Get the default configuration file canonical for Postfix, optimized for CentOS Linux 8. This example configuration ensures optimal compatibility and performance for Postfix, making it easy to set up and adjust to meet your needs.
Find and download the configuration file here: /etc/postfix/canonical.
For more configurations and setup guides, visit our related files section to further customize your system.
# 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 regu-
# lar-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 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 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 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, 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 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
# Use "postconf readme_directory" or "postconf html_direc-
# tory" 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)
Download the raw file with wget or curl
wget -O canonical.example https://exampleconfig.com/static/raw/postfix/centos8/etc/postfix/canonical
curl https://exampleconfig.com/static/raw/postfix/centos8/etc/postfix/canonical > canonical.example
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