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
Wietse Venema
Google, Inc.
111 8th Avenue
New York, NY 10011, USA