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 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] des-
tinations 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
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 expres-
sions, 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 logi-
cal 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 nex-
thop.
.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 par-
ent_domain_matches_subdomains configuration set-
ting. 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-dae-
mon@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 informa-
tion 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 trans-
port 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 host-
name: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 ta-
ble, 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 descrip-
tion of the TCP client/server lookup protocol, see tcp_ta-
ble(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 pat-
terns 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
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)