I finally have this server working behind a NAT device and with spilt-DNS. This time when I installed Zimbra it used mail.example.com as the domain. I was able to add another domain, example.com, after the install was complete. Now when I add a new user under example.com I have to set an alias to mail.example.com for it to work. Does it have to work this way? During the install is there a way to change the domain name. I was never prompted.