Internal & External IP Address

We want to redirect our email from our Exchange server to a Symantec Gateway for SMTP machine. This machine will screen all of our incoming mail and forward it on to the Exchange server. In order to do this we need to have the MX Record for DNS modified to point to the Symatec Machine. We have contacted our Internet Hosting Co. and they have identified the present MX address as being the Exchange machine. I have contacted QWest and they have told me what range of IP's we have been assigned associated with our T1....63.#.#.240-247 (241-246 usable)

1.) How can I go about determining what has been assigned to these IP's. I know the Exchange Machine has one of them assigned to it (241). Pinging the other addresses gets no response. If I use URL all of the networked systems come back with 246. I assume this has been assigned to our router. Any thoughts.

2.) How do I assign a machine (Win2000/XP) an external IP to use? The NIC's are set with the Internal IP and I'm familiar with this whirld, but I've never setup a mchine to be recognized externally.

All help is much appreciated,

This is what I did at my office:

You have to give your machine a static "internal" ip of 192.168.1.# (or 10.0.0.# or something similar) and have your router forward requests from 63.#.#.24? from the internet to the internal ip of the machine.
OR you can forward just the ports 25 and 110 to the machine serving your email. Let us know if this helps.

MICHAEL