I have a unique situation and am looking for clean solution.
I need to have Zimbra treat any mail that is created by act of a forwarding rule different from other messages. I would like to get it to add a custom header or send the mail to a different IP address than the rest of the mail, which is all going to a specific IP for relay now.
I'd love to find something which would survive an upgrade of Zimbra but barring that, just something which I could do easily after each upgrade would work fine as well.
Any ideas from the Postfix masters out there?