Simply put I would like to create multiple zimbra servers that will be conneted to one internet connection (A Single t1 line conneted to a single router). So the router is, Zimbra Server A, Zimbra Server B, Zimbra Server C

My problem is that we need to forward port 25 which I can do only once per router ( So if I forward port 25 to Zimbra Server A what do I do to accomodate port forwarding for Zimbra Server B and Zimbra Server C, etc. I realize that one solution would be to put each on different ports and use a mail port forwarding service such as dyndns.org for $45.00 each server each year. (This would at least allow 6 servers since there are only 6 ports that they will allow you to forward to you mail server).

Any ideas how to accomplish this for free??

I am a newbie so please be kind