields are separated by one or more whitespace
           characters. Because this file contains passwords, it must not be
           world or group readable, and owned by the user "daemon".

           ESMTP negotiation will take place, and the Courier mail server will
           use a SASL authentication method supported by both the Courier mail
           server and the remote ESMTP server. Currently the Courier mail
           server supports PLAIN, LOGIN and CRAM-MD5 authentication. CRAM-MD5
           is preferred over the other two, and PLAIN is preferred over LOGIN.

           The Courier mail server also supports ESMTP over SSL (the ESMTP
           STARTTLS extension). If ESMTP STARTTLS is enabled, STARTTLS will be
           used to establish a secure link first. The authentication will take
           place afterwards, over a secure channel.

           Changes to this file take effect, more or less, immediately
           (existing connections are not affected, but new connections will
           read the updated data).

       esmtpd
           This file is used to initialize the environment and parameters for
           courieresmtpd. A default file will be provided during installation.
           See the comments in the file for more information. For changes to
           this file to take effect you run the esmtpd stop command followed
           by esmtpd start.

       esmtpdelay
           This file contains one line of text that specifies how long
           courieresmtp waits after a failure to contact the remote mail
           server before another attempt is made.  courieresmtp (not to be
           confused with courieresmtpd) delivers outgoing mail to remote mail
           servers. The timeout is specified as an integral number, optionally
           followed by m - minutes, or h - hours. Otherwise it is specified in
           seconds.

           The courieresmtp process delivers mail that's routed to external
           mail relays, via ESMTP. When attempting to initally contact a mail
           server courieresmtp waits for the amount of time specified by
           esmtptimeoutconnect (see below).  esmtptimeoutconnect is usually
           set to a relatively long period of time, in order to accomodate
           slow mail servers. A large number of messages queued up for an
           unreachable mail server can tie up delivery slots that can be put
           to a better use by reassigning them for mail to another domain.
           Although the Courier mail server does not usually assign all
           delivery slots for messages to the same domain (this is a tuneable
           parameter), it is still not very healthy to have a bunch of
           courieresmtp daemons spinning their wheels, doing nothing.

           The situation worsens when there is a large number of mail relays
           that accept mail for the same domain, and all of them are
           unreachable due to a network failure. That's because the
           esmtptimeout waiting period is used for each individual mail relay.
           Multiply esmtptimeout by the number of servers to see how large the
           delay really will be.

           esmtpdelay is implemented internally in the courieresmtp module.
           The main the Courier mail server scheduling daemon is not aware of
           what's happening internally in courieresmtp. When courieresmtp
           fails to contact any mail relay for the domain, the message is
           postponed, and the esmtpdelay timer is set. Any additional messages
           received by the same courieresmtp daemon (for the same domain), are
           immediately postponed without any attempt to contact a remote mail
           relay. When the amount of time set by esmtpdelay expires,
           courieresmtp will attempt to make another delivery attempt as
           usual.

           If esmtpdelay does not exist, the default delay is five minutes.
           Any messages that are postponed look like any other temporary
           failure to courierd. Delivery attempts are rescheduled as if a real
           temporary failure took place. Therefore it does not make sense to
           set esmtpdelay to be greater than retryalpha (see below). When
           retryalpha is smaller is esmtpdelay, you'll just messages spinning
           through the mail queue, with useless delivery attempts being
           attempted because esmtpdelay still hasn't expired.

           Occasionally you might observe somewhat strange behavior on systems
           with heavy mail traffic.  esmtpdelay applies separately to each
           individual instance of courieresmtp. When a remote mail server
           keeps going up and down, it is possible to end up with multiple
           courieresmtp daemons handling mail for the same domain, but only
           some of them will encounter a network failure, purely by the luck
           of the draw. The remaining daemons will be able to establish a
           connection. So you'll end up with some courieresmtp daemons being
           able to deliver mail immediately, while the rest are still waiting
           patiently for esmtpdelay to expire, postponing all messages in the
           meantime. Some messages - but not all - will be immediately
           postponed without a delivery attempt, becauses they ended up
           getting to a daemon which is waiting for esmtpdelay to expire.

           Another anomalous situation may happen when a courieresmtp daemon
           gets reassigned to another domain, and then receives more mail for
           the previous domain. This can happen when you have a lot of mail
           going through. Although the Courier mail server tries to shuffle
           all mail for same domain into one pile, the scheduler still tries
           to dispatch mail on "first-come, first-serve" basis, as much as
           possible. When that happens another delivery attempt will be made
           immediately, because the previous esmtpdelay was cancelled when the
           daemon got reassigned to another domain.

           There can also be occasional abnormalities that affect systems with
           light traffic. When there is a domain with several mail relays of
           equal priority, one mail relay is chosen at random for the
           connection attempt. If some of the equal-priority mail relays are
           unreachable and a courieresmtp daemon picks it, it will start the
           esmtpdelay timer and refuse to deliver any more mail until it
           expires, even if most of the mail servers are functional. This will
           happen only with mail relays of the lowest priority. Otherwise,
           courieresmtp will always try to contact another mail relay of a
           still lower priority, before giving up and setting the esmtpdelay
           timer. Another courieresmtp daemon will not be started for the same
           domain if there's already an existing one, so all delivery attempts
           will be turned away until esmtpdelay expires. Another courieresmtp
           daemon will be started only in the event of multiple simultaneous
           delivery attempts that happen to coincide at the same time.

