Consider the following scenario:

  • You install Update Rollup 4 for Microsoft Exchange Server 2010 SP2 in an environment that is running against a Blackberry Enterprise Server (BES).

  • The BES uses MAPI or Collaborative Data Objects (CDO) instead of Exchange Web Services (EWS) to communicate with Exchange servers.

  • A mailbox on a Blackberry mobile device contains many folders. For example, the mailbox contains more than 5000 folders.

In this scenario, you encounter one or more of the following issues:

  • Email message delivery to the mailbox on a BlackBerry mobile device is delayed.

  • It takes longer than expected to scan a folder hierarchy in the mailbox. For example, before you install Update Rollup 4 for Exchange Server 2010 SP2, a scan of a folder hierarchy takes about 5 minutes. After you install Update Rollup 4 for Exchange Server 2010 SP2, a scan of a folder hierarchy takes about 30 minutes to 1 hour.

  • The Microsoft Exchange Information Store process (Store.exe) on the Exchange Mailbox server uses excessive CPU resources.

  • Some BES event log entries are logged on the Exchange Mailbox server. Before you install Update Rollup 4 for Exchange Server 2010 SP2, few entries are logged, or no entries are logged.

  • Some events are logged in the BlackBerry Messaging Agent (MAGT) log. These events resemble the "Busy Working" threads that are described in the following article in the BlackBerry Knowledge Base:

    Users may experience delayed email after upgrading to Microsoft Exchange 2010 SP2 Rollup 4 or Microsoft Exchange 2010 SP2 Rollup 5


This issue occurs because the Exchange server creates a new admin session every time that the server tries to bind the delegate to each folder and retrieve folder properties for the delegate. Additionally, because the server sets a certain flag for each folder bind, a high-cost process flow occurs. Therefore, when BES requests the properties of many folders, the issue that is described in the "Symptoms" section occurs.


To resolve this issue, install the following update rollup:

2746164 Description of Update Rollup 6 for Exchange Server 2010 Service Pack 2  

To reduce the effect of this issue, use the following methods:

Method 1

Install Exchange Server SP2 RU 6 when it becomes available.

Method 2

If there are less than 15 agents on the BES, add more agents to the BES. The maximum number of agents is 15. 

Method 3

Reduce the number of folders in the mailbox.

Method 4

If the mailbox contains many folders (for example, more than 500 folders), move the mailbox to its own instance of BESAgent.exe.


Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

More Information

For more information about the issue, click the following article numbers to view the articles in the Microsoft Knowledge Base:

2726897 Admin sessions are exhausted as a result of delegate access in an Exchange Server 2010 environment

2706690 Description of Update Rollup 4 for Exchange Server 2010 Service Pack 2
The third-party products that this article discusses are manufactured by companies that are independent of Microsoft. Microsoft makes no warranty, implied or otherwise, about the performance or reliability of these products.

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