CANONICAL(5)

NAME
canonical - format of Postfix canonical table

SYNOPSIS
postmap /etc/postfix/canonical
postmap -q "string" /etc/postfix/canonical
postmap -q - /etc/postfix/canonical <inputfile

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, or lookups can be directed to TCP-based server. In that case, the lookups are done in a slightly different way as described below under "REGULAR EXPRESSION TABLES" and "TCP-BASED TABLES". 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 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 `#'.

multi-line text
    A logical line starts with non-whitespace text. A line that starts with whitespace continues a logical line.

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 is 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 or $proxy_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 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 propagated 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 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 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). 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. Results are the same as with indexed file lookups.

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.

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

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.

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

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.

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
tcp_table(5) TCP client/server table lookup protocol

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