           This is somewhat mitigated by the fact that all courieresmtp
           daemons are killed after a short period of total inactivity
           (currently one minute), so that longer intervals specified by
           esmtpdelay are ignored. Note, however, that receiving a message to
           deliver, and then postponing it immediately, does count as some
           activity.

           esmtpdelay can be turned off by setting it to 0 seconds.
           esmtpdelay is designed for servers that handle heavy amount of mail
           that wish to avoid having outbound delivery slots tied up due to
           network failures, at an expense of an occasional anomalous behavior
           due to harmless paranoia.  esmtpdelay may prove to actually make
           things worse for systems that carry only light mail traffic, if
           they are burdened with a task of exchanging mail primarily with
           external systems that are not properly maintained.

       esmtpgreeting
           The complete greeting banner displayed by courieresmtpd. Changes to
           this file take effect immediately.

       esmtphelo
           This file contains one line of text, what the Courier mail server
           calls itself in the EHLO or HELO command sent to a remote SMTP
           server.  me is used if this file does not exist.

           esmtphelo may also be set to a special value of "*":

               echo '*' >esmtphelo
           (Note the single quotes, to prevent "*" from being expanded by the
           shell). The Courier mail server will take the IP address of the
           local side of the connection to the remote SMTP server, look up the
           IP address in DNS, and use the hostname from the reverse DNS
           lookup. This might be useful when the Courier mail server server is
           multihomed. The Courier mail server will look up the local IP
           address of each individual connection, and use that in its EHLO or
           HELO command.

               Note
               Functioning DNS is required. Using the hosts file, or an
               equivalent, won't work. This function uses the Courier mail
               server's native DNS resolver, which reads /etc/resolv.conf and
               queries the listed DNS servers directly.

       esmtproutes
           This file is used by the ESMTP module, and it contains one or more
           lines in the following form:

               domain:relay[,port][/SECURITY=STARTTLS][/SECURITY=NONE]

           domain is any SMTP domain.  relay specifies a fixed mail relay for
           this domain.  relay is optionally followed by a comma and a port
           number, to specify a port other than the default port 25. If an
           address's domain is not found in esmtproutes, the Courier mail
           server looks for MX and A records as usual (and always delivers to
           port 25). If the domain is found in esmtproutes, however, any MX or
           A records for the domain are ignored; instead the Courier mail
           server delivers the message to the specified relay.

           relay can be another domain, or an explicit IP address inside
           brackets. For example, if esmtproutes contains the following:

               example.com: relay.domain.com
               domain.com: [192.168.0.2]
           Mail for example.com is delivered to relay.domain.com, ignoring any
           MX records for example.com. Mail for domain.com will be delivered
           to the machine at IP address 192.168.0.2. All other domains will
           have their MX and A records looked up.

               Note
               Unlike Qmail, the Courier mail server looks up MX and A records
               for relay.example.com (Qmail only looks up A records).
           esmtproutes may contain comments, any line that starts with the #
           character is ignored. Also, wildcards are allowed:

                .example.com: [192.168.0.3],26
           This specifies that any address of the form
           <anything@anything.example.com> will be delivered to the mail
           server at this IP address, but on port 26.

           esmtproutes is read from top to bottom, stopping as soon as a first
           match is found.

           domain may be empty, this specifies a smarthost for all domains.
           For example, if esmtproutes contains the following text:

               example.com: relay.example.com
                       :[192.168.0.4]
           This specifies that all mail to example.com is rerouted to
           relay.example.com. All other mail is routed to the IP address
           192.168.0.4.

           If relay is empty, the Courier mail server interprets it as an
           explicit directive to use MX and A records from DNS. For example:

               example.com:
               :[192.168.0.4]
           This uses MX and A records for all messages to example.com. All
           other mail is rerouted to the IP address 192.168.0.4.

           The optional /SECURITY=STARTTLS flag indicates that mail to this
           domain should be automatically upgraded to use the SECURITY ESMTP
           extension. See the Courier mail server installation notes for a
           description of SECURITY, what it does, and how to configure it.

           The /SECURITY=NONE flag prevents the Courier mail server from using
           the STARTTLS ESMTP extension even if the remote server claims to
           support it. Use this flag to deliver mail to misconfigured
           Microsoft Exchange relays that claim to support STARTTLS, but
           always report a failure to a STARTTLS request.

           Changes to this file take effect immediately, more or less.
           Existing courieresmtp processes that already have an established
           connection will ignore any changes.

       esmtptimeout
           This file contains one line of text that specifies the timeout for
           an SMTP command. The timeout is specified as an integral number,
           optionally followed by m - minutes, or h - hours. Otherwise it is
           specified in seconds. This timeout is used for all SMTP commands,
           unless the SMTP command has a dedicated timeout defined by a
           different configuration file. The default timeout is ten minutes.

       esmtptimeoutconnect
           This file contains one line of text that specifies the timeout for
           an SMTP connection attempt. Most TCP/IP stacks wait an
           extraordinary long period of time for SMTP connections to go
           through. This configuration setting limits the amount of time the
           Courier mail server waits for the SMTP connection to complete. The
           default timeout is one minute. Set esmtptimeoutconnect to 0 in
           order to use whatever default timeout your TCP/IP stack uses.

       esmtptimeoutdata
           This file contains one line of text that specifies the timeout for
           transferring the message contents or individual replies. The
           default timeout is five minutes. You WILL HAVE TO bump this up if
           you're on a slow link, and you want to send large messages. A
           28.8Kbps link can be optimistically expected to push 3,000 bytes
           per second. With a five minute cutoff, you will not be able to send
           or receive anything larger than about 870 Kb. You have no business
           sending or receiving 870 Kb messagesl, if all you have is an analog
           28.8Kbps connection.

       esmtptimeouthelo
           This file contains one line of text that specifies the timeout for
           the initial EHLO or HELO command. The Courier mail server will wait
           this amount of time to receive the initial greeting banner from the
           remote SMTP server, and a response to the subsequent EHLO/HELO
           command. The default value is 5 minutes.

       esmtptimeoutkeepalive
           This file contains one line of text that specifies how often
           outbound SMTP sessions are kept idle after delivering a message.
           After the Courier mail server connects to an SMTP server and
           completes the attempt to deliver the message, the SMTP session is
           kept idle for this time interval before being shut down. If the
           Courier mail server receives another message for the same domain,
           it will be delivered using the existing SMTP session, instead of
           establishing a new one. Note that some SMTP servers have a very
           short idle timeout, Qmail's is only two minutes. The default value
           is 60 seconds.

