Provided by: opensmtpd_6.8.0p2-4build1_amd64 bug

NAME

     smtpd.conf — Simple Mail Transfer Protocol daemon configuration file

DESCRIPTION

     smtpd.conf is the configuration file for the mail daemon smtpd(8).

     When mail arrives, each “RCPT TO:” command generates a mail envelope.  If an envelope
     matches any of a pre-designated set of criteria (using the match directive), the message is
     accepted for delivery.  A copy of the message, as well as its associated envelopes, is saved
     in the mail queue and later dispatched according to an associated set of actions (using the
     action directive).  If an envelope does not match any options, it is rejected.  The match
     rules are evaluated sequentially, with the first match winning.

     The format of the configuration file is fairly flexible.  The current line can be extended
     over multiple lines using a backslash (‘\’).  Comments can be put anywhere in the file using
     a hash mark (‘#’), and extend to the end of the current line.  Care should be taken when
     commenting out multi-line text: the comment is effective until the end of the entire block.
     Argument names not beginning with a letter, digit, or underscore, as well as reserved words
     (such as listen, match, and port), must be quoted.  Arguments containing whitespace should
     be surrounded by double quotes (").

     Macros can be defined that are later expanded in context.  Macro names must start with a
     letter, digit, or underscore, and may contain any of those characters, but may not be
     reserved words.  Macros are not expanded inside quotes.  For example:

           lan_addr = "192.168.0.1"
           listen on $lan_addr
           listen on $lan_addr tls auth

     The syntax of smtpd.conf is described below.

     action name method [options]
             When the queue runner processes an envelope from the mail queue, it carries out the
             action name, selected by the match ... action directive when the message was
             received.  The action directive provides configuration data for delivery attempts.
             Required lookups are performed at the time of each delivery attempt.  Consequently,
             changing an action directive or the files it references and restarting the smtpd(8)
             daemon causes the changes to take effect for subsequent delivery attempts for the
             respective dispatcher name, even for messages that were already stuck in the queue
             prior to the configuration changes.

             The delivery method parameter may be one of the following:

             expand-only
                     Only accept the message if a delivery method was specified in an aliases or
                     .forward file.

             forward-only
                     Only accept the message if the recipient results in a remote address after
                     the processing of aliases or forward file.

             lmtp destination [rcpt-to]
                     Deliver the message to an LMTP server at destination.  The location may be
                     expressed as host:port or as a UNIX socket.

                     Optionally, rcpt-to might be specified to use the recipient email address
                     (after expansion) instead of the local user in the LMTP session as RCPT TO.

             maildir [pathname [junk]]
                     Deliver the message to the maildir in pathname if specified, or by default
                     to ~/Maildir.

                     The pathname may contain format specifiers that are expanded before use (see
                     FORMAT SPECIFIERS).

                     If the junk argument is provided, the message will be moved to the ‘Junk’
                     folder if it contains a positive ‘X-Spam’ header.  This folder will be
                     created under pathname if it does not yet exist.

             mbox    Deliver the message to the user's mbox with mail.local(8).

             mda command
                     Delegate the delivery to a command that receives the message on its standard
                     input.

                     The command may contain format specifiers that are expanded before use (see
                     FORMAT SPECIFIERS).

             relay   Relay the message to another SMTP server.

             The local delivery methods support additional options:

             alias <table>
                     Use the mapping table for aliases(5) expansion.

             ttl n{s|m|h|d}
                     Specify how long a message may remain in the queue.

             user username
                     Specify the username for performing the delivery, to be looked up with
                     getpwnam(3).

                     This is used for virtual hosting where a single username is in charge of
                     handling delivery for all virtual users.

                     This option is not usable with the mbox delivery method.

             userbase <table>
                     Use the mapping table for user lookups instead of the getpwnam(3) function.

                     The userbase does not apply for the user option.

             virtual <table>
                     Use the mapping table for virtual expansion.  The aliasing table format is
                     described in table(5).

             wrapper name
                     Use the wrapper specified in mda wrapper.

