Some Microsoft Outlook clients connect to a Client Access server array by using a hardware load balancer in a Microsoft Exchange Server 2010 environment.
One of the Mailbox servers freezes.
In this scenario, all the threads of the RPC Client Access service (RPCClientAccess.exe) on all Client Access servers in an Active Directory site display a pending status. Eventually, the threads become exhausted. Additionally, users cannot access their mailboxes in their Outlook clients.
This issue occurs because the limit for the number of pending threads in the RPCClientAccess.exe process is not low enough. Therefore, it takes a long time to call back threads from the Mailbox server that freezes.
To resolve this issue, install the following update rollup:
2866475 Description of Update Rollup 2 for Exchange Server 2010 SP3
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about the RPC Client Access service, go to the following Microsoft website: