2 users same PC

Am using Outlook 2000, NT 4 (sp 6) and Exchange 5.5 Have been trying to set up 2 users on the same PC. Set up two profiles in the Control Panel. Both users have identical setup in Exchange Administrator. Both have identical permissions in Outlook. Only one user is able to receive external email. Both can send. Both work internally sending and receiving. It must be something simple. What am I forgetting?