Last night I did an upgraded my Exchange Server 2003 Standard to Exchange Server 2003 Enterprise. Following the upgrade everything appeared fine. But today we noticed that Outlook (2007/2010) is prompting for the password to the Exchange server. The issue does not occur using OWA. I am not using RPC/HTTP. I reinstalled SP2. The really interesting part is that if we cancel the password box and hit send and receive the status changes back to Connected to Microsoft Exchange. All users are local network users and Exchange is not actually sending any mail. It is strictly used for mail/calendar storage and sharing.