XCCC: Clients That Run Internet Explorer 5.0 or Later Cannot Connect to Exchange 2000 Server Through OWA

Clients that run Microsoft Internet Explorer version 5.0 or later cannot use Microsoft Outlook Web Access (OWA) to connect to your Microsoft Exchange 2000 Server.

This behavior occurs because some proxy servers do not support WWW Distributed Authoring and Versioning (WEBDAV) as defined in Request for Comment (RFC) 2518.

To resolve this problem, obtain the latest service pack for Microsoft Exchange 2000 Server. For additional information, click the following article number to view the article in the Microsoft Knowledge Base: The English version of this fix should have the following file attributes or later:

Component: OWA

File name	Version
Davex.dll	6.0.4720.6
Exprox.dll	6.0.4720.6

NOTE: Because of file dependencies, this update requires Microsoft Exchange Server 2000 Service Pack 1. After you apply this fix, you also need to add the ForceClientsDownLevel value in the registry.

WARNING: If you use Registry Editor incorrectly, you may cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that you can solve problems that result from using Registry Editor incorrectly. Use Registry Editor at your own risk.

To add the ForceClientsDownLevel value:

1.	Start Registry Editor (Regedt32.exe).
2.	Locate and click the following key in the registry: HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\MSExchangeWEB\OWA
3.	On the Edit menu, click Add Value, and then add the following registry value: Value name: ForceClientsDownLevel Data type: REG_DWORD Value data: 1
4.	Click OK.
5.	Quit Registry Editor.

To work around this problem, if clients must connect over the proxy server, disable WEBDAV on the server. If you do so, clients that run Internet Explorer 5.0 or later can use OWA.

Microsoft has confirmed that this is a problem in Microsoft Exchange 2000 Server. This problem was first corrected in Microsoft Exchange 2000 Server Service Pack 2.