Postfix manual - transport(5)

    TRANSPORT(5)                                                      TRANSPORT(5)

    NAME
           transport - Postfix transport table format

    SYNOPSIS
           postmap /etc/postfix/transport

           postmap -q "string" /etc/postfix/transport

           postmap -q - /etc/postfix/transport <inputfile

    DESCRIPTION
           The   optional  transport(5)  table  specifies  a  mapping  from  email
           addresses to message delivery  transports  and  next-hop  destinations.
           Message  delivery  transports  such as local or smtp are defined in the
           master.cf file, and next-hop destinations are typically hosts or domain
           names. The table is searched by the trivial-rewrite(8) daemon.

           This  mapping overrides the default transport:nexthop selection that is
           built into Postfix:

           local_transport (default: local:$myhostname)
                  This is the default for final delivery to  domains  listed  with
                  mydestination,  and  for  [ipaddress]  destinations  that  match
                  $inet_interfaces or $proxy_interfaces. The default nexthop  des-
                  tination is the MTA hostname.

           virtual_transport (default: virtual:)
                  This  is  the  default for final delivery to domains listed with
                  virtual_mailbox_domains. The default nexthop destination is  the
                  recipient domain.

           relay_transport (default: relay:)
                  This  is  the default for remote delivery to domains listed with
                  relay_domains. In order of decreasing  precedence,  the  nexthop
                  destination   is   taken   from  relay_transport,  sender_depen-
                  dent_relayhost_maps, relayhost, or from the recipient domain.

           default_transport (default: smtp:)
                  This is the default for remote delivery to  other  destinations.
                  In  order  of  decreasing precedence, the nexthop destination is
                  taken       from        sender_dependent_default_transport_maps,
                  default_transport,  sender_dependent_relayhost_maps,  relayhost,
                  or from the recipient domain.

           Normally, the transport(5) table is  specified  as  a  text  file  that
           serves as input to the postmap(1) command.  The result, an indexed file
           in dbm or db format, is used for fast searching  by  the  mail  system.
           Execute  the  command  "postmap  /etc/postfix/transport"  to rebuild an
           indexed file after changing the corresponding transport table.

           When the table is provided via other means such as NIS,  LDAP  or  SQL,
           the same lookups are done as for ordinary indexed files.

           Alternatively,  the  table  can be provided as a regular-expression map
           where patterns are given as regular  expressions,  or  lookups  can  be
           directed  to TCP-based server. In those case, the lookups are done in a
           slightly different way as described  below  under  "REGULAR  EXPRESSION
           TABLES" or "TCP-BASED TABLES".

    CASE FOLDING
           The  search string is folded to lowercase before database lookup. As of
           Postfix 2.3, the search string is not case folded with  database  types
           such  as  regexp: or pcre: whose lookup fields can match both upper and
           lower case.

    TABLE FORMAT
           The input format for the postmap(1) command is as follows:

           pattern result
                  When pattern matches the recipient address or  domain,  use  the
                  corresponding result.

           blank lines and comments
                  Empty  lines and whitespace-only lines are ignored, as are lines
                  whose first non-whitespace character is a `#'.

           multi-line text
                  A logical line starts with  non-whitespace  text.  A  line  that
                  starts with whitespace continues a logical line.

           The pattern specifies an email address, a domain name, or a domain name
           hierarchy, as described in section "TABLE LOOKUP".

           The result is of the form transport:nexthop and specifies how or  where
           to deliver mail. This is described in section "RESULT FORMAT".

    TABLE SEARCH ORDER
           With  lookups  from  indexed files such as DB or DBM, or from networked
           tables such as NIS, LDAP or SQL, patterns are tried  in  the  order  as
           listed below:

           user+extension@domain transport:nexthop
                  Deliver mail for user+extension@domain through transport to nex-
                  thop.

           user@domain transport:nexthop
                  Deliver mail for user@domain through transport to nexthop.

           domain transport:nexthop
                  Deliver mail for domain through transport to nexthop.

           .domain transport:nexthop
                  Deliver mail for any subdomain of domain  through  transport  to
                  nexthop. This applies only when the string transport_maps is not
                  listed  in  the  parent_domain_matches_subdomains  configuration
                  setting.  Otherwise, a domain name matches itself and its subdo-
                  mains.

           * transport:nexthop
                  The special pattern * represents any address (i.e. it  functions
                  as  the  wild-card  pattern,  and is unique to Postfix transport
                  tables).

           Note   1:   the   null   recipient   address   is    looked    up    as
           $empty_address_recipient@$myhostname (default: mailer-daemon@hostname).

           Note 2: user@domain or user+extension@domain  lookup  is  available  in
           Postfix 2.0 and later.

    RESULT FORMAT
           The  lookup  result  is  of  the form transport:nexthop.  The transport
           field specifies a mail delivery transport such as smtp  or  local.  The
           nexthop field specifies where and how to deliver mail.

           The  transport  field  specifies  the name of a mail delivery transport
           (the first name of a mail delivery service entry in  the  Postfix  mas-
           ter.cf file).

           The  nexthop  field usually specifies one recipient domain or hostname.
           In the case of the Postfix SMTP/LMTP client, the nexthop field may con-
           tain  a  list  of nexthop destinations separated by comma or whitespace
           (Postfix 3.5 and later).

