Well, they should be set correctly but you are getting an error saying it can't find the server and we use DNS.
What does the following return (run on the Zimbra server):
Code:
host `hostname`
dig yourdomain any
dig yourdomain mx
Also post the details of your /etc/hosts file. I assume that you have disabled any firewall or SELinux on this server?
Maybe the problem is that it takes a long time to look-up your domain? Look at this
report - that took 161 seconds (when I ran it) and that's far too long.