Following an upgrade from 5.0.20 32 bit (Fedora 7) to 7.2.0 64 bit (Ubuntu 8.04), with the requisite tweaking that seems to follow the process (as noted in many threads), all would appear well at first glance, but messages are just queuing up on the MTA box and never getting transferred to the Store servers.

(MTA Server plus four Store servers)

zmcontrol reports all services running on all of the servers, though the 'server status' tab on the Admin Console shows all servers down except for the number 2 Store Server which is also the logger server.

Mail Queues tab shows all of the messages queuing up.
DNS has been tested extensively, and should not be an issue.
The edits to the /etc/hosts files have been made as noted in various threads.

I can log into established mail accounts and the admin console.

Watching the zimbra.log file on the MTA server, I see the occasional entry:

May 12 22:35:12 mail postfix/lmtp[16547]: BFBE8C8D96: to=, relay=mail3.midwest-connections.com[69.148.152.18]:7025, delay=1151, delays=1150/0.01/0.01/0.87, dsn=2.1.5, status=sent (250 2.1.5 Delivery OK)

Which would appear to indicate that the system can move messages, so why is it not processing the 'live' traffic???

Any suggestions/guidance would be greatly appreciated.