Ubuntu Manpage: canonical - Postfix canonical table format

Provided by: postfix_2.11.0-1ubuntu1.2_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 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, patterns are tried in the order as listed below:

       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.

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
What addresses are subject to canonical address mapping.

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, 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 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.

remote_header_rewrite_domain
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

                                                                                     CANONICAL(5)