I have a Windows 2k3 SBS sitting behind a SonicWall. Our users connect using the windows PPTP VPN. When connecting, the VPN connection connects quickly and without issue. However, when the VPN connection is active, Outlook hangs. It will give either the message that its trying to connect to exchange or waiting to update this folder and the icon will indicate "Outlook is requesting data from the server".
Alternatively, with out connecting on the VPN, I can get to OWA fine and the mail to our blackberries all sync with out issue. In addition, I can remote desktop to the server external address fine.
While connected on the VPN, I can watch the traffic on the connection and there never seems to be much activity. Also, while connected I can ping the server internal IP as well as the server hostname.