I just finished configuring Zimbra and I have two domains hosted on my internal DNS (domain-1 and domain-2) all using the .LAN TLD (ex. domain-1.lan). I am able to send messages internally but I am unable to send messages to a user externally.
My setup is such like this, I own the domain domain-2.com and I have my internal DNS setup for domain-2.lan. I have Zimbra fetch messages from the domain-2.com mail server to the local accounts on domain-2.lan. Now I want to be able to send a message from my internal network to the outside (yahoo.com, hotmail, and even domain-2.com)