Microsoft KB Archive/840183

= Outlook Web Access clients cannot open mailboxes after Software Update Services is installed on a computer that is running Exchange 2000 or Exchange 2003 =

Article ID: 840183

Article Last Modified on 10/25/2007

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APPLIES TO


 * Microsoft Exchange Server 2003 Enterprise Edition
 * Microsoft Exchange Server 2003 Standard Edition
 * Microsoft Exchange 2000 Enterprise Server
 * Microsoft Exchange 2000 Server Standard Edition

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SYMPTOMS
After you install Microsoft Software Update Services on a computer that is running Microsoft Exchange 2000 Server or Microsoft Exchange Server 2003, Microsoft Outlook Web Access (OWA) clients can connect to the Exchange 2000 server, but the Inbox may stop responding (hang). You receive the following message indefinitely in the space where the Inbox typically appears in the OWA client:

&quot;Loading...&quot;

The W3svc1.log file for Internet Information Services (IIS) may contain an error message that is similar to the following:

404 failure 

The W3svc1.log file is located in the \System32\Logfiles\ folder.



CAUSE
This problem typically occurs after you install Software Update Services on an IIS server that also runs Exchange 2000 or Exchange 2003. By default, Software Update Services locks down the IIS server in Exchange compatibility mode, but the URLScan tool is installed in dynamic Web server mode and not in Exchange compatibility mode.

Some Exchange 2000 and Exchange 2003 components cannot be used by Exchange 2000 or Exchange 2003 when the URLScan tool is locked in dynamic Web server mode. These components include Web Distributed Authoring and Versioning (WebDAV) and other Hypertext Transfer Protocols (HTTP), In this case, OWA clients that depend on these Exchange 2000 and Exchange 2003 components may not be able to access their mailboxes.

Note Microsoft recommends that you do not install Software Update Services on a computer that is running Exchange 2003, Exchange 2000, or Microsoft Exchange Server 5.5. Installing Software Update Services is supported on Microsoft Windows Small Business Server 2003.



RESOLUTION
To resolve this problem, you must install the IIS Lockdown and the URLScan Internet Information Services (IIS) security tools in Exchange compatibility mode so that Exchange 2003 and Exchange 2000 function correctly.



STATUS
This behavior is by design.



MORE INFORMATION
The URLScan tool is an Internet Server API (ISAPI) filter that screens and monitors incoming HTTP requests for Internet Information Server 4.0, Internet Information Services 5.0, and Internet Information Services 5.1 (IIS).

For additional information, visit the following Microsoft Web site:

http://www.microsoft.com/technet/security/tools/urlscan.mspx