             The relay delivery methods also support additional options:

             backup  Operate as a backup mail exchanger delivering messages to any mail exchanger
                     with higher priority.

             backup mx name
                     Operate as a backup mail exchanger delivering messages to any mail exchanger
                     with higher priority than mail exchanger identified as name.

             helo heloname
                     Advertise heloname as the hostname to other mail exchangers during the HELO
                     phase.

             helo-src <table>
                     Use the mapping table to look up a hostname matching the source address, to
                     advertise during the HELO phase.

             domain <domains>
                     Do not perform MX lookups but look up destination domain in domains and use
                     matching relay url as relay host.

             host relay-url
                     Do not perform MX lookups but relay messages to the relay host described by
                     relay-url.  The format for relay-url is [proto://[label@]]host[:port].  The
                     following protocols are available:

                     smtp        Normal SMTP session with opportunistic STARTTLS (the default).
                     smtp+tls    Normal SMTP session with mandatory STARTTLS.
                     smtp+notls  Plain text SMTP session without TLS.
                     lmtp        LMTP session.  port is required.
                     smtps       SMTP session with forced TLS on connection, default port is 465.
                     Unless noted, port defaults to 25.

                     The label corresponds to an entry in a credentials table, as documented in
                     table(5).  It is used with the “smtp+tls” and “smtps” protocols for
                     authentication.  Server certificates for those protocols are verified by
                     default.

             pki pkiname
                     For secure connections, use the certificate associated with pkiname
                     (declared in a pki directive) to prove the client's identity to the remote
                     mail server.

             srs     When relaying a mail resulting from a forward, use the Sender Rewriting
                     Scheme to rewrite sender address.

             tls [no-verify]
                     Require TLS to be used when relaying, using mandatory STARTTLS by default.
                     When used with a smarthost, the protocol must not be “smtp+notls://”.  If
                     no-verify is specified, do not require a valid certificate.

             auth <table>
                     Use the mapping table for connecting to relay-url using credentials.  This
                     option is usable only with host option.  The credential table format is
                     described in table(5).

             mail-from mailaddr
                     Use mailaddr as the MAIL FROM address within the SMTP transaction.

             src sourceaddr | <sourceaddr>
                     Use the string or list table sourceaddr for the source IP address, which is
                     useful on machines with multiple interfaces.  If the list contains more than
                     one address, all of them are used in such a way that traffic is routed as
                     efficiently as possible.

     admd authservid
             The Administrative Management Domain this mailserver belongs to.  The authservid
             will be forwarded to filters using it to identify or mark authentication-results
             headers.  If omitted it defaults to the server name.

     bounce warn-interval delay [, delay ...]
             Send warning messages to the envelope sender when temporary delivery failures cause
             a message to remain on the queue for longer than delay.  Each delay parameter
             consists of a positive decimal integer and a unit s, m, h, or d.  At most four delay
             parameters can be specified.  The default is "bounce warn-interval 4h", sending a
             single warning after four hours.

     ca caname cert cafile
             Associate the Certificate Authority (CA) certificate file cafile with host caname,
             and use that file as the CA certificate for that host.  caname is the server's name,
             derived from the default hostname or set using either /etc/mailname or using the
             hostname directive.

     filter chain-name chain {filter-name [, ...]}
             Register a chain of filters chain-name, consisting of the filters listed from
             filter-name.  Filters part of a filter chain are executed in order of declaration
             for each phase that they are registered for.  A filter chain may be used in place of
             a filter for any directive but filter chains themselves.

     filter filter-name phase phase-name match conditions decision
             Register a filter filter-name.  A decision about what to do with the mail is taken
             at phase phase-name when matching conditions.  Phases, matching conditions, and
             decisions are described in MAIL FILTERING, below.

     filter filter-name proc proc-name
             Register "proc" filter filter-name backed by the proc-name process.

     filter filter-name proc-exec command
             Register and execute "proc" filter filter-name from command.  If command starts with
             a slash it is executed with an absolute path, else it will be run from
             “/usr/libexec/opensmtpd”.

     include "pathname"
             Replace this directive with the content of the additional configuration file at the
             absolute pathname.

     listen on interface [family] [options]
             Listen on the interface for incoming connections, using the same syntax as for
             ifconfig(8).  The interface parameter may also be an interface group, an IP address,
             or a domain name.  Listening can optionally be restricted to a specific address
             family, which can be either inet4 or inet6.