           Note that there's also a separate limit to the maximum number of
           simultaneous SMTP sessions to the same domain. That limit is
           currently four, which is adequate for nearly every situation, so
           for now it will be set by an undocumented configuration file.

       esmtptimeoutkeepaliveping
           This file contains one line of text that specifies how often the
           Courier mail server will issue a useless RSET command when the
           connection is idle (see esmtptimeoutkeepalive). While waiting for
           any more messages to deliver to the same domain, or for the
           esmtptimeoutkeepalive interval to expire, courieresmtp will
           transmit RSET commands at regular intervals specified by this
           configuration file. The default value is 0 seconds, which turns off
           the keepalive ping altogether. This configuration settings must be
           for a shorter time interval than esmtptimeoutkeepalive for it to
           make any sense. Note that other system administrators may consider
           this to be a very rude thing to do. Also keep in mind that this may
           generate quite a bit of idle traffic. If you have the Courier mail
           server configured for a maximum number of 200 outbound SMTP
           sessions and a 30 second esmtptimeoutkeepaliveping setting, then
           you can have as much as an average of around seven pings every
           second!

       esmtptimeoutquit
           This file contains one line of text that specifies how long the
           Courier mail server waits for the external SMTP server to
           acknowledge the QUIT command, before the Courier mail server
           unilaterally tears down the connection. The default value is 10
           seconds. This must be a small value because the Courier mail server
           needs to be able to shut down quickly, on very short notice.

       faxqueuetime
           This file specifies how long the Courier mail server normally tries
           to repeatedly resend a fax message (if the courierfax module is
           enabled). The default E-mail message retry timeout (the queuetime
           setting) is one week, which is a reasonable timeout value for
           E-mail messages (taking into account downed circuits, or crashed
           servers). However, it doesn't make sense to keep trying to
           redeliver fax messages for a whole week.

           faxqueuetime specifies the timeout for fax messages. This time
           interval is specified in the same way as queuetime (see queuetime
           for more information).

       faxnotifyrc
           This file specifies which mailbox the Courier mail server should
           deliver received faxes (if this option is enabled). See the Courier
           mail server's installation notes for more information.

       faxrc
           This file configures the Courier mail server's outbound faxing and
           dialing parameters. Consult the comments in the default file for
           additional information, and the courierfax(8)[8] manual page for
           more information.

       hosteddomains
           This file lists locally-hosted domains. It is very similar in
           function to the locals control file. Any address with a domain
           listed in hosteddomains is considered to be a local address. The
           difference between hosteddomains and locals is that domains listed
           in hosteddomains are not removed from individual addresses before
           looking up the location of their mailboxes. For example, if the
           domain "example.com" appears in locals, the address
           user@example.com will have example.com removed, and then the
           Courier mail server will look for a local mailbox named "user".

           If the domain "example.com" appears in hosteddomains instead, the
           Courier mail server will look for a local mailbox named
           "user@example.com" instead.

           The contents of the hosteddomains configuration file is a list of
           domains, one per line, in lowercase. You must run the
           makehosteddomains command for any changes to take effect.

           Additionally, hosteddomains can specify simple domain aliases. See
           the complete description in the makehosteddomains(8)[9] manual
           page.

       ldapaddressbook
           This file is used by the webmail server. It contain a default
           systemwide list of accessible LDAP address books. A default file
           will be installed, listing some common Internet address books. Each
           line in this file contains the following information:

               name<tab>host<tab>port<tab>suffix<tab>binddn<tab>bindpw
           "<tab>" is the ASCII tab character.  "name" is the unique name for
           this LDAP server.  "host" and "port" specify the connection
           parameters.  "suffix" specifies the root LDAP entry whose subtree
           gets searched. The "binddn" and "bindpw" fields are not presently
           used (they were used in earlier version of the webmail server,
           before the LDAP search interface was rewritten and simplified).

       ldapaliasrc
           This file is used by the courierldapaliasd process. See
           courierldapaliasd(8)[10] for more information.

       locallowercase
           If this file exists, the Courier mail server will not distinguish
           being lowercase and uppercase local accounts, so that
           john@example.com and John@example.com will refer to the same local
           mailbox (where example.com is your domain).  Postmaster,
           postmaster, and POSTMASTER always refer to the same account, even
           if locallowercase does not exist.

               Note
               If locallowercase exists you cannot have any system accounts
               that contain uppercase letters.  locallowercase applies only to
               local mail. Mail addressed to external domains will always have
               the case of the addresses preserved.

       locals
           This file contains one or more lines of text, where each line
           contains a valid mail domain. Any E-mail address without @domain,
           or with a domain that can be found in locals will be considered to
           be an address of a local mailbox. A domain can be specified with a
           leading dot:

                .domain.com
           This is called a "wildcard". Any domain ending in domain.com, such
           as a.domain.com, b.domain.com, a.b.c.domain.com - but NOT
           somedomain.com - will be considered local. Note that domain.com is
           NOT included in this wildcard. Both "domain.com" and ".domain.com"
           should be listed.

