Event ID 9646 is logged on the Exchange Server 2010 mailbox server when you access a mailbox that has more than 250 folders by using an IMAP4 client

Consider the following scenario:
  • You have a mailbox that has more than 250 folders in a Microsoft Exchange Server 2010 environment.
  • You access the mailbox by using an Internet Message Access Protocol 4 (IMAP4) client.
  • The IMAP4 client issues a SELECT command or a STATUS command for each folder.
In this scenario, you cannot see all the message items in the mailbox. Additionally, the following event is logged in the Application log on the Exchange Server 2010 mailbox server:

Log Name:      Application
Source:        MSExchangeIS
Date:          Date
Event ID:      9646
Task Category: General
Level:         Error
Keywords:      Classic
User:          N/A
Computer:      Computer
Mapi session "GUID: /o=Organization/ou= Administrative Group/cn=Recipients/cn=User" exceeded the maximum of 500 objects of type "objtMessageView".

Two objtMessageView objects are used when an IMAP4 client issues a SELECT command or a STATUS command for a folder. However, the Exchange server does not release one of the objtMessageView objects for the previous folder when the IMAP4 client issues another SELECT command or another STATUS command for a different folder. When the mailbox has more than 250 folders, the IMAP4 client exhausts the maximum number of the objtMessageView objects on the Exchange server, and this issue occurs.

To resolve this issue, install the update rollup that is described in the following article in the Microsoft Knowledge Base: 
2685289 Description of Update Rollup 3 for Exchange Server 2010 Service Pack 2

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.
For more information about IMAP4 features and commands, go to the following Microsoft website:For more information about Exchange store limits, go to the following Microsoft website:

Article ID: 2699023 - Last Review: 05/30/2012 12:10:00 - Revision: 1.1

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