Building NAT table with fwbuilder for vmware guest
 

This is my setup, I have a host PC of OS ubuntu 7.04 and running vmware workstation. I installed Debian Linux in vmware as guest and configured exim4 as mail server and NAT networking. My ubuntu PC is already running Postfix mail server for my lab domain. I need a way (if possible) to build a NAT rule with fwbuilder on my host PC which will route all smtp request of a dynamic dns domain {somename}.homelinux.org to the vmware interface vmnet8. And my lab domain requests should remain my Postfix smtp on ubuntu.

A rough idea:
1. Destination mylab.labdomain.com 25 --> no translation(localhost receipt)
2. Destination {somename}.homelinux.org 25 --> send it to vmnet8 interface.

I have a 2MB ADSL Internet connection. I do not have a router only a modem so I use rp-pppoe on my Host PC to dial to my ISP. As of now my employer has plan to purchase a router. So, I have one Ethernet card on my PC.

Basically, I have to setup and test this Debian Server for a client who will use it for their email needs.

Any help or links will be much appreciated.

Thanks