We have someone using PPTP to connect to our Exchange server. He is able to use the intranet without problems. He can even get into Outlook, but the troubles start there.
Outlook freezes up after it's been open or when he tries to open an attachment.
What's going on?
First check his basic connectivity to the Exchange server. Find out if he sees it when he does a NET VIEW and if he can ping it by name.
If that checks out, then examine your firewall and router configurations to make sure they're allowing RPC communications between the Outlook workstation and the Exchange server. I'm betting you'll find that you can't reliably ping your Exchange server by name from that workstation.
The quick workaround for that is to add the Exchange server's name and IP address to a HOSTS file on that workstation. The long-term solution is to get your name resolution (WINS) working properly for that workstation so it can resolve the IP address properly.