           Specific hosts can be excluded from the wildcard. Example:

                !host.domain.com
                .domain.com

           anything.domain.com is considered to be a local domain, except for
           host.domain.com. Note that "!host.domain.com" must appear in locals
           before the .domain.com wildcard.

           The "!hostname" syntax is also valid in the esmtpacceptmailfor
           control file.

           If locals does not exist, the Courier mail server uses the contents
           of the me control file (note that me specifies only one domain,
           second and subsequent lines are ignored). Also, see hosteddomains.

       localtimeout
           This file specifies the watchdog timer for local mail deliveries.
           If a local mail delivery attempt does not complete in the
           proscribed time interval, the delivering process ID is killed. The
           time interval in localtimeout is specified in the same way as
           queuetime (see queuetime for more information).

       logindomainlist
           If this file exists then the webmail login screen will have a
           drop-down list whose contents will be read from this file. This
           file should contain a list of E-mail domains, one per line. It
           should be created if the Courier mail server's webmail server is
           used to provide mail access for more than one domain. Instead of
           typing "user@domain" to log in, it will only be necessary to enter
           "user", and select the domain from the drop-down list. If this file
           does not exist it will be necessary to enter the full E-mail
           address into the webmail login screen.  The enhanced
           logindomainlist makes it possible to specify a separate list of
           domain for each virtual web site, and more control over the
           defaults.

           What if you don't want to display a drop down menu? Administrators
           can now specify records that generate a hidden field in login.html,
           or an editable text field, allowing sqwebmail to show only one mail
           login domain to each user per access URL or IP address. This
           functionality can greatly reduce confusion for first time webmail
           users, and greatly speed the login process for frequent webmail
           users.

           Finally, the new logindomainlist file offers a new tool to ease
           maintenance. Administrators can now use wildcards to "rewrite" the
           domain portion of the access URL to the mail domain equivalent. For
           example, the following record can rewrite the URL "mail.*.com" to
           the mail domain "*.com"

           *.com:mail.*.com:@

           This powerful wildcard functionality can ease the login process for
           most of your server's mail domains with just one or two
           logindomainlist records.

           File Format
               Let's take a look at the NEW logindomainlist file format:

               firstfield:secondfield:thirdfield

               Above, we can see that the new logindomainlist records are made
               up of three fields delimited by colons. But what does each
               field do?

               First Field - the first field contains the "mail domain" for
               which we would like the user to log in under. The mail domain
               is the part of an email address after the @ symbol. For
               example, in the email address "user@domain.com", "domain.com"
               is the mail domain.

               Second Field - the second field contains the "access domain".
               The access domain contains an URL or IP address that is used to
               figure out which mail domain to use by default. For example, in
               the following logindomainlist record:

               domain1.com:domain2.com

               "domain2.com" is the "access domain" and "domain1.com" is the
               "mail domain". If the user logs into the following URL:

               http://domain2.com/cgi-bin/sqwebmail

               His default "mail domain" will be "domain1.com".

               Third Field - the third field may contain a modifier. The
               modifier may be either a single character modifier, or a group
               identification string. The single character modifiers and the
               group modifier are described in detail below.

               Finally, the logindomainlist file may also contain comments and
               empty lines. Empty lines can be used to group records visually,
               and comments can be used to explain why a certain record or
               group of records look the way they do.

               If the first character of a line is a '#', then the entire line
               is considered a comment and is ignored. If the first character
               of a line contains whitespace, the entire line is assumed to be
               an empty line and is ignored.

           Modifiers

               @ - the '@' modifier can be used to create a hidden field on
               the login.html page which contains the default mail domain. In
               addition, this field will automatically display the default
               mail domain in plain text to the right of the userid text box.

                   Note
                   The '@' modifier ALLOWS the use of wildcards to automate
                   the relationship between "access domains" and "mail
                   domains". See the heading "Wildcards" below for more
                   information about wildcarding.
               - - the '-' modifier can be used to create an editable text
               field on the login.html page which contains the default mail
               domain.

                   Note
                   The '-' modifier ALLOWS the use of wildcards to automate
                   the relationship between "access domains" and "mail
                   domains". See the heading "Wildcards" below for more
                   information about wildcarding.
               group string - If no modifier is specified in the third field,
               or if the third field modifier is a group identifier string,
               then a drop down menu will be displayed on the login.html page.
               Records with the SAME group string will be displayed together
               in the drop down. For example, if your logindomainlist file
               contains the following records:

                        domain1.com:domain2.com:firstgroup
                        domain3.com:domain4.com:firstgroup
                        domain5.com:domain6.com:firstgroup
                        domain7.com:domain8.com:secondgroup
                        domain9.com:domain10.com:secondgroup
               And the user logs into sqwebmail with the following URL:

               http://domain4.com/cgi-bin/sqwebmail

               He will see a drop down containing ONLY the following domains:

                        domain1.com
                        domain3.com
                        domain5.com
               "domain3.com" will be automatically selected, or defaulted.
               Only the records in the firstgroup will be visible to the user.
               This functionality is great for organizations with more than
               one mail domain.

                   Note
                   The group string modifier does NOT allow the use of
                   wildcards to automate the relationship between "access
                   domains" and "mail domains". This is because drop down
                   menus are fundamentally incompatible with wildcards.

           Wildcards
               If a record's modifier allows wildcarding (See "Modifiers"
               above for information about which modifiers allow wildcarding
               and which do not.) then the first and second fields of that
               record _MAY_ contain wildcards. Wildcards match against the
               HTTP_HOST CGI environment variable only.  IP addresses can NOT
               be used if either the first or second fields contain the
               wildcard character. However, if neither the first nor second
               fields contain the wildcard character, then the second field
               can contain an IP address.

