ou get an HTTP 500 error attempting to access OWA on an SBS 2011 server, after you have provided your credentials to the login form.
The Microsoft Exchange Forms-Based Authentication (MSExchangeFBA) service is stopped.
Start the MSExchangeFBA service.
Article ID: 2517253 - Last Review: Mar 18, 2011 - Revision: 1
Windows Small Business Server 2011 Premium Add-On, Windows Small Business Server 2011 Standard