I recently upgraded to Internet Explorer 11 and noticed that I could only get to the light version of OWA on my Microsoft Exchange 2010 box. The box was checked and greyed out with no option to uncheck it.
This happens because Exchange determines which version of OWA to use based on the browser that you use. A browser makes itself known to the web server via a “User Agent String”. Due to changes in the User Agent String of Internet Explorer 11 (on both Windows 7 and Windows 8), Exchange doesn’t recognize the browser and serves the light version of OWA.
-Exchange 2013 CU3
-Exchange 2010 SP3 RU3
-Exchange 2007 RU12
-Exchange 2003 ... no deal!
If your organization isn't ready to install the update for Exchange, then you can enable Compatibility View in IE 11 for the OWA website by doing the following:
1) In IE 11, click on 'Tools' and choose 'Compatibility View Settings'.
2) In the dialog pop-up, you’ll see the root domain hosting the OWA website.
3) Click 'Add' and 'Close' and the logon page will automatically refresh with the light option available and not selected.