One of the most overlooked, and least documented topics I see is the proper configuration of URLs for Proxy and Redirection. I wouldn’t worry about that little guy.” Yes, I personally like to test everything prior to making any change to the existing 2007 environment.A good article to start with is Exchange 2013 interoperability with legacy Exchange Versions by Michael Van Horenbeeck. A single Exchange 2007 server and a single Exchange 2013 server. So I usually setup some dummy URLs on the 2013 side and test all the connections (OWA, EAS, OA).The external Host Name for both 20 should be the same, (webmail.domain.com).Exchange 2007 does not support “Negotiate” authentication (See image below).
Organizations should plan how modifying the Offline Address Book (OAB) will impact network traffic.Your configuration may be different depending on how it was setup. After all testing is complete…it’s time to update the Exchange 2012/2007 URLs.