Here are some posts related to Zimbra mail server's ports and configuration:

Prepare the VPS

Before we install Zimbra, we must install the follow packages

root@HN# vzctl exec 101 yum install ant sysstat gmp compat-libstdc++-296 compat-libstdc++-33

The above list should be good enough for Zimbra 6. If installing Zimbra 5, then we also have to have: