TRANSPORT(5) File Formats Manual TRANSPORT(5)
transport - format of Postfix transport table
postmap -q "string" /etc/postfix/transport
postmap -q - /etc/postfix/transport <<inputfile
The optional transport table specifies a mapping from email addresses
to message delivery transports and/or relay hosts. The mapping is used
by the trivial-rewrite(8) daemon.
This mapping overrides the default routing that is built into Postfix:
A list of domains that is by default delivered via $local_trans-
A list of domains that is by default delivered via $vir-
A list of domains that is by default delivered via $relay_trans-
any other destination
Mail for any other destination is by default delivered via
Normally, the transport 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 in order to rebuild the
indexed file after changing the 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. In that case, the
lookups are done in a slightly different way as described in section
"REGULAR EXPRESSION TABLES".
The input format for the postmap(1) command is as follows:
When pattern matches the recipient address or domain, use the
blank lines and comments
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. The transport field spec-
ifies a mail delivery transport such as smtp or local. The nexthop
field specifies where and how to deliver mail. More details are given
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
Mail for user+extension@domain is delivered through transport to
Mail for user@domain is delivered through transport to nexthop.
Mail for domain is delivered through transport to nexthop.
Mail for any subdomain of domain is delivered 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 subdo-
Note 1: the special pattern * represents any address (i.e. it functions
as the wild-card pattern).
Note 2: the null recipient address is looked up as
$empty_address_recipient@$myhostname (default: mailer-daemon@hostname).
The transport field specifies the name of a mail delivery transport
(the first name of a mail delivery service entry in the Postfix mas-
The interpretation of the nexthop field is transport dependent. In the
case of SMTP, specify host:service for a non-default server port, and
use [host] or [host]:port in order to disable MX (mail exchanger) DNS
lookups. 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
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 spec-
ify a wildcard for all other destinations.
In order to send mail for foo.org and its subdomains via the uucp
transport to the UUCP host named foo:
When no nexthop host name is specified, the destination domain name is
used instead. For example, the following directs mail for email@example.com
via the slow transport to a mail exchanger for foo.org. The slow
transport could be something that runs at most one delivery process at
When no transport is specified, Postfix uses the transport that matches
the address domain class (see TRANSPORT FIELD discussion above). The
following sends all mail for foo.org and its subdomains to host gate-
In the above example, the  are used to suppress MX lookups. The
result would likely point to your local machine.
In the case of delivery via SMTP, one may specify hostname:service
instead of just a host:
This directs mail for firstname.lastname@example.org to host bar.org port 2025. Instead
of a numerical port a symbolic name may be used. Specify  around the
hostname in order to disable MX lookups.
The error mailer can be used to bounce mail:
.foo.org error:mail for *.foo.org is not deliverable
This causes all mail for email@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
domain being looked up. Thus, some.domain.hierarchy is not broken up
into parent domains.
Patterns are applied in the order as specified in the table, until a
pattern is found that matches the search string.
Results are the same as with indexed file lookups, with the additional
feature that parenthesized substrings from the pattern can be interpo-
lated as $1, $2 and so on.
The following main.cf parameters are especially relevant to this topic.
See the Postfix main.cf file for syntax details and for default values.
Use the postfix reload command after a configuration change.
The address that is looked up instead of the null sender
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.
postmap(1) create mapping table
trivial-rewrite(8) rewrite and resolve addresses
pcre_table(5) format of PCRE tables
regexp_table(5) format of POSIX regular expression tables
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Yorktown Heights, NY 10598, USA