Maximum open folder objects per logon has been changed

[This topic is intended to address a specific issue called out by the Exchange Server Analyzer Tool. You should apply it only to systems that have had the Exchange Server Analyzer Tool run against them and are experiencing that specific issue. The Exchange Server Analyzer Tool, available as a free download, remotely collects configuration data from each server in the topology and automatically analyzes the data. The resulting report details important configuration issues, potential problems, and nondefault product settings. By following these recommendations, you can achieve better performance, scalability, reliability, and uptime. For more information about the tool or to download the latest versions, see "Microsoft Exchange Analyzers" at]  

Topic Last Modified: 2007-01-08

The Microsoft® Exchange Server Analyzer Tool reads the following registry entry to determine if the default maximum number of folders that can be opened per MAPI session has been changed:


If the Exchange Server Analyzer finds the objtFolder registry value present and configured with any value other than 500, a non-default configuration message is displayed.

When manually added and configured, the objtFolder registry value determines the maximum number of folders that can be opened per MAPI client. By default, Exchange Server 2003 and Exchange Server 2007 limit the number of open folders to 500. When a MAPI client attempts to open more than 500 folders, the following event is logged in the application event log on the Exchange Server computer containing the client's mailbox:

Event Type:


Event ID:


Event Source:


Event Category:



Closing Mapi session "/o=OrganizationName/ou=AdministrativeGroupName/cn=Recipients/cn=UserName" because it exceeded the maximum of 500 objects of type "objtFolder".

The objtFolder registry value represents a configuration opportunity that provides the administrator with a greater level of control over the Exchange Server resources used by MAPI clients.


This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore the registry if a problem occurs. For information about how to restore the registry, view the "Restore the Registry" Help topic in Regedit.exe or Regedt32.exe.

To revert to the default configuration

  1. Open a registry editor, such as Regedit.exe or Regedt32.exe.

  2. Navigate to:


  3. Delete the objtFolder registry value.

  4. Close the registry editor and restart the Microsoft Exchange Information Store service for the change to take effect.

  5. Alternatively, if you wish to make use of the objtFolder registry value, instead of deleting it, keep it set to its existing value or adjust it as needed.

Before you edit the registry, and for information about how to edit the registry, see the Microsoft Knowledge Base article 256986, "Description of the Microsoft Windows Registry" (

For more information, see the Knowledge Base article 830829, "Your Exchange Server 2003 computer may stop responding after a MAPI client opens more than the default value of certain server objects" (