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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 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 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_dependent_default_trans‐‐
              port_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 TA‐
       BLES" 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-white‐
              space 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 de‐
       scribed in section "TABLE SEARCH ORDER".

       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 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_subdo‐‐
              mains 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 pat‐
              tern, and is unique to Postfix transport tables).

       Note 1: the null recipient address is looked up as $empty_address_recipient@$myhostname  (de‐
       fault: 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 de‐
       livery 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 nexthop field usually specifies one recipient domain or hostname.  In  the  case  of  the
       Postfix  SMTP/LMTP client, the nexthop field may contain a list of nexthop destinations sepa‐
       rated 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 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 ex‐
       ample, the following directs mail for user@example.com via the slow transport to a  mail  ex‐
       changer  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 subdo‐
       mains 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 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 dis‐
       abled.

       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 reg‐‐
       exp_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 pa‐
       rameter 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
       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)