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] des‐
              tinations    that    match    $inet_interfaces   or
              $proxy_interfaces. The default nexthop  destination
              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_dependent_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_depen
              dent_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 expres‐
       sions,  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 logi‐
              cal 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 nexthop.

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

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

       .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 par
              ent_domain_matches_subdomains  configuration   set‐
              ting.   Otherwise, a domain name matches itself and
              its subdomains.

       * 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-dae‐
       mon@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 master.cf file).

       The interpretation  of  the  nexthop  field  is  transport
       dependent.  In  the  case  of 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 result means "do not
       change": use the delivery transport and  nexthop  informa‐
       tion  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  trans‐
       port  or  the  nexthop information) and specify 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@example.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.example.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, one may specify host
       name: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.

       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  ta‐
       ble,  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 descrip‐
       tion of the TCP client/server lookup protocol, see tcp_ta
       ble(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
              The address that is looked up instead of  the  null
              sender address.

       parent_domain_matches_subdomains
              List  of  Postfix features that use domain.tld pat‐
              terns  to  match  sub.domain.tld  (as  opposed   to
              requiring .domain.tld patterns).

       transport_maps
              List of transport lookup tables.

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

                                                                  TRANSPORT(5)