CANONICAL(5) CANONICAL(5)
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 map-
ping 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 expres-
sions, 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 mes-
sages) 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 head-
ers from remote SMTP clients only if the client matches
the local_header_rewrite_clients parameter, or if the
remote_header_rewrite_domain configuration parameter spec-
ifies a non-empty value. To get the behavior before Post-
fix 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 vir-
tual 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 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 logi-
cal 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 pro-
duce 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
$proxy_interfaces.
This form is useful for replacing login names by
Firstname.Lastname.
@domain address
Replace other addresses in domain by address. This
form has the lowest precedence.
Note: @domain is a wild-card. When this form is
applied to recipient addresses, the Postfix SMTP
server accepts mail for any recipient in domain,
regardless of whether that recipient exists. This
may turn your mail system into a backscatter
source: Postfix first accepts mail for non-existent
recipients and then tries to return that mail as
"undeliverable" to the often forged sender address.
RESULT ADDRESS REWRITING
The lookup result is subject to address rewriting:
o When the result has the form @otherdomain, the
result becomes the same user in otherdomain.
o When "append_at_myorigin=yes", append "@$myorigin"
to addresses without "@domain".
o When "append_dot_mydomain=yes", append ".$mydomain"
to addresses without ".domain".
ADDRESS EXTENSION
When a mail address localpart contains the optional recip-
ient 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 propa-
gated 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 ta-
ble, 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 descrip-
tion of the TCP client/server lookup protocol, see tcp_ta-
ble(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 mecha-
nisms 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 Post-
fix 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 transla-
tor.
masquerade_classes
List of address classes subject to masquerading:
zero or more of envelope_sender, envelope_recipi-
ent, header_sender, header_recipient.
masquerade_domains
List of domains that hide their subdomain struc-
ture.
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, re-
write 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
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)