There was no change in the network, actually all this happened while I was out of the country, unless if there was a hacking of some sort. Uninstalling and re-installing iptables as shown below did not help.
Code:
[root@mail conf]# /opt/zimbra/bin/zmiptables -u
[root@mail conf]# /opt/zimbra/bin/zmiptables -i
[root@mail conf]# su zimbra
[zimbra@mail conf]$ zmcontrol startup