"Mail over Shared connection"

I have a small home network with a PIV -Windows XP Pro - and a Cablemodem connection shared to several Windows ME computers. Internet works pretty fine, but Email is my nightmare. I cant' get any email message with Outlook Express or Microsoft Outlook on the client computers... I have tried different configurations, but none of them works. It starts good, outlook contacts the server, sign me in, check the # of messages and start to download them. But that is as far as I get, because not a single message gets through. On the "server" machine it all works fine.

Any ideas?

Thanks,

Alex.