Hi
Here are "three differnet possibilities" you can try. Please note, I have not used net2phone before, I just had a brief look at their support pages.
1. Try the SOCKS proxy (1080).
2. Map UDP port 6801 to the client machine.
3. Open UDP port 6801 to the WinGate server, place the WGIC (WinGate Internet Client) on the client machine. In the WGIC applet, set the net2phone.exe application to global.
Reference:
http://web.net2phone.com/consumer/commc ... rewall.asp
Let us know how you get on.