User can only get mail by pressing F5

I have a user who is using Microsoft Outlook 2000 in an Exchange 5.5/NT SP6a+ environment. Initially he was using Outlook 97 when this problem started. Upgrading to Outlook 2000 was one of the attempts to repair his situation. This users mail no longer automatically comes into his mailbox. I have checked his network connections state and it is set to automatically detect. I have also made sure he is not on the remote transport function. Also I have Outlook checked so it is supposed to bring in his mail automatically. For whatever reason we cannot get his mail to come in automatically. He must press the F5 key to initiate a manual send and receive command.

Any ideas of how to fix this, or what I may be missing. Thanks to all whoreply.