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.
SEE ALSO
cleanup(8), canonicalize and enqueue mail
postmap(1), Postfix lookup table manager
postconf(5), configuration parameters
virtual(5), virtual aliasing
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