# phpman > man > transport(5) [TRANSPORT(5)](https://www.chedong.com/phpMan.php/man/TRANSPORT/5/markdown) File Formats Manual [TRANSPORT(5)](https://www.chedong.com/phpMan.php/man/TRANSPORT/5/markdown) ## 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)](https://www.chedong.com/phpMan.php/man/transport/5/markdown) 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)](https://www.chedong.com/phpMan.php/man/trivial-rewrite/8/markdown) 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)](https://www.chedong.com/phpMan.php/man/transport/5/markdown) table is specified as a text file that serves as input to the [**postmap**(1)](https://www.chedong.com/phpMan.php/man/postmap/1/markdown) 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)](https://www.chedong.com/phpMan.php/man/postmap/1/markdown) 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)](https://www.chedong.com/phpMan.php/man/table/5/markdown) or **pcre**___**[table**(5)](https://www.chedong.com/phpMan.php/man/table/5/markdown). 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)](https://www.chedong.com/phpMan.php/man/trivial-rewrite/8/markdown) 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)](https://www.chedong.com/phpMan.php/man/table/5/markdown). 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)](https://www.chedong.com/phpMan.php/man/postconf/5/markdown) 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)](https://www.chedong.com/phpMan.php/man/trivial-rewrite/8/markdown), rewrite and resolve addresses [master(5)](https://www.chedong.com/phpMan.php/man/master/5/markdown), master.cf file format [postconf(5)](https://www.chedong.com/phpMan.php/man/postconf/5/markdown), configuration parameters [postmap(1)](https://www.chedong.com/phpMan.php/man/postmap/1/markdown), 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)](https://www.chedong.com/phpMan.php/man/TRANSPORT/5/markdown)