Microsoft Outlook Web Access (OWA) can provide Web browser-based access to Exchange 2000 Server mailbox data. However, common network and configuration problems can keep users from logging on and using OWA. This white paper includes information and advice about isolating problems and solving common errors, troubleshooting methods, administrative practices, and useful tools.

http://www.microsoft.com/exchange/techinfo/administration/2000/owatroubleshoot.asp