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.

           * 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)