DOKK / manpages / debian 10 / postfix / transport.5.en
TRANSPORT(5) File Formats Manual TRANSPORT(5)

transport - Postfix transport table format

postmap /etc/postfix/transport
postmap -q "string" /etc/postfix/transport
postmap -q - /etc/postfix/transport <inputfile


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:

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.
This is the default for final delivery to domains listed with virtual_mailbox_domains. The default nexthop destination is the recipient domain.
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.
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) 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 TABLES" or "TCP-BASED TABLES".



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.










The input format for the postmap(1) command is as
  follows:



  

  
When pattern matches the recipient address or domain, use the
      corresponding result.

  

  
Empty lines and whitespace-only lines are ignored, as are lines whose
      first non-whitespace character is a `#'.

  

  
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 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".










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:



  

  
Deliver mail for user+extension@domain through transport to
      nexthop.

  

  
Deliver mail for user@domain through transport to
      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.










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
    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.










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 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
    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 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.










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 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).










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.










The following main.cf parameters are especially relevant.
    The text below provides only a parameter summary. See postconf(5) for
    more details including examples.



  

  
The address that is looked up instead of the null sender address.

  

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

  

  
List of transport lookup tables.










trivial-rewrite(8), rewrite and resolve addresses
master(5), master.cf file format
postconf(5), configuration parameters
postmap(1), Postfix lookup table manager










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










The Secure Mailer license must be distributed with this
  software.








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