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NSPI connections to a Windows 2008-based domain controller may cause MAPI client applications to fail with an error code: "MAPI_E_LOGON_FAILED"
Article ID: 949469 - View products that this article applies to.
Important This article contains information about how to modify the registry. Make sure that you back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/322756/ )How to back up and restore the registry in Windows
A Name Service Provider Interface (NSPI) connection from a MAPI client to a Windows Server 2008-based domain controller may fail with the following error code that is returned from the server:
In some instances, a credential dialog box may appear in the MAPI client user interface when you encounter this issue.
Affected clients include Microsoft Outlook and BlackBerry Enterprise Server.
This behavior occurs because Windows Server 2008 only allows for a default maximum of 50 concurrent NSPI connections per user to any domain controller. Additional NSPI connections are rejected with a MAPI_E_LOGON_FAILED error code.
Note Windows Server 2003 and earlier versions of Microsoft Windows operating systems do not exhibit this behavior. The change of behavior in Windows Server 2008 is intended to protect domain controllers against clients that open too many NSPI connections without then closing the connections. Too many connections such as these can result in resource depletion.
To resolve this issue, check all NSPI connections that processes on the client create for connection leaks. For example, a call to the NspiBind function must have a corresponding call to the NspiUnbind function when an NSPI connection is no longer required. This operation may require that you debug any custom scripts or applications that are using NSPI. If this issue affects external applications, contact the software vendors for updates.
Note The Outlook NSPI MAPI provider that is installed with Microsoft Outlook is only intended for use with Microsoft Outlook. External scripts and applications that rely on the Outlook NSPI MAPI provider are not supported.
How to modify the registry to allow for additional NSPI connectionsWarning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.
If more concurrent NSPI connections per user are legitimately required, you can change the default limit. To do this, follow these steps:
Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.
To confirm that you encountered the issue that is described in the "Symptoms" section, follow these steps:
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For more information, click the following article number to view the article in the Microsoft Knowledge Base:
(http://support.microsoft.com/kb/314980/ )How to configure Active Directory diagnostic event logging in Windows Server 2003 and in Windows 2000 Server
Article ID: 949469 - Last Review: October 9, 2011 - Revision: 11.0