Symptoms
When you try to log on to Outlook Web App or Exchange Control Panel (ECP), you receive the following error message:
Sorry, something went wrongAn error has occurred on the server.TECHNICAL DETAILS
If you click the TECHNICAL DETAILS link, the following text is displayed:
An unexpected error occurred and your request couldn't be handled.X-OWA-Error: System.NullReferenceExceptionX-OWA-Version: OWA VersionX-FEServer: Exchange 2013 Client Access ServerX-BEServer: Exchange 2013 Mailbox ServerDate: Date and TimeNote This behavior occurs even though you can still use Microsoft Outlook to send and receive email messages.
Cause
The GUID value is stored in the browser cookie collection and is included in an Outlook Web App or ECP request. If the GUID value that's stored in Active Directory Domain Services (AD DS) doesn't match, the server blocks the request.
Resolution
To fix this issue, install Cumulative Update 11 or a later cumulative update for Exchange Server 2013.Note This update enables periodic recycle of the Outlook Web App or ECP app pools (every 14 days). If you disable this recycle functionality or set the period to more than 28 days, the issue may recur.
Status
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
More Information
When this issue occurs, the Application log in Event Viewer may show the following events:
