If you haven't already used these free Microsoft Online tools please give them a try. I find them indispensible when troubleshooting issues or setting up new Exchange or OCS environments that require external network user connectivity.
Since these tools require actual user accounts to authenticate against the target environment I would strongly suggest you use test user accounts that you can disable once you are completed your testing.
There is a test both for Exchange 2007 and Office Communications Server 2007.
https://www.testexchangeconnectivity.com/
https://www.testocsconnectivity.com/
Excellent! Very convinient for OCS accounts.
Posted by: Account Deleted | November 03, 2009 at 08:19 AM