TRANSPORT(5) 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 trans-
ports 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 [ipad-dress] [ipaddress]
dress] destinations that match $inet_interfaces or $proxy_interfaces. The default nexthop des-tination destination
tination 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_depen-dent_relayhost_maps, sender_dependent_relayhost_maps,
dent_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 prece-dence, precedence,
dence, the nexthop destination is taken from default_transport, sender_dependent_relay-host_maps, sender_dependent_relayhost_maps,
host_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 chang-ing changing
ing 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 reg-ular regular
ular 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.
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).
Note 3: 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 deliv-ery delivery
ery service entry in the Postfix master.cf file).
The interpretation of the nexthop field is transport dependent. In the case of SMTP, specify a ser-vice service
vice 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 nex-thop nexthop
thop 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 informa-tion) information)
tion) 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 exam-ple.com. example.com.
ple.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 gate-way.example.com: gateway.example.com:
way.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 expres-sion expression
sion 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
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
TRANSPORT(5)
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