When you fill in your credentials on the login screen of Outlook Web Access or OWA (2010) and click submit you receive an Internal Server Error 500 and the URL shows /owa/auth.owa
There are no events logged in Application or System log that explain this problem.
IISreset does not help.
The problem and solution could be very simple.
Check the the service “Microsoft Exchange Forms-Based Authentication service” is started. If not, start the service and try to login to OWA again. Problem should be solved.
If the service doesn’t start or fails frequently you’ll have to investigate that further.
The solution is simple. Enable compatibility mode for the webpage (press alt to show the menu, look under tools).
If you want this done automatically for all your visitors you can also add a header on your IIS6 so that every viewer gets forced in Internet Explorer 8 compatibility mode. On your server open IIS manager, click the plus sign under default website and then select “Exchange” and right click and choose properties. Go to the TAB HTTP-HEADERS and add a customer header X-UA-Compatible with value IE=EmulateIE8.
Now the browser receives this header and automatically uses compatibility mode.