Ubuntu Manpage: canonical - Postfix canonical table format

Provided by: postfix_3.8.6-1build2_amd64

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

       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.

TABLE SEARCH ORDER

With lookups from indexed files such as DB or DBM, or from networked tables such as NIS, LDAP or SQL,
each user@domain query produces a sequence of query patterns as described below.

Each query pattern is sent to each specified lookup table before trying the next query pattern, until a
match is found.

user@domain address
Replace user@domain 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
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.

To avoid backscatter with mail for a wild-card domain, replace the wild-card mapping with explicit
1:1 mappings, or add a reject_unverified_recipient restriction for that domain:

smtpd_recipient_restrictions =
...
reject_unauth_destination
check_recipient_access
inline:{example.com=reject_unverified_recipient}
unverified_recipient_reject_code = 550

In the above example, Postfix may contact a remote server if the recipient is rewritten to a
remote 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
       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).  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.

       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. The text below provides only a parameter
summary. See postconf(5) for more details including examples.

canonical_classes (envelope_sender, envelope_recipient, header_sender, header_recipient)
What addresses are subject to canonical_maps address mapping.

canonical_maps (empty)
Optional address mapping lookup tables for message headers and envelopes.

recipient_canonical_maps (empty)
Optional address mapping lookup tables for envelope and header recipient addresses.

sender_canonical_maps (empty)
Optional address mapping lookup tables for envelope and header sender addresses.

propagate_unmatched_extensions (canonical, virtual)
What address lookup tables copy an address extension from the lookup key to the lookup result.

Other parameters of interest:

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

local_header_rewrite_clients (permit_inet_interfaces)
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 (empty)
The network interface addresses that this mail system receives mail on by way of a proxy or
network address translation unit.

masquerade_classes (envelope_sender, header_sender, header_recipient)
What addresses are subject to address masquerading.

masquerade_domains (empty)
Optional list of domains whose subdomain structure will be stripped off in email addresses.

masquerade_exceptions (empty)
Optional list of user names that are not subjected to address masquerading, even when their
addresses match $masquerade_domains.

mydestination ($myhostname, localhost.$mydomain, localhost)
The list of domains that are delivered via the $local_transport mail delivery transport.

myorigin ($myhostname)
The domain name that locally-posted mail appears to come from, and that locally posted mail is
delivered to.

owner_request_special (yes)
Enable special treatment for owner-listname entries in the aliases(5) file, and don't split
owner-listname and listname-request address localparts when the recipient_delimiter is set to "-".

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

README FILES

       Use "postconf readme_directory" or "postconf html_directory" to locate this information.
       DATABASE_README, Postfix lookup table overview
       ADDRESS_REWRITING_README, address rewriting guide

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

                                                                                                    CANONICAL(5)