| TRANSPORT(5) | File Formats Manual | 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 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