Ubuntu Manpage: canonical - Postfix canonical table format

Provided by: postfix_3.7.4-2build1_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)