.If you need to find out how long ago it has been since a user has logged onto your network then you can do this with a command in powershell. Follow this guide.Find out how long it has been since a user logged in.
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.