Just FYI,
There are no other running process on the server:
nmap localhost
Starting Nmap 4.20 (
Insecure.Org - Nmap Free Security Scanner, Tools & Hacking resources ) at 2009-11-18 00:09 EST
Interesting ports on localhost.localdomain (127.0.0.1):
Not shown: 1694 closed ports
PORT STATE SERVICE
22/tcp open ssh
53/tcp open domain
953/tcp open rndc
I configured Zimbra webmail to port 81 (because I'm running Apache Web Server with mod_proxy). We need this to host other website. This setup worked well ever since we started using 4.x and 5.x.
Just one more info, I stopped Apache while I ran install.sh so the port conflict checker will not report any error.