TRANSPORT(5)                                   File Formats Manual                                   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 triv‐
       ial-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 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 decreas‐
              ing precedence, the nexthop destination  is  taken  from  relay_transport,  sender_dependent_relay‐
              host_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) com‐
       mand.  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 corre‐
       sponding 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 charac‐
              ter is a `#'.

       multi-line text
              A logical line starts with non-whitespace text. A line that starts with whitespace continues a log‐
              ical 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, pat‐
       terns 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 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 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-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  trans‐
       port 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
       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
       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 fol‐
       lowing 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.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, one may specify hostname: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  sym‐
       bolic 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 expres‐
       sions. 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 sum‐
       mary. 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  patterns  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
       Use "postconf readme_directory" or "postconf html_directory" to locate this information.
       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)