Setup OWA authentication methods in exchange 2007/2010.In exchange 2010 and 2007, exchange gave you the option of multiple methods of loggin into owa here is how to setup these owa authentication methods. Username only or full domain and username and UPN
On a fresh Exhange 2013 install you cannot log into the ECP/EAC and receive the error Server Error in ‘/owa’ Application. The Active Directory user wasn’t found.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.