             The options are as follows:

             auth [<authtable>]
                     Support SMTPAUTH: clients may only start SMTP transactions after successful
                     authentication.  Users are authenticated against either their own normal
                     login credentials or a credentials table authtable, the format of which is
                     described in table(5).

             auth-optional [<authtable>]
                     Support SMTPAUTH optionally: clients need not authenticate, but may do so.
                     This allows a listen on directive to both accept incoming mail from
                     untrusted senders and permit outgoing mail from authenticated users (using
                     match auth).  It can be used in situations where it is not possible to
                     listen on a separate port (usually the submission port, 587) for users to
                     authenticate.

             ca caname
                     For secure connections, use the CA certificate associated with caname
                     (declared in a ca directive) as the CA certificate when verifying client
                     certificates.

             filter name
                     Apply filter name on connections handled by this listener.

             hostname hostname
                     Use hostname in the greeting banner instead of the default server name.

             hostnames <names>
                     Override the server name for specific addresses.  The names table contains a
                     mapping of IP addresses to hostnames.  If the address on which the
                     connection arrives appears in the mapping, the associated hostname is used.

             mask-src
                     Omit the from part when prepending “Received” headers.

             no-dsn  Disable the DSN (Delivery Status Notification) extension.

             pki pkiname
                     For secure connections, use the certificate associated with pkiname
                     (declared in a pki directive) to prove a mail server's identity.

             port [port]
                     Listen on the given port instead of the default port 25.

             proxy-v2
                     Support the PROXYv2 protocol, rewriting appropriately source address
                     received from proxy.

             received-auth
                     In “Received” headers, report whether the session was authenticated and by
                     which local user.

             senders <users> [masquerade]
                     Look up the authenticated user in the users mapping table to find the email
                     addresses that user is allowed to submit mail as.  In addition, if the
                     masquerade option is provided, the From header is rewritten to match the
                     sender provided in the SMTP session.

             smtps   Support SMTPS, by default on port 465.  Mutually exclusive with tls.

             tag tag
                     Clients connecting to the listener are tagged with the given tag.

             tls     Support STARTTLS, by default on port 25.  Mutually exclusive with smtps.

             tls-require [verify]
                     Like tls, but force clients to establish a secure connection before being
                     allowed to start an SMTP transaction.  With the verify option, clients must
                     also provide a valid certificate to establish an SMTP session.

     listen on socket [options]
             Listen for incoming SMTP connections on the Unix domain socket /var/run/smtpd.sock.
             This is done by default, even if the directive is absent.

             The options are as follows:

             filter name
                     Apply filter name on connections handled by this listener.

             mask-src
                     Omit the from part when prepending “Received” headers.

             tag tag
                     Clients connecting to the listener are tagged with the given tag.

     match options action name
             If at least one mail envelope matches the options of one match action directive,
             receive the incoming message, put a copy into each matching envelope, and atomically
             save the envelopes to the mail spool for later processing by the respective
             dispatcher name.

             The following matching options are supported and can all be negated:

             [!] for any
                     Specify that session may address any destination.

             [!] for local
                     Specify that session may address any local domain.  This is the default, and
                     may be omitted.

             [!] for domain domain | <domain>
                     Specify that session may address the string or list table domain.

             [!] for domain regex domain | <domain>
                     Specify that session may address the regex or regex table domain.

             [!] for rcpt-to recipient | <recipient>
                     Specify that session may address the string or list table recipient.

