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6.1.2 Virtual domains

Postfix 2.0 supports ``virtual alias domains'', essentially what used to be called ``Postfix-style virtual domains'' in earlier Postfix versions. To make virtual alias domains work with Mailman, you need to do some setup in both Postfix and Mailman. Mailman will write all virtual alias mappings to a file called, by default, /usr/local/mailman/data/virtual-mailman. It will also use postmap to create the virtual-mailman.db file that Postfix will actually use.

First, you need to set up the Postfix virtual alias domains as described in the Postfix documentation (see Postfix's `virtual(5)` manpage). Note that it's your responsibility to include the `virtual-alias.domain anything` line as described manpage; Mailman will not include this line in virtual-mailman. You are highly encouraged to make sure your virtual alias domains are working properly before integrating with Mailman.

Next, add a path to Postfix's virtual_alias_maps variable, pointing to the virtual-mailman file, e.g.:

        virtual_alias_maps = <your normal virtual alias files>,
            hash:/usr/local/mailman/data/virtual-mailman

assuming you've installed Mailman in the default location. If you're using an older version of Postfix which doesn't have the virtual_alias_maps variable, use the virtual_maps variable instead.

Next, in your mm_cfg.py file, you will want to set the variable POSTFIX_STYLE_VIRTUAL_DOMAINS to the list of virtual domains that Mailman should update. This may not be all of the virtual alias domains that your Postfix installation supports! The values in this list will be matched against the host_name attribute of mailing lists objects, and must be an exact match.

Here's an example. Say that Postfix is configured to handle the virtual domains `dom1.ain`, `dom2.ain`, and `dom3.ain`, and further that in your main.cf file you've got the following settings:

        myhostname = mail.dom1.ain
        mydomain = dom1.ain
        mydestination = $myhostname, localhost.$mydomain
        virtual_alias_maps =
            hash:/some/path/to/virtual-dom1,
            hash:/some/path/to/virtual-dom2,
            hash:/some/path/to/virtual-dom2

If in your virtual-dom1 file, you've got the following lines:

        dom1.ain  IGNORE
        @dom1.ain @mail.dom1.ain

this tells Postfix to deliver anything addressed to `dom1.ain` to the same mailbox at `mail.dom1.com`, its default destination.

In this case you would not include `dom1.ain` in POSTFIX_STYLE_VIRTUAL_DOMAINS because otherwise Mailman will write entries for mailing lists in the dom1.ain domain as

        mylist@dom1.ain         mylist
        mylist-request@dom1.ain mylist-request
        # and so on...

The more specific entries trump your more general entries, thus breaking the delivery of any `dom1.ain` mailing list.

However, you would include `dom2.ain` and `dom3.ain` in mm_cfg.py:

        POSTFIX_STYLE_VIRTUAL_DOMAINS = ['dom2.ain', 'dom3.ain']

Now, any list that Mailman creates in either of those two domains, will have the correct entries written to /usr/local/mailman/data/virtual-mailman.

As above with the data/aliases* files, you want to make sure that both data/virtual-mailman and data/virtual-mailman.db are user and group owned by `mailman`.