Postfix transport configuration example for CentOS Linux 8

Get the default configuration file transport 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/transport.

For more configurations and setup guides, visit our related files section to further customize your system.

    # TRANSPORT(5)                                                      TRANSPORT(5)
# 
# NAME
#        transport - Postfix transport table format
# 
# SYNOPSIS
#        postmap /etc/postfix/transport
# 
#        postmap -q "string" /etc/postfix/transport
# 
#        postmap -q - /etc/postfix/transport <inputfile
# 
# DESCRIPTION
#        The  optional  transport(5) table specifies a mapping from
#        email  addresses  to  message  delivery   transports   and
#        next-hop  destinations.   Message delivery transports such
#        as local or smtp are defined in the  master.cf  file,  and
#        next-hop destinations are typically hosts or domain names.
#        The table is searched by the trivial-rewrite(8) daemon.
# 
#        This  mapping  overrides  the  default   transport:nexthop
#        selection that is built into Postfix:
# 
#        local_transport (default: local:$myhostname)
#               This  is  the default for final delivery to domains
#               listed with mydestination, and for [ipaddress] des-
#               tinations    that    match    $inet_interfaces   or
#               $proxy_interfaces. The default nexthop  destination
#               is the MTA hostname.
# 
#        virtual_transport (default: virtual:)
#               This  is  the default for final delivery to domains
#               listed with  virtual_mailbox_domains.  The  default
#               nexthop destination is the recipient domain.
# 
#        relay_transport (default: relay:)
#               This  is the default for remote delivery to domains
#               listed with relay_domains. In order  of  decreasing
#               precedence,  the  nexthop destination is taken from
#               relay_transport,   sender_dependent_relayhost_maps,
#               relayhost, or from the recipient domain.
# 
#        default_transport (default: smtp:)
#               This  is  the  default for remote delivery to other
#               destinations.  In order of  decreasing  precedence,
#               the nexthop destination is taken from sender_depen-
#               dent_default_transport_maps,     default_transport,
#               sender_dependent_relayhost_maps, relayhost, or from
#               the recipient domain.
# 
#        Normally, the transport(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/transport"  to  rebuild  an  indexed
#        file after changing the corresponding transport table.
# 
#        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 case, the lookups are done in a  slightly
#        different way as described below under "REGULAR EXPRESSION
#        TABLES" or "TCP-BASED TABLES".
# 
# 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  the  recipient  address  or
#               domain, use 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.
# 
#        The  pattern specifies an email address, a domain name, or
#        a domain name hierarchy, as described  in  section  "TABLE
#        LOOKUP".
# 
#        The  result is of the form transport:nexthop and specifies
#        how or where to deliver mail. This is described in section
#        "RESULT FORMAT".
# 
# 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+extension@domain transport:nexthop
#               Deliver   mail  for  user+extension@domain  through
#               transport to nexthop.
# 
#        user@domain transport:nexthop
#               Deliver mail for user@domain through  transport  to
#               nexthop.
# 
#        domain transport:nexthop
#               Deliver  mail  for domain through transport to nex-
#               thop.
# 
#        .domain transport:nexthop
#               Deliver mail for any subdomain  of  domain  through
#               transport  to  nexthop.  This applies only when the
#               string transport_maps is not  listed  in  the  par-
#               ent_domain_matches_subdomains   configuration  set-
#               ting.  Otherwise, a domain name matches itself  and
#               its subdomains.
# 
#        * transport:nexthop
#               The  special pattern * represents any address (i.e.
#               it functions  as  the  wild-card  pattern,  and  is
#               unique to Postfix transport tables).
# 
#        Note  1:  the  null  recipient  address  is  looked  up as
#        $empty_address_recipient@$myhostname (default: mailer-dae-
#        mon@hostname).
# 
#        Note  2:  user@domain  or  user+extension@domain lookup is
#        available in Postfix 2.0 and later.
# 
# RESULT FORMAT
#        The lookup result is of the form  transport:nexthop.   The
#        transport  field  specifies a mail delivery transport such
#        as smtp or local. The nexthop field  specifies  where  and
#        how to deliver mail.
# 
#        The  transport field specifies the name of a mail delivery
#        transport (the first name of a mail delivery service entry
#        in the Postfix master.cf file).
