WinProxy IP settings.

WinProxy adapters:

set the external adapter to 172.16.1.1
- set its gateway to 172.16.1.2
set the internal adapter to 10.0.0.1
- do not use a gateway setting on the internal adapter

DNS:

Mail Servers:

if the firewall contains a mail server, set WinProxy's mail protocol IP to 172.16.1.2.
if you have an internal mail server elsewhere on the network, use the 'incoming smtp' setting in WinProxy's mail protocol settings to forward incoming mail to the machine on your network, and put the IP address of that machine in WinProxy's mail protocol settings.
if you use a mail server outside of your local network, set WinProxy's mail protocol to the names of those servers.