Postfix virtual transport

This is a variation on the Postfix virtual mailbox example. Again, every hosted address can have its own mailbox.

While non-Postfix software is being used for final delivery, some Postfix concepts are still needed in order to glue everything together. For additional background on this glue you may want to take a look at the virtual mailbox domain class as defined in the ADDRESS_CLASS_README file.

The text in this section describes what things should look like from Postfix's point of view. See CYRUS_README or MAILDROP_README for specific information about Cyrus or about Courier maildrop.

Here is an example for a hosted domain example.com that delivers to a non-Postfix delivery agent:

 1 /etc/postfix/main.cf:
 2     virtual_transport = ...see below...
 3     virtual_mailbox_domains = example.com ...more domains...
 4     virtual_mailbox_maps = hash:/etc/postfix/vmailbox
 5     virtual_alias_maps = hash:/etc/postfix/virtual
 6 
 7 /etc/postfix/vmailbox:
 8     info@example.com    whatever
 9     sales@example.com   whatever
10     # Comment out the entry below to implement a catch-all.
11     # Configure the mailbox store to accept all addresses.
12     # @example.com      whatever
13     ...virtual mailboxes for more domains...
14 
15 /etc/postfix/virtual:
16     postmaster@example.com postmaster

Notes:

• Line 2: With delivery to a non-Postfix mailbox store for hosted domains, the virtual_transport parameter usually specifies the Postfix LMTP client, or the name of a master.cf entry that executes non-Postfix software via the pipe delivery agent. Typical examples (use only one):

  virtual_transport = lmtp:unix:/path/name (uses UNIX-domain socket)
  virtual_transport = lmtp:hostname:port   (uses TCP socket)
  virtual_transport = maildrop:            (uses pipe(8) to command)

Postfix comes ready with support for LMTP. And an example maildrop delivery method is already defined in the default Postfix master.cf file. See the MAILDROP_README document for more details.

• Line 3: The virtual_mailbox_domains setting tells Postfix that example.com is delivered via the virtual_transport that was discussed in the previous paragraph. If you omit this virtual_mailbox_domains setting then Postfix will either reject mail (relay access denied) or will not be able to deliver it (mail for example.com loops back to myself).

NEVER list a virtual MAILBOX domain name as a mydestination domain!

NEVER list a virtual MAILBOX domain name as a virtual ALIAS domain!

• Lines 4, 7-13: The virtual_mailbox_maps parameter specifies the lookup table with all valid recipient addresses. The lookup result is ignored by Postfix. In the above example, info@example.com and sales@example.com are listed as valid addresses, and mail for anything else is rejected with "User unknown". If you intend to use LDAP, MySQL or PgSQL instead of local files, be sure to review the "local files versus databases" section at the top of this document!

• Line 12: The commented out entry (text after #) shows how one would inform Postfix of the existence of a catch-all address. Again, the lookup result is ignored by Postfix.

NEVER put a virtual MAILBOX wild-card in the virtual ALIAS file!!

Note: if you specify a wildcard in virtual_mailbox_maps, then you still need to configure the non-Postfix mailbox store to receive mail for any address in that domain.

• Lines 5, 15, 16: As you see above, it is possible to mix virtual aliases with virtual mailboxes. We use this feature to redirect mail for example.com's postmaster address to the local postmaster. You can use the same mechanism to redirect any addresses to a local or remote address.

• Line 16: This example assumes that in main.cf, $myorigin is listed under the mydestination parameter setting. If that is not the case, specify an explicit domain name on the right-hand side of the virtual alias table entries or else mail will go to the wrong domain.

Execute the command "postmap /etc/postfix/virtual" after changing the virtual file, execute "postmap /etc/postfix/vmailbox" after changing the vmailbox file, and execute the command "postfix reload" after changing the main.cf file.