transport (5)

Contents

NAME
SYNOPSIS
DESCRIPTION
CASE FOLDING
TABLE FORMAT
TABLE SEARCH ORDER
RESULT FORMAT
EXAMPLES
REGULAR EXPRESSION TABLES
TCP-BASED TABLES
CONFIGURATION PARAMETERS
SEE ALSO
README FILES
LICENSE
AUTHOR(S)

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_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".

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 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".


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_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 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.


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 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.


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 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 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 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