This article was previously published under Q296232
IMPORTANT: This article contains information about modifying the registry. Before you modify the registry, make sure to back it up and make sure that you understand how to restore the registry if a problem occurs. For information about how to back up, restore, and edit the registry, click the following article number to view the article in the Microsoft Knowledge Base:
256986 Description of the Microsoft Windows Registry
If you use Microsoft Internet Explorer 5 or later to gain access to Microsoft Outlook Web Access (OWA), and you gain access to the Exchange 2000 server through a Netscape proxy server, OWA may display an empty Inbox that does not contain any folders (the proxy server is running Netscape Proxy Server 2.5.2 on BSDI UNIX). If you use Internet Explorer 5 or later to gain access to OWA, and you gain access to the Exchange 2000 server directly (not by means of a Netscape proxy server), OWA works correctly.
If you use Netscape Communicator 4.5.1 to gain access to OWA, and you gain access to the Exchange 2000 server through a Netscape proxy server, OWA also works correctly, although the version of OWA that is run in this case is the earlier, less capable "reach" version.
This problem can occur because Internet Explorer 5 and later and OWA use WebDAV methods like SEARCH, PROPFIND, PROPPATCH, MKCOL, MOVE, BMOVE, DELETE, BDELETE, and so on by design. Some proxy servers, including Netscape, do not support these methods.
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 resolve this problem, apply Exchange 2000 Server Service Pack 2 (SP2), and then make the following registry changes to allow Davex to process all client requests as if they are from Microsoft Internet Explorer 4.0 and earlier. For additional information about how to obtain the latest Exchange 2000 Server service pack, click the article number below to view the article in the Microsoft Knowledge Base:
301378 XGEN: How to Obtain the Latest Exchange 2000 Server Service Pack
To edit the registry to allow Davex to process all client requests as if they are Internet Explorer 4.0 and earlier:
Start Registry Editor (Regedt32.exe).
Locate and click the following key in the registry:
On the Edit menu, click Add Value, and then add thefollowing registry value:
Value name: ForceClientsDownLevel Data type: REG_DWORD Value data: 1
Quit Registry Editor.
Restart the World Wide Web Publishing Service on the Exchange 2000 computer.
The registry change takes effect immediately.
NOTE: In situations where you have implemented a front-end server, you must apply this registry change to the front-end server also. This way Exprox.dll will treat the client as if it were an Internet Explorer version 4.0 or earlier browser. Restart your Internet service after you make the change.
To work around this problem, use Secure Sockets Layer (SSL) Encryption so that the proxy or firewall server does not view the packets.
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.
This registry key was first introduced in Exchange 2000 Service Pack 1.
This problem can occur if you are using any proxy or firewall server that does not support DAV Methods.
For additional information about this problem, click the article number below to view the article in the Microsoft Knowledge Base:
301017 Users Cannot Access OWA Using Versions of IE 5.0 or Newer