I have installed the Open Source Edition on Ubuntu and the server is behind a router. The purpose of the ZCS is to retrieve mails from an external POP server and being able to send mails out. I have set up an internal domain internaldom.local and a local user localuser. Then I set up the external domain externaldom.com and have given the user an alias of email@example.com. This way I can send mails that show the external domain instead of the local domain.
The problem is that I cannot send mails to other users on this external domain because the ZCS thinks that it is an internal domain (Error: bounce). How can I tell the ZCS that this is an external domain?