Firewall Configuration

Trying to decide what the best way is to configure my firewall and I
would appreciate anyone's input into this
Here is what I have now
Two NT 4 File Servers in my local domain using private IP Range of
192.17.9.1 - 255
I have a NT 4 Workstation loaded with Proxy with two network adapters
I use a program called Avirt Gateway suite which gives me internal
email server and a proxy for getting on the internet
I connect to Genuity's frame relay via a Cisco router IP Range of
x.x.x.101 - 255

I just purchased a SoncWall Pro 200 Firewall
It has three ports on the back of it
One connection to the lan
One Connection to the WAN
And one connection to a DMZ

One of my NT4 Servers is running DHCP

Do I even need the Proxy Server any longer?
I need it to handle my internal Email but Genuity handles all my
external email

I have a NT 2000 Server (just a member server) that use to be my
personal workstation that I would like to fit in somewhere so I can
run Microsoft SUS

The Sonicwall supports DHCP and NAT
What I would like to do is move the internal mail server to the NT
2000 Box

Thoughts Everyone?

Thanks a bunch

James Piper
Meco Inc
Paris, IL 61944