I am running into an intermittent issue, where random Outlook 2007 clients will stop receiving emails even though Outlook shows as connected. I have tried using Send/Receive, re-installing Office/Outlook, Disabling Cached Mode, and the only thing that seems to work even temporarily is to close and re-open Outlook. I have reviewed both the server and client event logs, and see nothing even remotely related. These are local users, and RPC over HTTP is not configured. I have also verified that there are no problems connecting to the PDC or Exchange server via DCDIAG and NETDIAG. Network bandwidth also verified, Gigabit backbone and 100MB to the desktop with no more than 10% utilization on any given port, which is on a server running a specific network intensive application. Users running this application have no problem so I think I can exclude that piece from the overall issue.
Exchange consists of a Windows 2003 Enterprise server running Exchange 2003 PLENTY of RAM, HD and Proc for the number of users.
Clients are running WinXP SP3, and Outlook 2007 primarily.