This would be fairly easy to do, assuming that users in each Windows domain
have their own subdomain name in their external FQDN email adresses. For example:

user1@sales.mydomain.com
user1@arts.mydomain.com

Then it can be done with Postfix transport_maps in the transport file:

@sales.mydomain.com smtp:[sales.mydomain.com]
@arts.mydomain.com smtp:[arts.mydomain.com]

But it gets more difficult if all the external internet address are in the
same domain, such as user@mydomain.com. Then you need to have a lookup table
for each user account. This can be done in a local file on the Postfix box, or
it can be an LDAP query to an LDAP database.

That situaiton could be done in the transport file by adding an entry for each user:

user1@domain.com smtp:[sales.mydomain.com]
user2@domain.com smtp:[arts.mydomain.com]

The Postfix solution that you choose, depends upon a lot of different variables, mostly
having to do with your particular domain naming conventions, DNS structure, LDAP availability, etc.
Depending on what those are, you might be able to use other Postfix features instead of transport, such as
aliases, virtual_aliases, recipient_canonical maps, etc. etc.

Reference: man 5 postconf

--
Greg





Dave wrote:
> Hi,
>
> I have two windows domains. They are both independent of each other and
> both in the format sales.local and art.local, I do not want to change
> the domains structure.
>
> Sales.local currently has exchange on it. Sales is attached to the
> postfix mail relay by way of an additional NIC on a different subnet.
> The postfix machine then has a card on the same subnet as the exchange
> servers additonal card and pushes the email to it from there.
>
> My question is this. I propose putting an additional card in both the
> art server and the postfix machine. Putting both the additoinal card on
> the same subnet as each other.
>
> Can I set postfix to push email destined for certain users to one card
> rather than the other?
> Where would I go to do this?
> Does this sound like the best solution considering my desire not to
> change the domain structure.
>
> Thanks
>
> Dave
>