Assume that you have some Active Directory sites in a Microsoft Exchange Server 2010 environment. You add some Microsoft Exchange servers, in particular, Client Access Servers that have OWA virtual directories configured. In this situation, the following events may be logged: Additionally, event ID 2084 and event ID 1216 may be logged too. These events may cause Exchange to lose its connection with all in-site domain controllers. Then, Exchange may use domain controllers in other sites. In this situation, client users cannot connect to Exchange.
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.