             [!] for rcpt-to regex recipient | <recipient>
                     Specify that session may address the regex or regex table recipient.

             [!] from any
                     Specify that session may originate from any source.

             [!] from auth
                     Specify that session may originate from any authenticated user, no matter
                     the source IP address.

             [!] from auth user | <user>
                     Specify that session may originate from authenticated user or user list
                     user, no matter the source IP address.

             [!] from auth regex user | <user>
                     Specify that session may originate from authenticated regex or regex list
                     user, no matter the source IP address.

             [!] from local
                     Specify that session may only originate from a local IP address, or from the
                     local enqueuer.  This is the default, and may be omitted.

             [!] from mail-from sender | <sender>
                     Specify that session may originate from sender or sender list sender, no
                     matter the source IP address.

             [!] from mail-from regex sender | <sender>
                     Specify that session may originate from regex or regex list sender, no
                     matter the source IP address.

             [!] from rdns
                     Specify that session may only originate from an IP address that resolves to
                     a reverse DNS.

             [!] from rdns hostname | <hostname>
                     Specify that session may only originate from an IP address that resolves to
                     a reverse DNS matching string or list string hostname.

             [!] from rdns regex hostname | <hostname>
                     Specify that session may only originate from an IP address that resolves to
                     a reverse DNS matching regex or list regex hostname.

             [!] from socket
                     Specify that session may only originate from the local enqueuer.

             [!] from src address | <address>
                     Specify that session may only originate from string or list table address
                     which can be a specific address or a subnet expressed in CIDR-notation.

             [!] from src regex address | <address>
                     Specify that session may only originate from regex or regex table address
                     which can be a specific address or a subnet expressed in CIDR-notation.

             In addition, the following transaction options:

             [!] auth
                     Matches transactions which have been authenticated.

             [!] auth username | <username>
                     Matches transactions which have been authenticated for user or user list
                     username.

             [!] auth regex username | <username>
                     Matches transactions which have been authenticated for regex or regex list
                     username.

             [!] helo helo-name | <helo-name>
                     Specify that session's HELO / EHLO should match the string or list table
                     helo-name.

             [!] helo regex helo-name | <helo-name>
                     Specify that session's HELO / EHLO should match the regex or regex table
                     helo-name.

             [!] mail-from sender | <sender>
                     Specify that transactions's MAIL FROM should match the string or list table
                     sender.

             [!] mail-from regex sender | <sender>
                     Specify that transactions's MAIL FROM should match the regex or regex table
                     sender.

             [!] rcpt-to recipient | <recipient>
                     Specify that transaction's RCPT TO should match the string or list table
                     recipient.

             [!] rcpt-to regex recipient | <recipient>
                     Specify that transaction's RCPT TO should match the regex or regex table
                     recipient.

             [!] tag tag
                     Matches transactions tagged with the given tag.

             [!] tag regex tag
                     Matches transactions tagged with the given tag regex.

             [!] tls
                     Specify that transaction should take place in a TLS channel.

     match options reject
             Reject the incoming message during the SMTP dialogue.  The same options are
             supported as for the match action directive.

     mda wrapper name command
             Associate command with the mail delivery agent wrapper named name.  When a local
             delivery specifies a wrapper, the command associated with the wrapper will be
             executed instead.  The command may contain format specifiers (see FORMAT
             SPECIFIERS).

     mta max-deferred number
             When delivery to a given host is suspended due to temporary failures, cache at most
             number envelopes for that host such that they can be delivered as soon as another
             delivery succeeds to that host.  The default is 100.

     pki pkiname cert certfile
             Associate certificate file certfile with host pkiname, and use that file to prove
             the identity of the mail server to clients.  pkiname is the server's name, derived
             from the default hostname or set using either /etc/mailname or using the hostname
             directive.  If a fallback certificate or SNI is wanted, the ‘*’ wildcard may be used
             as pkiname.

