Topic Last Modified: 2007-01-08

The Microsoft® Exchange Server Analyzer Tool reads the following registry entry to determine whether the default maximum number of open messages per MAPI session has been changed:


If the Exchange Server Analyzer finds the objtMessage registry value present and configured with any value other than 250, a non-default configuration message is displayed.

When manually added and configured, the objtMessage registry value determines the maximum number of open messages per MAPI client. By default, Exchange Server 2003 and Exchange Server 2007 limit the number of open messages to 250. When a MAPI client attempts open more than 250 messages, the following event is logged in the application event log on the Exchange Server computer that contains the client's mailbox:

Event Type: Error

Event ID: 9646

Event Source: MSExchangeIS

Event Category: General

Description: Closing Mapi session "/o= OrganizationName /ou= AdministrativeGroupName /cn=Recipients/cn= UserName " because it exceeded the maximum of 250 objects of type "objtMessage".

The objtMessage registry value represents a configuration opportunity that provides an 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 objtMessage 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 want to use the objtMessage 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" (