We have a L2L VPN tunnel that keeps going down – our Exchange 2010 Server is hosted across the tunnel. I am wondering how to force Outlook 2007 to connect via HTTP or HTTPS to the Exchange Server at all times so that this is never an issue. The Exchange server is exposed to the Internet on ports 25, 80, and 443. OWA works when the L2L tunnel is down.
Note that I have already done the "Fast, Slow connections use OWA" trick.
Best Answer
Go to Tools->Account Settings
Click on the E-mail tab. Click "Change E-mail account".
Click "More Settings". Click on the "Connection" tab. Click "Exchange Proxy Settings". Make sure "On fast networks, connect using HTTP first, then connect using TCP/IP" is checked, as well as "On slow networks, connect using HTTP first, then connect using TCP/IP".
That will force Outlook Anywhere over traditional MAPI.
EDIT
As noted below - if you're using a self signed cert, Outlook Anywhere will almost never work. You'll want to use a third party CA to secure communications. Use www.testexchangeconnectivity.com to troubleshoot Outlook Anywhere issues - if it doesn't work there, it's not likely to on your client machines.