             A certificate chain may be created by appending one or many certificates, including
             a Certificate Authority certificate, to certfile.  The creation of certificates is
             documented in starttls(8).

     pki pkiname key keyfile
             Associate the key located in keyfile with host pkiname.

     pki pkiname dhe params
             Specify the DHE parameters to use for DHE cipher suites with host pkiname.  Valid
             parameter values are none, legacy, and auto.  For legacy, a fixed key length of 1024
             bits is used, whereas for auto, the key length is determined automatically.  The
             default is none, which disables DHE cipher suites.

     proc proc-name command
             Register an external process named proc-name from command.  Such processes may be
             used to share the same instance between multiple filters.  If command starts with a
             slash it is executed with an absolute path, else it will be run from
             “/usr/libexec/opensmtpd”.

     queue compression
             Store queue files in a compressed format.  This may be useful to save disk space.

     queue encryption [key]
             Encrypt queue files with EVP_aes_256_gcm(3).  If no key is specified, it is read
             with getpass(3).  If the string stdin or a single dash (‘-’) is given instead of a
             key, the key is read from the standard input.

     queue ttl delay
             Set the default expiration time for temporarily undeliverable messages, given as a
             positive decimal integer followed by a unit s, m, h, or d.  The default is four days
             (4d).

     smtp ciphers control
             Set the control string for SSL_CTX_set_cipher_list(3).  The default is
             "HIGH:!aNULL:!MD5".

     smtp limit max-mails count
             Limit the number of messages to count for each session.  The default is 100.

     smtp limit max-rcpt count
             Limit the number of recipients to count for each transaction.  The default is 1000.

     smtp max-message-size size
             Reject messages larger than size, given as a positive number of bytes or as a string
             to be parsed with scan_scaled(3).  The default is "35M".

     smtp sub-addr-delim character
             When resolving the local part of a local email address, ignore the ASCII character
             and all characters following it.  The default is ‘+’.

     srs key secret
             Set the secret key to use for SRS, the Sender Rewriting Scheme.

     srs key backup secret
             Set a backup secret key to use as a fallback for SRS.  This can be used to implement
             SRS key rotation.

     srs ttl delay
             Set the time-to-live delay for SRS envelopes.  After this delay, a bounce reply to
             the SRS address will be discarded to limit risks of forged addresses.  The default
             is four days (4d).

     table name [type:]pathname
             Tables provide additional configuration information for smtpd(8) in the form of
             lists or key-value mappings.  The format of the entries depends on what the table is
             used for.  Refer to table(5) for the exhaustive documentation.

             Each table is identified by an arbitrary, unique name.

             If the type is db, information is stored in a file created with makemap(8); if it is
             file or omitted, information is stored in a plain text file using the format
             described in table(5).  The pathname to the file must be absolute.

     table name {value [, ...]}
             Instead of using a separate file, declare a list table containing the given static
             values.  The table must contain at least one value and may declare multiple values
             as a comma-separated (whitespace optional) list.

     table name {key=value [, ...]}
             Instead of using a separate file, declare a mapping table containing the given
             static key-value pairs.  The table must contain at least one key-value pair and may
             declare multiple pairs as a comma-separated (whitespace optional) list.

   MAIL FILTERING
     In a regular workflow, smtpd(8) may accept or reject a message based only on the content of
     envelopes.  Its decisions are about the handling of the message, not about the handling of
     an active session.

     Filtering extends the decision making process by allowing smtpd(8) to stop at each phase of
     an SMTP session, check that conditions are met, then decide if a session is allowed to move
     forward.

     With filtering, a session may be interrupted at any phase before an envelope is complete.  A
     message may also be rejected after being submitted, regardless of whether the envelope was
     accepted or not.

