I recently moved from a 32bit to 64bit RHEL 6.x server and Zimbra 7.x Network version - also 64bit. The whole migration went fine and worked well from behind my NAT router.
I decided to move out from behind it to our WAN router that has static addresses 74.xx.xx.94 to 74.xx.xx.98 available. I made the required changes at Network Solutions to remove my DNS machine from my records and keep the MX address the same 74.xx.xx.94 and moved my private net work router (NAT) to 74.xx.xx.95.
After making those changes and checking the rhel resolv, hosts, hostname files. I thought I was set? The server is plugged directly into the WAN router with eth0 set to 192.168.0.x and eth1 set to 74.xx.xx.94. dnsmaq is setup for simple caching internal dns.
Note: I have tested so far with rhel firewall and without.... no change in results.
Zimbra sees the MX fine and I am able to send mail but none returning when testing mail (send to work and sending back) failure. Something is keeping me from getting mail. ...btw my static IP's from ATT all have port 25 open. I have also opened one additional port for admin 7071. My Zimbra server should be allowing "both" http and https access from outside. It is not working.
I am still unable to receive mail. Scratching my head on this one..... Any help would be greatly appreciated to help debug.