I've got an existing IMAP server that all of my mail goes through.
Call the domain foo.com, so my mail server is mail.foo.com.
I've set up Zimbra as zimbra.foo.com.
I've set up an external account for mail.foo.com.
Mail from firstname.lastname@example.org to email@example.com works fine.
Mail from firstname.lastname@example.org to the outside world works fine.
Mail from email@example.com to firstname.lastname@example.org FAILS.
I've found things about how to forward a single machine (like zimbra.foo.com) but nothing to say how to forward everything in a domain EXCEPT a single machine.
Perhaps I'm on the wrong track...
Any ideas out there?