canonical - Postfix canonical table format at Linux.org

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CANONICAL(5) File Formats Manual CANONICAL(5)

NAME
canonical - Postfix canonical table format

SYNOPSIS
postmap /etc/postfix/canonical

postmap -q "string" /etc/postfix/canonical

postmap -q - /etc/postfix/canonical <inputfile

DESCRIPTION
The optional canonical(5) table specifies an address mapping for local and non-local addresses. The mapping is
used by the cleanup(8) daemon, before mail is stored into the queue. The address mapping is recursive.

Normally, the canonical(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/canonical" to rebuild an indexed file after changing the corresponding text
file.

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 cases, the lookups are done in a
slightly different way as described below under "REGULAR EXPRESSION TABLES" or "TCP-BASED TABLES".

By default the canonical(5) mapping affects both message header addresses (i.e. addresses that appear inside
messages) and message envelope addresses (for example, the addresses that are used in SMTP protocol commands).
This is controlled with the canonical_classes parameter.

NOTE: Postfix versions 2.2 and later rewrite message headers from remote SMTP clients only if the client
matches the local_header_rewrite_clients parameter, or if the remote_header_rewrite_domain configuration
parameter specifies a non-empty value. To get the behavior before Postfix 2.2, specify "local_header_re‐
write_clients = static:all".

Typically, one would use the canonical(5) table to replace login names by Firstname.Lastname, or to clean up
addresses produced by legacy mail systems.

The canonical(5) mapping is not to be confused with virtual alias support or with local aliasing. To change
the destination but not the headers, use the virtual(5) or aliases(5) map instead.

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 a mail address, replace it by 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 `#'.

Firstname.Lastname style addresses, but see below for a simpler solution.

user address
Replace user@site by address when site is equal to $myorigin, when site is listed in $mydestination, or
when it is listed in $inet_interfaces or $proxy_interfaces.

This form is useful for replacing login names by Firstname.Lastname.

@domain address
Replace other addresses in domain by address. This form has the lowest precedence.

Note: @domain is a wild-card. When this form is applied to recipient addresses, the Postfix SMTP server
accepts mail for any recipient in domain, regardless of whether that recipient exists. This may turn
your mail system into a backscatter source: Postfix first accepts mail for non-existent recipients and
then tries to return that mail as "undeliverable" to the often forged sender address.

RESULT ADDRESS REWRITING
The lookup result is subject to address rewriting:

· When the result has the form @otherdomain, the result becomes the same user in otherdomain.

· When "append_at_myorigin=yes", append "@$myorigin" to addresses without "@domain".

· When "append_dot_mydomain=yes", append ".$mydomain" to addresses without ".domain".

ADDRESS EXTENSION
When a mail address localpart contains the optional recipient delimiter (e.g., user+foo@domain), the lookup
order becomes: user+foo@domain, user@domain, user+foo, user, and @domain.

The propagate_unmatched_extensions parameter controls whether an unmatched address extension (+foo) is propa‐
gated to the result of table lookup.

REGULAR EXPRESSION TABLES
This section describes how the table lookups change when the table is given in the form of regular expres‐
sions. 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, user@domain
mail addresses are not broken up into their user and @domain constituent parts, nor is user+foo broken up into
user and foo.

Patterns are applied in the order as specified in the table, until a pattern is found that matches the search
string.

Results are the same as with indexed file lookups, with the additional feature that parenthesized substrings
from the pattern can be interpolated as $1, $2 and so on.

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 address once. Thus, user@domain mail addresses are not broken up into
their user and @domain constituent parts, nor is user+foo broken up into user and foo.

canonical_maps
List of canonical mapping tables.

recipient_canonical_maps
Address mapping lookup table for envelope and header recipient addresses.

sender_canonical_maps
Address mapping lookup table for envelope and header sender addresses.

propagate_unmatched_extensions
A list of address rewriting or forwarding mechanisms that propagate an address extension from the orig‐
inal address to the result. Specify zero or more of canonical, virtual, alias, forward, include, or
generic.

Other parameters of interest:

inet_interfaces
The network interface addresses that this system receives mail on. You need to stop and start Postfix
when this parameter changes.

local_header_rewrite_clients
Rewrite message header addresses in mail from these clients and update incomplete addresses with the
domain name in $myorigin or $mydomain; either don't rewrite message headers from other clients at all,
or rewrite message headers and update incomplete addresses with the domain specified in the
remote_header_rewrite_domain parameter.

proxy_interfaces
Other interfaces that this machine receives mail on by way of a proxy agent or network address transla‐
tor.

masquerade_classes
List of address classes subject to masquerading: zero or more of envelope_sender, envelope_recipient,
header_sender, header_recipient.

masquerade_domains
List of domains that hide their subdomain structure.

masquerade_exceptions
List of user names that are not subject to address masquerading.

mydestination
List of domains that this mail system considers local.

myorigin
The domain that is appended to locally-posted mail.

owner_request_special
Give special treatment to owner-xxx and xxx-request addresses.

remote_header_rewrite_domain
Don't rewrite message headers from remote clients at all when this parameter is empty; otherwise, re‐
write message headers and append the specified domain name to incomplete addresses.