     The following phases are currently supported:

           connect      upon connection, before a banner is displayed
           helo         after HELO command is submitted
           ehlo         after EHLO command is submitted
           mail-from    after MAIL FROM command is submitted
           rcpt-to      after RCPT TO command is submitted
           data         after DATA command is submitted
           commit       after message is fully is submitted

     At each phase, various conditions may be matched.  The fcrdns, rdns, and src data are
     available in all phases, but other data must have been already submitted before they are
     available.

           fcrdns                   forward-confirmed reverse DNS is valid
           rdns                     session has a reverse DNS
           rdns <table>             session has a reverse DNS in table
           src <table>              source address is in table
           helo <table>             helo name is in table
           auth                     session is authenticated
           auth <table>             session username is in table
           mail-from <table>        sender address is in table
           rcpt-to <table>          recipient address is in table

     These conditions may all be negated by prefixing them with an exclamation mark:

           !fcrdns                  forward-confirmed reverse DNS is invalid

     Any conditions using a table may indicate that tables hold regex by prefixing the table name
     with the keyword regex.

           helo regex <table>       helo name matches a regex in table

     Finally, a number of decisions may be taken:

           bypass                   the session or transaction bypasses filters
           disconnect message       the session is disconnected with message
           junk                     the session or transaction is junked, i.e., an ‘X-Spam: yes’
                                    header is added to any messages
           reject message           the command is rejected with message
           rewrite value            the command parameter is rewritten with value

     Decisions that involve a message require that the message be RFC valid, meaning that they
     should either start with a 4xx or 5xx status code.  Descisions can be taken at any phase,
     though junking can only happen before a message is committed.

   FORMAT SPECIFIERS
     Some configuration directives support expansion of their parameters at runtime.  Such
     directives (for example action maildir, action mda) may use format specifiers which are
     expanded before delivery or relaying.  The following formats are currently supported:

           %{sender}            sender email address, may be empty string
           %{sender.user}       user part of the sender email address, may be empty
           %{sender.domain}     domain part of the sender email address, may be empty
           %{rcpt}              recipient email address
           %{rcpt.user}         user part of the recipient email address
           %{rcpt.domain}       domain part of the recipient email address
           %{dest}              recipient email address after expansion
           %{dest.user}         user part after expansion
           %{dest.domain}       domain part after expansion
           %{user.username}     local user
           %{user.directory}    home directory of the local user
           %{mbox.from}         name used in mbox From separator lines
           %{mda}               mda command, only available for mda wrappers

     Expansion formats also support partial expansion using the optional bracket notations with
     substring offset.  For example, with recipient domain “example.org”:

           %{rcpt.domain[0]}       expands to “e”
           %{rcpt.domain[1]}       expands to “x”
           %{rcpt.domain[8:]}      expands to “org”
           %{rcpt.domain[-3:]}     expands to “org”
           %{rcpt.domain[0:6]}     expands to “example”
           %{rcpt.domain[0:-4]}    expands to “example”

     In addition, modifiers may be applied to the token.  For example, with recipient
     “User+Tag@Example.org”:

           %{rcpt:lowercase}          expands to “user+tag@example.org”
           %{rcpt:uppercase}          expands to “USER+TAG@EXAMPLE.ORG”
           %{rcpt:strip}              expands to “User@Example.org”
           %{rcpt:lowercase|strip}    expands to “user@example.org”

     For security concerns, expanded values are sanitized and potentially dangerous characters
     are replaced with ‘:’.  In situations where they are desirable, the “raw” modifier may be
     applied.  For example, with recipient “user+t?g@example.org”:

           %{rcpt}        expands to “user+t:g@example.org”
           %{rcpt:raw}    expands to “user+t?g@example.org

FILES

     /etc/smtpd.conf     Default smtpd(8) configuration file.
     /etc/mailname       If this file exists, the first line is used as the server name.
                         Otherwise, the server name is derived from the local hostname returned
                         by gethostname(3), either directly if it is a fully qualified domain
                         name, or by retrieving the associated canonical name through
                         getaddrinfo(3).
     /var/run/smtpd.sock
                         Unix domain socket for incoming SMTP connections.
     /var/spool/smtpd/   Spool directories for mail during processing.