               In the logindomainlist file, an asterisk (*) character in
               either the first and/or second field represents a wildcard. Any
               asterisk in the second field will be used to match an access
               domain. If an asterisk exists in the first field then any
               characters which the asterisk in the second field represents
               will replace the asterisk in the first field when sqwebmail
               determines the default mail domain. However, asterisks are not
               required in either the first or second fields. They are totally
               optional. For example, given the following logindomainlist
               record:

               *.com:mail.*.com:@

               If the user logs into sqwebmail with the following URL:

               http://mail.mydomain.com/cgi-bin/sqwebmail

               The asterisk in the second field will represent the string
               "mydomain". This string will then replace the asterisk in the
               first field to give the following default mail domain:
               mydomain.com

               Similarly, if the following record exists in the
               logindomainlist file:

               *:*:@

               Then ANY URL the user uses to access sqwebmail will be
               automatically used for the default mail domain.

               But the first field doesn't _HAVE_ to contain an asterisk. The
               following will work just fine:

               mydomain.com:mydomain.*:@

               The above example will allow the user to access the
               "mydomain.com" mail domain from any of the following URLs:
               "mydomain.org", "mydomain.net", "mydomain.us", etc...

               And finally, the first field doesn't have to contain anything
               at all! If the first field is empty, that record will serve as
               an explicit no-default mail domain. No default mail domain will
               be specified if the second field matches the user's login URL.
               This is useful because the logindomainlist is searched from the
               top down. Any wildcard records at the bottom of the list will
               be overridden by records closer to the top. An "explicit
               no-default" record can be used to specify certain domains as
               "system account" domains so that no default mail domain is
               specified.

       maildirfilterconfig
           This file, if exists, sets the global defaults for mail filtering
           in the webmail server. Mail filtering in the webmail server is a
           subject worthy of special mention. A full description of how to
           install and configure webmail-based mail filtering is included in
           the installation notes for the Courier mail server. Refer to the
           installlation instructions for additional information.

       maildirshared
           This file, if exists, specifies the location of shared maildirs for
           the webmail and IMAP server. Normally, each mailbox must be
           separately configured to access every shared maildir, by the
           maildirmake(1)[11] command. This file allows shared maildirs to be
           set globally for everyone. Everyone's webmail and IMAP server will
           pick up the shared maildirs specified in this file. See
           maildirmake(1)[11] for more information.

       maildrop
           This file contains one line whose contents is a pathname to the
           maildrop(1)[7] mail delivery agent. If the Courier mail server
           knows that the delivery agent used to delivery mail locally is
           maildrop(1)[7] then certain delivery optimizations are possible.
           This configuration file does NOT actually specify that
           maildrop(1)[7] should be used as a local mail delivery agent, it
           only specifies where maildrop(1)[7] is installed. The default local
           mail delivery instructions are specified in the courierd
           configuration file. If the specified delivery instruction specify
           running an external program whose pathname matches the one
           specified by this configuration file, the Courier mail server
           assumes that it's maildrop(1)[7], and will use maildrop-specific
           options to optimize mail delivery.

           This configuration file is initialized, by default, to point to the
           version of maildrop(1)[7] that's integrated with the Courier mail
           server. The integrated version of maildrop(1)[7] is configured
           slightly differently than the standalone version of maildrop(1)[7].

           Although you can set the maildrop configuration file to point to
           some other version of the maildrop mail filter, you MUST set the
           maildropfilter configuration file (see below), to point to the
           integrated version of maildrop.

       maildropfilter
           This file contains one line whose contents is a pathname to the
           maildrop(1)[7] mail delivery filter. In addition to being a
           delivery agent, maildrop can also be used as a mail filtering
           engine. If this file exists, the Courier mail server will be
           capable of invoking recipient-specified mail filters when a message
           is received. If the mail filtering rules reject the message, the
           Courier mail server will not accept the message for delivery. This
           means that when receiving mail via ESMTP, the Courier mail server
           will reject the ESMTP transaction without even accepting the
           message from the remote mail server.

           This file is not installed by default. To activate mail filtering
           for local recipients, simply copy the contents of the maildrop
           configuration file to maildropfilter.

       maildroprc
           This file contains systemwide mail filtering instructions for
           maildrop(1)[7] deliveries. This configuration file is optional, and
           is used by maildrop(1)[7] when it is invoked as a traditional
           post-delivery mail filter. See maildropfilter(6)[12] for more
           information.

       me
           This file contains one line whose contents is a valid machine name.
           When a single installation of the Courier mail server is shared
           over a network, each machine that's running the Courier mail server
           must have a unique me file. If me is missing, The Courier mail
           server uses the result of the gethostname() system call.

               Warning
               If you change the contents of this configuration file, it may
               be necessary to rerun the makealiases command again, else your
               mail will promptly begin to bounce. If you don't have this
               configuration file defined, and you change the system's network
               host name, you may also need to run makealiases.

       msgidhost
           If a message does not have a Message-ID: header, the Courier mail
           server may decide to create one. The host portion of the new header
           will be set to the contents of msgidhost, which contains one line
           of text. If msgidhost does not exist, me will be used in its place.
           Changes to this file take effect immediately.

       nochangingfrom
           The Courier mail server's webmail server lets the contents of the
           From: header be set for mailed messages. If this configuration file
           exists, the ability to set the contents of the From: header is
           disabled.

       queuelo, queuehi, queuefill
           These configuration settings tune the Courier mail server's mail
           queue processing. The Courier mail server does not load the entire
           mail queue metadata in memory.  queuelo contains a number that
           specifies the queue "low watermark" message count.  queuehi
           contains a number that specifies the queue "high watermark" message
           count.  queuefill specifies a time interval, "queue refill" in
           seconds. The number in queuefill may optionally be followed by "m",
           indicating that the queue refill is specified in minutes.

           queuehi specifies the maximum number of messages that are loaded
           into memory. The Courier mail server reads the mail queue on disk
           until either it reads all of it, or it reads the number of messages
           specified by queuehi. As messages are delivered they are removed
           from the memory and disk. Messages that are deferred for another
           delivery attempt are removed from memory, but kept on the disk.

