i have a user with XP SP2-2gig of RAM, Outlook 2k3 SP2. this is his home computer that connects to our exchange server via a Cisco VPN tunnel. His outlook is set up with a MAPI profile that does not use cached mode. Outlook performs normally at all times except when he is not using the client for several hours. upon sending the first message outlook hangs for several seconds and he receives the message "outlook is trying to retrieve data from the microsoft exchange server: <servername>" the message will finally send and outlook will again function normally until he is away. I have tested his local PC and it does not have any such problem. This PC has functioned without this problem in the past and I'm not sure what changed to cause this. i am currently running network monitor to see if i can narrow down what is going on. does any one have any other suggestions?

That particular response from Outlook when trying to get data from Exchange is called an RPC Cancel Request dialogue. It is really a non-specific error that can be a challenge to troubleshoot. With the VPN, I suspect it is just taking a little too long for all the components to be reached and for a message to send. Name resolution slowness or Active Directory performance may contribute to this problem as well. You might try a hosts file entry for the Exchange server for the VPN clients. If the VPN is strictly for Outlook connectivity, you might consider RPC/HTTPS as an alternative.

As a general methodology for troubleshooting those RPC cancel requests, there is a kb article 839862: http://support.microsoft.com/?id=839862. I imagine the VPN is really the contributor here though, as you have proven connectivity without it.