Maximum attachment per message submission 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 attachments per message submission has been changed:


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


Entry Exchange Server 2003 RTM Default Value Exchange Server 2003 SP1 and Later Default value Exchange Server 2007 Default Value





When manually added and configured, the objtAttachment registry value determines the maximum number of attachments per message submission per MAPI client. When a MAPI client attempts to send a message with more than the allowed number of attachments, the following event is logged in the application event log on the Exchange Server computer that contains 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 xxx objects of type "objtAttachment".

The objtAttachment 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.

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

  2. Navigate to:


  3. Delete the objtAttachment registry value.

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

Alternatively, if you wish to make use of the objtAttachment 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" (