I am in the process of installing a new Exchange 2010 server with CAS/HUB/MB roles installed on it. This server is published behind a Forefront TMG server. The old server which is an Exchange2007 server with CAS/HUB/MB which is just behind an ASA at the moment and not published to the TMG.
When I switch everything on my router to point all incoming traffic to the TMG server I can get OWA to come up and login to a new account that I created on the Exchange box, If I attempt to access an account still loaded on the Exchange 2007 box I receive the following error "a server configuration change is temporarily preventing access to your account. Please close all internet explorer windows and try again in a few minutes. if the problem continues, contact your helpdesk."
After doing some research is the only way to fix this by changing the external URL that the old legacy server is using to say from mail.domain.com to something new like legacy.domain.com? Could I publish anything on my TMG server to get this to work without changing the external URL?
Thanks for your time and suggestions.