           When the number of messages in memory falls below queuelo, The
           Courier mail server goes back to disk and attempts to fill the
           memory queue to the top, again.

           This is, basically, a capsule summary of the mail queue processing
           logic. Many small, low level details are omitted; this is just an
           executive overview. When new messages arrive during a large mail
           backlog, the new messages are also loaded into the memory queue, if
           there's room for them. Therefore, during a large mail backlog the
           Courier mail server simultaneously tries to clear the existing
           backlog, and process any new mail at the same time. Up to the
           Courier mail server 0.41, all of this generally translates to the
           Courier mail server giving priority to newly arrived mail, and
           processing the backed up mail queue if spare resources are
           available.

           The queuefill setting was added in the Courier mail server 0.42, in
           an attempt to keep new mail from excessively delaying existing mail
           during a major queue backup.  queuefill specifies a time interval.
           When the Courier mail server completely fills the memory queue it
           sets a timer. After the interval given by queuefill The Courier
           mail server will go back and re-fill the mail queue even if the
           number of messages did not fall below the low watermark. If the
           Courier mail server finds older messages in the mail queue they
           will be pushed to the top of the scheduling queue, and given
           priority.

           Smaller queuefill time intervals means more frequent trips to the
           disk, and more overhead. But, in exchange for that, during a mail
           backlog the Courier mail server will spend more time handling a
           greater number of delayed messages. Larger queuefill time intervals
           means less frequent trips to the disk, and less overhead, in
           exchange for less "fairness" during large mail backlogs.

           queuefill defaults to five minutes, if not specified. Explicitly
           setting it to 0 seconds turns off the queue re-filling completely,
           essentially reverting to pre-0.42 behavior. The default queuelo and
           queuehi values are computed at run time.  queuelo defaults to the
           larger of 200, and the sum total of configured mail delivery slots,
           both local and remote.  queuehi, if not explicitly set, defaults to
           the smaller of twice the queuelo, or queuelo plus 1000.

       queuetime
           This file specifies how long the Courier mail server normally tries
           to repeatedly deliver a message, before giving up and returning it
           as undeliverable. Messages are immediately returned as
           undeliverable when a permanent failure is encountered (such as the
           recipient address not being valid). Attempts to deliver the message
           when there's a temporary, transient, error (such as the network
           being down) will be repeatedly made for the duration of time
           specified by this configuration file. This file contains a number
           followed by the letter 'w' for weeks, or 'd' for days. It is also
           possible to use 'h' for hours, 'm' for minutes, or 's' for seconds.
           Only integers are allowed, fractions are prohibited. However, you
           can use '1w2d' to specify one week and two days. If queuetime is
           missing, the Courier mail server makes repeated delivery attempts
           for one week.

       retryalpha, retrybeta, retrygamma, retrydelta
           These control files specify the schedule with which the Courier
           mail server tries to deliver each message that has a temporary,
           transient, delivery failure.  retryalpha and retrygamma contain a
           time interval, specified in the same way as queuetime.  retrybeta
           and retrymaxdelta contain small integral numbers only.

           The Courier mail server will first make retrybeta delivery
           attempts, waiting for the time interval specified by retryalpha
           between each attempt. Then, the Courier mail server waits for the
           amount of time specified by retrygamma, then the Courier mail
           server will make another retrybeta delivery attempts, retryalpha
           amount of time apart. If still undeliverable, the Courier mail
           server waits retrygamma*2 amount of time before another retrybeta
           delivery attempts, with retryalpha amount of time apart. The next
           delay will be retrygamma*4 amount of time long, the next one
           retrygamma*8, and so on.  retrymaxdelta sets the upper limit on the
           exponential backoff. Eventually the Courier mail server will keep
           waiting retrygamma*(2^retrymaxdelta) amount of time before making
           retrybeta delivery attempts retryalpha amount of time apart, until
           the queuetime interval expires.

           The default values are:

           retryalpha
               Five minutes

           retrybeta
               Three times

           retrygamma
               Fifteen minutes

           retrymaxdelta
               Three

           This results in the Courier mail server delivering each message
           according to the following schedule, in minutes: 5, 5, 5, 15, 5, 5,
           30, 5, 5, 60, 5, 5, then repeating 120, 5, 5, until the message
           expires.

       sizelimit
           Maximum size of the message, in bytes, that the Courier mail server
           accepts for delivery. The Courier mail server rejects larger
           messages. If sizelimit is set to zero, The Courier mail server
           accepts as large message as available disk space permits. If the
           environment variable SIZELIMIT is set at the time a new message is
           received, it takes precedence and the Courier mail server uses the
           contents of the environment variable instead. Changes to this file
           take effect immediately. The SIZELIMIT environment variable is for
           use by individual mail submission agents. For example, it can be
           set by the smtpaccess configuration file (see makesmtpaccess(8)[4]
           for more information) for mail from certain IP addresses.