           The syntax of a nexthop destination is transport dependent.  With SMTP,
           specify a service on a non-default port as host:service, and disable MX
           (mail exchanger) DNS lookups with [host] or [host]:port. The [] form is
           required when you specify an IP address instead of a hostname.

           A  null transport and null nexthop field means "do not change": use the
           delivery transport and nexthop information that would be used when  the
           entire transport table did not exist.

           A non-null transport field with a null nexthop field resets the nexthop
           information to the recipient domain.

           A null transport field with non-null nexthop field does not modify  the
           transport information.

    EXAMPLES
           In  order  to  deliver internal mail directly, while using a mail relay
           for all other mail, specify a null entry for internal destinations  (do
           not change the delivery transport or the nexthop information) and spec-
           ify a wildcard for all other destinations.

                my.domain    :
                .my.domain   :
                *            smtp:outbound-relay.my.domain

           In order to send mail for example.com and its subdomains via  the  uucp
           transport to the UUCP host named example:

                example.com      uucp:example
                .example.com     uucp:example

           When  no nexthop host name is specified, the destination domain name is
           used instead. For example, the following directs  mail  for  user@exam-
           ple.com  via  the  slow  transport to a mail exchanger for example.com.
           The slow transport could be configured to  run  at  most  one  delivery
           process at a time:

                example.com      slow:

           When no transport is specified, Postfix uses the transport that matches
           the address domain class (see DESCRIPTION above).  The following  sends
           all  mail  for  example.com  and  its  subdomains to host gateway.exam-
           ple.com:

                example.com      :[gateway.example.com]
                .example.com     :[gateway.example.com]

           In the above example, the [] suppress MX lookups.  This  prevents  mail
           routing loops when your machine is primary MX host for example.com.

           In  the case of delivery via SMTP or LMTP, one may specify host:service
           instead of just a host:

                example.com      smtp:bar.example:2025

           This directs mail for user@example.com to host bar.example  port  2025.
           Instead  of  a  numerical  port a symbolic name may be used. Specify []
           around the hostname if MX lookups must be disabled.

           Deliveries via SMTP or LMTP support multiple destinations  (Postfix  >=
           3.5):

                example.com      smtp:bar.example, foo.example

           This  tries  to  deliver  to  bar.example  before  trying to deliver to
           foo.example.

           The error mailer can be used to bounce mail:

                .example.com     error:mail for *.example.com is not deliverable

           This causes all mail for user@anything.example.com to be bounced.

    REGULAR EXPRESSION TABLES
           This section describes how the table lookups change when the  table  is
           given  in the form of regular expressions. For a description of regular
           expression lookup table syntax, see regexp_table(5) or pcre_table(5).

           Each pattern is a regular expression that  is  applied  to  the  entire
           address  being  looked up. Thus, some.domain.hierarchy is not looked up
           via  its  parent  domains,  nor  is  user+foo@domain   looked   up   as
           user@domain.

           Patterns  are  applied  in the order as specified in the table, until a
           pattern is found that matches the search string.

           The trivial-rewrite(8) server disallows regular expression substitution
           of $1 etc. in regular expression lookup tables, because that could open
           a security hole (Postfix version 2.3 and later).

    TCP-BASED TABLES
           This section describes how the table lookups change  when  lookups  are
           directed   to  a  TCP-based  server.  For  a  description  of  the  TCP
           client/server lookup protocol, see tcp_table(5).  This feature  is  not
           available up to and including Postfix version 2.4.

           Each  lookup  operation  uses the entire recipient address once.  Thus,
           some.domain.hierarchy is not looked up via its parent domains,  nor  is
           user+foo@domain looked up as user@domain.

           Results are the same as with indexed file lookups.

    CONFIGURATION PARAMETERS
           The  following  main.cf  parameters  are especially relevant.  The text
           below provides only a  parameter  summary.  See  postconf(5)  for  more
           details including examples.

           empty_address_recipient (MAILER-DAEMON)
                  The recipient of mail addressed to the null address.

           parent_domain_matches_subdomains (see 'postconf -d' output)
                  A  list of Postfix features where the pattern "example.com" also
                  matches subdomains  of  example.com,  instead  of  requiring  an
                  explicit ".example.com" pattern.

           transport_maps (empty)
                  Optional  lookup  tables with mappings from recipient address to
                  (message delivery transport, next-hop destination).

    SEE ALSO
           trivial-rewrite(8), rewrite and resolve addresses
           master(5), master.cf file format
           postconf(5), configuration parameters
           postmap(1), Postfix lookup table manager

    README FILES
           ADDRESS_REWRITING_README, address rewriting guide
           DATABASE_README, Postfix lookup table overview
           FILTER_README, external content filter

    LICENSE
           The Secure Mailer license must be distributed with this software.

    AUTHOR(S)
           Wietse Venema
           IBM T.J. Watson Research
           P.O. Box 704
           Yorktown Heights, NY 10598, USA

           Wietse Venema
           Google, Inc.
           111 8th Avenue
           New York, NY 10011, USA

                                                                      TRANSPORT(5)