Here’s the problem – you have a TMG firewall that was released around 2010. You had Exchange 2010 and everything was cool. Now you have Exchange 2013 and things aren’t quite as cool since the TMG firewall was never upgraded to support all the new and amazing things you get from Exchange 2013. Now what? In this article Richard Hicks will show you how to configure your aging TMG firewall to support Exchange 2013.
Check it out at:
http://www.isaserver.org/articles-tutorials/configuration-general/publishing-exchange-2013-outlook-web-app-forefront-threat-management-gateway-tmg-2010.html
HTH,
Deb