           If sizelimit does not exist, and SIZELIMIT is not set, the maximum
           message size defaults to 10485760 bytes.

       submitdelay

           submitdelay specifies the delay before the first delivery attempt
           for a message that has been entered into the mail queue. Normally,
           the first delivery attempt is made as soon as possible. This
           setting delays the initial delivery attempt. It is normally used
           when you have a mail filter installed that detects duplicate
           messages arriving in a short period of time. If the mail filter
           detects this situation it can use the cancelmsg(1)[13] command to
           reject duplicate messages in the queue (and return them back to the
           envelope sender).

           submitdelay specifies a time interval in the same format as
           queuetime.

       usexsender
           If this configuration file exists, the Courier mail server's
           webmail server will set the X-Sender: header on all outgoing
           messages. This is a good idea if the webmail server allows the user
           to set the contents of the From: header. Note that the Courier mail
           server records the system userid of the sender in all locally-sent
           messages (which includes messages mailed by the webmail server),
           which is sufficient in most cases. In cases where you have many
           virtual accounts that share the same system userid, this
           configuration file provides a way to positively identify the sender
           of the outgoing message.

       uucpme

           uucpme sets the UUCP nodename of the Courier mail server mail
           relay. See courieruucp(8)[14] for more information.

       uucpneighbors

           uucpneighbors is used by the courieruucp module to specify the
           Courier mail server's configuration for relaying mail via UUCP. See
           courieruucp(8)[14] for more information.

       uucprewriteheaders
           If this file exists, headers of messages sent to/from UUCP
           addresses will be rewritten. Normally, only the message envelope
           sender and recipients are rewritten, the existence of this file
           causes the headers to be rewritten as well.

       warntime

           warntime specifies an amount of time in the same format as
           queuetime. If a message still has not been delivered after this
           period of time, the Courier mail server sends a warning message (a
           "delayed" Delivery Status Notification) to the sender. If warntime
           is missing, the Courier mail server sets warntime to four hours.

               Note
               The time interval specified by warntime is only approximate.
               The Courier mail server sends a delayed Delivery Status
               Notification at the conclusion of the first attempted delivery
               after warntime has elapsed.

   Webmail template files
       HTML output from the webmail server is generated from the template
       files in /usr/lib/courier/sqwebmail/html/en-us. It is possible to
       translate the webmail interface into another language simply by
       creating another subdirectory underneath
       /usr/lib/courier/sqwebmail/html, then meticulously translating each
       .html file. Each template file contains well-formed HTML, with dynamic
       content marked off by tags. Note that the large comment blocks in each
       HTML file need to be translated too, since they are inserted as dynamic
       content, elsewhere.

       The directory /usr/lib/courier/sqwebmail/html/en-us also contains
       several configuration files, in addition to the HTML template files.
       Doing so allows this configuration information to be defined for each
       available language.

       CHARSET
           This file consists of a single line of text, which names the
           character set used by the HTML template files. It is possible to
           specify multiple character set, by separating them with commas,
           provided that HTML templates use only the common portions of all
           listed character set.

           The default English HTML templates use strictly the "us-ascii"
           subset, and the CHARSET contains utf-8,iso-8859-1. When multiple
           character sets are listed, the first character set that's supported
           by the browser is picked, so with UTF-8 capable browsers the
           default webmail interface will use UTF-8, falling back to
           ISO-8859-1 for browsers that do not support UTF-8.

       footer
           The contents of this file, if it exists, are appended to all
           messages sent by the webmail server.

       ISPELLDICT
           This file consists of a single line of text, which contains the
           name of the dictionary used for spell-checking. It is passed as an
           argument to ispell, or aspell.

       LANGUAGE
           This file consists of a single line of text, which should always be
           the same as the name of its directory (en-us).

       LANGUAGE_PREF
           This file is not needed at runtime, its contents are used during
           installation. See webmail/html/README_LANG in the source
           distribution for more information.

       LOCALE
           The corresponding C locale for these templates.

       TIMEZONELIST
           This file lists the available timezones on the login screen. See
           the comments in this file for more information.

   Sender Policy Framework Keywords
       The Courier mail server can perform "Sender Policy Framework" checks on
       up to three addresses for each message. This is controlled by setting
       the following variables: BOFHSPFHELO, BOFHSPFMAILFROM, and BOFHSPFFROM.
       Each variable is set to a comma-separated list of the following
       keywords: "off" - SPF verification disabled (default); "none",
       "neutral", "pass", "fail", "softfail", "error", "unknown" - these
       keywords correspond to the possible results of an SPF check, the
       message is accepted for the listed SPF results only, any other SPF
       result is rejected; "all" - shorthand for all possible SPF results, use
       "all" to run SPF in informational mode only, recording the SPF status
       in the Received-SPF: header.

       A rejected SPF result gets kicked back with a permanent error
       indication if the SPF result is listed in BOFHSPFHARDERROR, and a
       temporary error indication otherwise.

       When enabling SPF checking, the keyword list should always include
       "pass" (it makes no sense to do otherwise) and "none". The keyword list
       should also include "softfail", "neutral", and "unknown". See the SPF
       draft for a description of these status results. At some distant
       future, the keyword list will only include "pass", rejecting all
       senders without a stated policy. This might be desirable at some point
       in the future, but not right now.

       The BOFHSPFFROM list may also include an additional keyword,
       "mailfromok".  BOFHSPFMAILFROM and BOFHSPFFROM are trade-offs. Using
       BOFHSPFMAILFROM is faster, and it does not require the entire message
       to be received, before running the SPF check.  BOFHSPFFROM checking can
       only occur after the entire message is received, but it's more
       reliable. If "mailfromok" is listed, the From: is not checked if the
       MAIL FROM command was checked with the "pass" result.

       In other words: the From: header is checked if MAIL FROM was empty, or
       did not pass the SPF checks. If MAIL FROM passed the SPF check the
       Courier mail server won't bother looking at the From: header.

           Note
           A conservative policy should not reject failed SPF checks from the
           From:header, because it can be counterproductive in some
           situations. This is because when a sender from a domain with a
           published SPF policy sends a message to a mailing list, the message
           goes through the mailing list processor's IP address, and it will
           fail the SPF check unless the domain SPF explicitly authorizes the
           mailing list processor's IP address.

           This is very unlikely. The end result is that domains with a
           published SPF record get punished, and domains without an SPF
           record get off scott free. Mailing lists should be encouraged to
           publish their own SPF records for mailing list traffic; then the
           "mailfromok" keyword can validate the mailing list's return
           address, and forego checking of the "From:" header from the mailing
           list, while still checking the "From:" header from everyone else.

           Another alternative is to use opt BOFHSPFFROM=all for advisory
           purposes only. Post-delivery mail filters can key off the
           "Received-SPF" header.

           Note
           The Courier mail server can add up to three "Received-SPF" headers
           of its own, one for each SPF check. The Courier mail server renames
           any existing "Received-SPF" header as "Old-Received-SPF". All
           "Received-SPF" headers delivered to a local mailbox will always
           come from the Courier mail server.

BUGS

       Flushing a single message will not work if the message queue is backed
       up. When that happens, your only available option is to flush the
       entire queue.

       courier start fails if the Courier mail server has detected a fatal
       operational error. In this situation the top-level courierd daemon
       sleeps for a minute, before automatically restarting. During this sleep
       interval courier stop does not work.

SEE ALSO

       cancelmsg(1)[13], maildirmake(1)[11], maildrop(1)[7], preline(1)[15],
       sendmail(1)[16], testmxlookup(1)[17], dot-courier(5)[5], authlib(7)[3],
       courierfax(8)[8], courierfilter(8)[6], filterctl(8)[6],
       courierldapaliasd(8)[10], courierpop3d(8)[18], courierpop3d(8)[18],
       couriertcpd(8)[19], courieruucp(8)[14], esmtpd(8)[20], imapd(8)[21],
       localmailfilter(7)[2], mailq(1)[1], makeacceptmailfor(8)[22],
       makealiases(8)[23], makehosteddomains(8)[9], makepercentrelay(8)[24],
       makesmtpaccess(8)[4], makeuserdb(8)[25], pw2userdb(8)[25],
       mkesmtpdcert(8)[26], mkimapdcert(8)[27], pop3d(8)[28], submit(8)[29],
       userdb(8)[30].

AUTHOR

       Sam Varshavchik
           Author

NOTES

        1. mailq(1)
           [set $man.base.url.for.relative.links]/mailq.html

        2. localmailfilter(7)
           [set $man.base.url.for.relative.links]/localmailfilter.html

        3. authlib(7)
           [set $man.base.url.for.relative.links]/authlib.html

        4. makesmtpaccess(8)
           [set $man.base.url.for.relative.links]/makesmtpaccess.html

        5. dot-courier(5)
           [set $man.base.url.for.relative.links]/dot-courier.html

        6.

           courierfilter(8)
           [set $man.base.url.for.relative.links]/courierfilter.html

        7.

           maildrop(1)
           [set $man.base.url.for.relative.links]/maildrop.html

        8. courierfax(8)
           [set $man.base.url.for.relative.links]/courierfax.html

        9. makehosteddomains(8)
           [set $man.base.url.for.relative.links]/makehosteddomains.html

       10. courierldapaliasd(8)
           [set $man.base.url.for.relative.links]/courierldapaliasd.html

       11. maildirmake(1)
           [set $man.base.url.for.relative.links]/maildirmake.html

       12. maildropfilter(6)
           [set $man.base.url.for.relative.links]/maildropfilter.html

       13. cancelmsg(1)
           [set $man.base.url.for.relative.links]/cancelmsg.html

       14. courieruucp(8)
           [set $man.base.url.for.relative.links]/courieruucp.html

       15.

           preline(1)
           [set $man.base.url.for.relative.links]/preline.html

       16.

           sendmail(1)
           [set $man.base.url.for.relative.links]/sendmail.html

       17.

           testmxlookup(1)
           [set $man.base.url.for.relative.links]/testmxlookup.html

       18.

           courierpop3d(8)
           [set $man.base.url.for.relative.links]/courierpop3d.html

       19.

           couriertcpd(8)
           [set $man.base.url.for.relative.links]/couriertcpd.html

       20.

           esmtpd(8)
           [set $man.base.url.for.relative.links]/esmtpd.html

       21.

           imapd(8)
           [set $man.base.url.for.relative.links]/imapd.html

       22.

           makeacceptmailfor(8)
           [set $man.base.url.for.relative.links]/makeacceptmailfor.html

       23.

           makealiases(8)
           [set $man.base.url.for.relative.links]/makealiases.html

       24.

           makepercentrelay(8)
           [set $man.base.url.for.relative.links]/makepercentrelay.html

       25.

           makeuserdb(8)
           [set $man.base.url.for.relative.links]/makeuserdb.html

       26.

           mkesmtpdcert(8)
           [set $man.base.url.for.relative.links]/mkesmtpdcert.html

       27.

           mkimapdcert(8)
           [set $man.base.url.for.relative.links]/mkimapdcert.html

       28.

           pop3d(8)
           [set $man.base.url.for.relative.links]/pop3d.html

       29.

           submit(8)
           [set $man.base.url.for.relative.links]/submit.html

       30.

           userdb(8)
           [set $man.base.url.for.relative.links]/userdb.html