You install Microsoft Windows Server 2003 Service Pack 1 (SP1) on a server cluster. The server cluster is running a clustered Microsoft Exchange Server 2003 back-end server. You experience the following symptoms:

•	If a user tries to access a mailbox by using Microsoft Outlook Web Access, that user receives the following error message: 500 - Internal server error
•	If a user tries to access a mailbox by using Microsoft Outlook Web Access, that user receives the following error message: Service Unavailable They receive the same message if they browse the Exchange virtual server or the Exchange virtual directory.
•	If you log on to a client computer by using administrator rights and then try to access a mailbox by using Outlook Web Access, you are successful.

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This problem is caused by some of the security enhancements that are included with Windows Server 2003 SP1.

In this scenario, when a user tries to access a mailbox by using Outlook Web Access, HTTP requests into the clustering API by impersonating the logged-on user. However, there have been security changes in Windows Server 2003 SP1. The security restrictions for the APIs that perform remote registry access have been changed. Therefore, the logon attempt is not successful.

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Update information

The following file is available for download from the Microsoft Download Center:

Download the Exchange 2003-KB841561-v2-enu package now. (http://www.microsoft.com/downloads/details.aspx?FamilyId=050BE883-11FC-4045-B988-C737E79C65D0&displaylang=en)

Release Date: April 1, 2005

For more information about how to download Microsoft Support files, click the following article number to view the article in the Microsoft Knowledge Base: Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to the file.

Prerequisites

Because of file dependencies, you must have Exchange Server 2003 Service Pack 1 (SP1) installed to apply this hotfix. For more information, click the following article number to view the article in the Microsoft Knowledge Base:

Restart requirement

You must restart your computer after you apply this update.

Update replacement information

This update does not replace any other updates.

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time tool in Control Panel.

   Date         Time   Version            Size    File name
   --------------------------------------------------------------
   03-Jun-2004  06:01  6.5.7232.0      1,086,464  Davex.dll      

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Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

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For more information, click the following article numbers to view the articles in the Microsoft Knowledge Base:

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