An Exchange server loses its connection to domain controllers if a public folder server is down in Exchange Server 2010
Content provided by Microsoft
Applies to: Exchange Server 2010 Service Pack 3Exchange Server 2010 EnterpriseExchange Server 2010 Standard
Consider the following scenario:
You have a large Microsoft Exchange Server 2010 environment.
One or more public folder servers go down.
In this scenario, the Exchange server generates too many concurrent Active Directory queries to discover alternative public folder servers for the Microsoft Outlook client and each public logon. Then, the Exchange server loses its connection to the domain controllers because the network send queue of Lightweight Directory Access Protocol (LDAP) servers is full.
Additionally, the following event is visible in the Application log in Event Viewer:
This issue occurs because lots of Active Directory queries are generated by the Exchange server for the public folder topology when one of the public folder servers goes down.