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Postfix Documentation
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Postfix on a local network

This section describes a local area network environment of one main server and multiple other systems that send and receive email. As usual we assume that the Internet domain name is "example.com". All systems are configured to send mail as "[email protected]", and all systems receive mail for "[email protected]". The main server also receives mail for "[email protected]". We call this machine by the name of mailhost.example.com.

A drawback of sending mail as "[email protected]" is that mail for "root" and other system accounts is also sent to the central mailhost. See the section " Delivering some but not all accounts locally" below for possible solutions.

As usual, the examples show only parameters that are not left at their default settings.

First we present the non-mailhost configuration, because it is the simpler one. This machine sends mail as "[email protected]" and is final destination for "[email protected]".

1 /etc/postfix/
main.cf:
2     
myorigin = $
mydomain
3     
mynetworks = 127.0.0.0/8 10.0.0.0/24
4     
relay_domains =
5     # Optional: forward all non-local mail to mailhost
6     #
relayhost = $
mydomain

Translation:

  • Line 2: Send mail as "[email protected]".

  • Line 3: Specify the trusted networks.

  • Line 4: This host does not relay mail from untrusted networks.

  • Line 6: This is needed if no direct Internet access is available. See also below, " Postfix behind a firewall".

Next we present the mailhost configuration. This machine sends mail as "[email protected]" and is final destination for "[email protected]" as well as "[email protected]".

 1 DNS:
 2     example.com    IN    MX  10 mailhost.example.com.
 3 
 4 /etc/postfix/
main.cf:
 5     
myorigin = $
mydomain
 6     
mydestination = $
myhostname localhost.$
mydomain localhost $
mydomain
 7     
mynetworks = 127.0.0.0/8 10.0.0.0/24
 8     
relay_domains =
 9     # Optional: forward all non-local mail to firewall
10     #
relayhost = [firewall.example.com]

Translation:

  • Line 2: Send mail for the domain "example.com" to the machine mailhost.example.com. Remember to specify the "." at the end of the line.

  • Line 5: Send mail as "[email protected]".

  • Line 6: This host is the final mail destination for the "example.com" domain, in addition to the names of the machine itself.

  • Line 7: Specify the trusted networks.

  • Line 8: This host does not relay mail from untrusted networks.

  • Line 10: This is needed only when the mailhost has to forward non-local mail via a mail server on a firewall. The [] forces Postfix to do no MX record lookups.

In an environment like this, users access their mailbox in one or more of the following ways:

  • Mailbox access via NFS or equivalent.

  • Mailbox access via POP or IMAP.

  • Mailbox on the user's preferred machine.

In the latter case, each user has an alias on the mailhost that forwards mail to her preferred machine:

/etc/aliases:
    joe:    [email protected]
    jane:   [email protected]

On some systems the alias database is not in /etc/aliases. To find out the location for your system, execute the command "postconf alias_maps".

Execute the command "newaliases" whenever you change the aliases file.

Postfix Documentation
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