Consider the following scenario:
You deploy some public folder databases in a Microsoft Exchange Server 2010 environment that has Update Rollup 5 version 2 for Exchange Server 2010 Service Pack 2 (SP2) or a later-version update rollup installed.
The environment contains multiple Active Directory sites.
The default public folder server is unavailable. So, the Microsoft Exchange RPC Client Access service tries to connect to other public folder servers.
In this scenario, the Microsoft.Exchange.RpcClientAccess.Service.exe process consumes excessive CPU resources on one or more Client Access servers in the site. Additionally, Microsoft Outlook clients cannot connect to Exchange servers, or they encounter slow performance when they connect to Exchange servers.
This issue occurs because a non-optimized algorithm is used to search for other public folder servers when the default public folder server is not available or is down.
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, click the following article numbers to view the articles in the Microsoft Knowledge Base:
2750847 An Exchange Server 2010 user unexpectedly uses a public folder server that is located far away or on a slow network
2785908 Description of Update Rollup 5 version 2 for Exchange Server 2010 Service Pack 2