I preformed a memory upgrade to my server a few days ago and left thinking everything was up and running fine. A few hours later I decided to check up on my new faster toy. I quickly found out I had no outgoing mail; nothing would pass through the virus scanner.
In a frantic search through the forums I quickly figured out the best solution was to upgrade to 5.0.4. I had reservations on doing this on-site let alone on a remote at 10:30 at night. It was however pointed out to me by my better half that "no mail is going out now anyway." With that succinct comment ringing in my ears, off I went.
45 minutes or so later and all was right with my e-mail world. No problems, no hangs. The only issue was restoring my restricted recipients list and settings. Not a big deal and I now have those files properly backed up and ready for the next upgrade.
Hats off to the Zimbra team! (what was I waiting for
)
Bugzilla
Wiki
Source
Upgrade from 4.5.6 NE to 5.0.4 - Smooth 
Linear Mode
