XP client on Win2000/MSProxy 2

I attached 2 XP machines via a Linksys wireless router configured as a access point to a Win 2000 LAN with MS Proxy Server 2.0. Every thing works except email on the XP boxes. I get "Host not found" with Outlook and Outlook Express.One machine has the Proxy client on it - the other no. Windows 2000 Pro and Win98 machines configured in identical manner are able to resolve email hosts. The email server in question is outside the network (internet).
What am I missing?
TIA,
Jim

 

Are the proper port open and forwarded in ap.