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] 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
                  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.

           Note 1: the special pattern * represents any address (i.e.
           it functions as the wild-card pattern).

           Note  2:  the  null  recipient  address  is  looked  up as
           $empty_address_recipient@$myhostname (default: mailer-dae-
           mon@hostname).

           Note  3:  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
           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)