The event log resembles the following:
Log Name: Application
Source: MSExchange Common
Event ID: 4999
Task Category: General
Watson report about to be sent for process id: Process ID, with parameters: E12, Type, Version Number, WS, unknown, M.E.S.C.E.EwsHttpResponseWireWriter.InternalEndSendResponse, System.NullReferenceException, dda, unknown.
This issue occurs because a third-party product disconnects in an unexpected state. This disconnection causes a System.NullReferenceException exception, and that triggers the crash.
To resolve this issue, install Update Rollup 10 for Exchange Server 2010 Service Pack 3.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.