EXAMPLES

     The default smtpd.conf file which ships with OpenBSD listens on the loopback network
     interface (lo0) and allows for mail from users and daemons on the local machine, as well as
     permitting email to remote servers.  Some more complex configurations are given below.

     This first example is the same as the default configuration, but all outgoing mail is
     forwarded to a remote SMTP server.  A secrets file is needed to specify a username and
     password:

           # touch /etc/secrets
           # chmod 640 /etc/secrets
           # chown root:_smtpd /etc/secrets
           # echo "bob username:password" > /etc/secrets

     smtpd.conf would look like this:

           table aliases file:/etc/aliases
           table secrets file:/etc/secrets

           listen on lo0

           action "local_mail" mbox alias <aliases>
           action "outbound" relay host smtp+tls://bob@smtp.example.com \
                   auth <secrets>

           match from local for local action "local_mail"
           match from local for any action "outbound"

     In this second example, the aim is to permit mail delivery and relaying only for users that
     can authenticate (using their normal login credentials).  An RSA certificate must be
     provided to prove the server's identity.  The mail server listens on all interfaces the
     default routes point to.  Mail with a local destination is sent to an external MDA.  First,
     the RSA certificate is created:

           # openssl genrsa -out /etc/ssl/private/mail.example.com.key 4096
           # openssl req -new -x509 -key /etc/ssl/private/mail.example.com.key \
                   -out /etc/ssl/mail.example.com.crt -days 365
           # chmod 600 /etc/ssl/mail.example.com.crt
           # chmod 600 /etc/ssl/private/mail.example.com.key

     In the example above, a certificate valid for one year was created.  The configuration file
     would look like this:

           pki mail.example.com cert "/etc/ssl/mail.example.com.crt"
           pki mail.example.com key "/etc/ssl/private/mail.example.com.key"

           table aliases file:/etc/aliases

           listen on lo0
           listen on egress tls pki mail.example.com auth

           action mda_with_aliases mda "/path/to/mda -f -" alias <aliases>
           action mda_without_aliases mda "/path/to/mda -f -"
           action "outbound" relay

           match for local action mda_with_aliases
           match from any for domain example.com action mda_without_aliases
           match for any action "outbound"
           match auth from any for any action "outbound"

     For sites that wish to sign messages using DKIM, the following example uses
     opensmtpd-filter-dkimsign for DKIM signing:

           table aliases file:/etc/aliases

           filter "dkimsign" proc-exec "filter-dkimsign -d <domain> -s <selector> \
                   -k /etc/dkim/private.key" user _dkimsign group _dkimsign

           listen on socket filter "dkimsign"
           listen on lo0 filter "dkimsign"

           action "local_mail" mbox alias <aliases>
           action "outbound" relay

           match for local action "local_mail"
           match for any action "outbound"

     Alternatively, the opensmtpd-filter-rspamd package may be used to provide integration with
     rspamd, a third-party daemon which provides multiple antispam features as well as DKIM
     signing.  As well as configuring rspamd itself, it requires use of the proc-exec keyword:

           filter "rspamd" proc-exec "filter-rspamd"

     Sites that accept non-local messages may be able to cut down on the volume of spam received
     by rejecting forged messages that claim to be from the local domain.  The following example
     uses a list table other-relays to specify the IP addresses of relays that may legitimately
     originate mail with the owner's domain as the sender.

           table aliases file:/etc/aliases
           table other-relays file:/etc/other-relays

           listen on lo0
           listen on egress

           action "local_mail" mbox alias <aliases>
           action "outbound" relay

           match for local action "local_mail"
           match for any action "outbound"
           match !from src <other-relays> mail-from "@example.com" for any \
                 reject
           match from any for domain example.com action "local_mail"

SEE ALSO

     mailer.conf(5), table(5), makemap(8), smtpd(8)

HISTORY

     smtpd(8) first appeared in OpenBSD 4.6.