CANONICAL(5)

NAME
canonical - format of Postfix canonical table

SYNOPSIS
postmap /etc/postfix/canonical

DESCRIPTION
The optional canonical table specifies an address mapping for local and non-local addresses. The mapping is used by the cleanup(8) daemon. The address mapping is recursive. Normally, the canonical 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 in order to rebuild the indexed file after changing the 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. In that case, the lookups are done in a slightly different way as described below. The canonical 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). Think Sendmail rule set S3, if you like. Typically, one would use the canonical table to replace login names by Firstname.Lastname, or to clean up addresses produced by legacy mail systems. The canonical mapping is not to be confused with virtual domain support. Use the virtual(5) map for that purpose. The canonical mapping is not to be confused with local aliasing. Use the aliases(5) map for that purpose.

TABLE FORMAT
The format of the canonical table is as follows:

blanks and comments
    Blank lines are ignored, as are lines beginning with `#'.

leading whitespace
    Lines that begin with whitespace continue the previous line.

pattern result
    When pattern matches a mail address, replace it by the corresponding result.

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@domain address
    user@domain is replaced by address. This form has the highest precedence.

    This form useful to clean up addresses produced by legacy mail systems. It can also be used to produce Firstname.Lastname style addresses, but see below for a simpler solution.

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

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

@domain address
    Every address in domain is replaced by address. This form has the lowest precedence.

In all the above forms, when address has the form @otherdomain, the result is the same user in otherdomain.

ADDRESS EXTENSION
When table lookup fails, and the address localpart contains the optional recipient delimiter (e.g., user+foo@domain), the search is repeated for the unextended address (e.g. user@domain), and the unmatched extension is propagated to the result of table lookup. The matching order is: user+foo@domain, user@domain, user+foo, user, and @domain.

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

BUGS
The table format does not understand quoting conventions.

CONFIGURATION PARAMETERS
The following main.cf parameters are especially relevant to this topic. See the Postfix main.cf file for syntax details and for default values. Use the postfix reload command after a configuration change.

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.

Other parameters of interest:

inet_interfaces
    The network interface addresses that this system receives mail on.

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.

SEE ALSO
cleanup(8) canonicalize and enqueue mail
postmap(1) create mapping table
virtual(5) virtual domain mapping
pcre_table(5) format of PCRE tables
regexp_table(5) format of POSIX regular expression tables

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