The Microsoft Edge Transport service (EdgeTransport.exe) may crash on a Microsoft Exchange Server 2010 Hub Transport server. Additionally, the following events are logged in the Application log:
This issue occurs because of a System.NullReferenceException exception. The Edge Transport service checks the send item configurations during message submission. However, when multiple threads access protected data at the same time, an exception is thrown and the service crashes.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.