 Check for sendmail
I had the same problem as descibed above ... where it appeared that the MTA was starting on "zmcontrol start" -- but on "zmcontrol status" is was stopped. Somehow the Zimbra install overlooked that I had sendmail running. This was a clean install of FC3, updated using yum. I simply stopped sendmail (and took it out the startup) and was off to the races. For anyone else with the same problem, try:
ps aux | grep sendmail
if you find it, stop it:
/etc/init.d/sendmail stop
and remove it from the startup:
chkconfig sendmail off |