# 
#        The  interpretation  of  the  nexthop  field  is transport
#        dependent. In the case of SMTP, specify  a  service  on  a
#        non-default  port  as  host:service,  and disable MX (mail
#        exchanger) DNS lookups with [host] or [host]:port. The  []
#        form is required when you specify an IP address instead of
#        a hostname.
# 
#        A null transport and null nexthop  result  means  "do  not
#        change":  use  the delivery transport and nexthop informa-
#        tion that would be used when the  entire  transport  table
#        did not exist.
# 
#        A  non-null  transport  field  with  a  null nexthop field
#        resets the nexthop information to the recipient domain.
# 
#        A null transport field with non-null  nexthop  field  does
#        not modify the transport information.
# 
# EXAMPLES
#        In  order to deliver internal mail directly, while using a
#        mail relay for all other mail, specify a  null  entry  for
#        internal  destinations  (do not change the delivery trans-
#        port or the nexthop information) and  specify  a  wildcard
#        for all other destinations.
# 
#             my.domain    :
#             .my.domain   :
#             *            smtp:outbound-relay.my.domain
# 
#        In  order  to send mail for example.com and its subdomains
#        via the uucp transport to the UUCP host named example:
# 
#             example.com      uucp:example
#             .example.com     uucp:example
# 
#        When no nexthop host name is  specified,  the  destination
#        domain  name  is  used instead. For example, the following
#        directs mail for user@example.com via the  slow  transport
#        to  a  mail exchanger for example.com.  The slow transport
#        could be configured to run at most one delivery process at
#        a time:
# 
#             example.com      slow:
# 
#        When no transport is specified, Postfix uses the transport
#        that matches the address  domain  class  (see  DESCRIPTION
#        above).   The following sends all mail for example.com and
#        its subdomains to host gateway.example.com:
# 
#             example.com      :[gateway.example.com]
#             .example.com     :[gateway.example.com]
# 
#        In the above example, the [] suppress  MX  lookups.   This
#        prevents  mail  routing loops when your machine is primary
#        MX host for example.com.
# 
#        In the case of delivery via SMTP, one  may  specify  host-
#        name:service instead of just a host:
# 
#             example.com      smtp:bar.example:2025
# 
#        This directs mail for user@example.com to host bar.example
#        port 2025. Instead of a numerical port a symbolic name may
#        be used. Specify [] around the hostname if MX lookups must
#        be disabled.
# 
#        The error mailer can be used to bounce mail:
# 
#             .example.com     error:mail for *.example.com is not deliverable
# 
#        This causes all mail for user@anything.example.com  to  be
#        bounced.
# 
# 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,
#        some.domain.hierarchy is not  looked  up  via  its  parent
#        domains,  nor is user+foo@domain looked up as user@domain.
# 
#        Patterns are applied in the order as specified in the  ta-
#        ble,  until  a  pattern  is  found that matches the search
#        string.
# 
#        The trivial-rewrite(8) server disallows regular expression
#        substitution  of  $1  etc.  in  regular  expression lookup
#        tables, because that could open a security  hole  (Postfix
#        version 2.3 and later).
# 
# 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 recipient address
#        once.  Thus, some.domain.hierarchy is not  looked  up  via
#        its  parent  domains,  nor is user+foo@domain looked up as
#        user@domain.
# 
#        Results are the same as with indexed file lookups.
# 
# 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.
# 
#        empty_address_recipient
#               The address that is looked up instead of  the  null
#               sender address.
# 
#        parent_domain_matches_subdomains
#               List  of  Postfix features that use domain.tld pat-
#               terns  to  match  sub.domain.tld  (as  opposed   to
#               requiring .domain.tld patterns).
# 
#        transport_maps
#               List of transport lookup tables.
# 
# SEE ALSO
#        trivial-rewrite(8), rewrite and resolve addresses
#        master(5), master.cf file format
#        postconf(5), configuration parameters
#        postmap(1), Postfix lookup table manager
# 
# README FILES
#        Use  "postconf  readme_directory" or "postconf html_direc-
#        tory" to locate this information.
#        ADDRESS_REWRITING_README, address rewriting guide
#        DATABASE_README, Postfix lookup table overview
#        FILTER_README, external content filter
# 
# 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
# 
#                                                                   TRANSPORT(5)

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