DOCUMENT:Q167752  12-MAY-1999  [exchange]
TITLE   :XWEB: Web Client Fails with NTLM
PRODUCT :Microsoft Exchange
PROD/VER:WinNT:5.0,5.5
OPER/SYS:
KEYWORDS:kbusage

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The information in this article applies to:

 - Microsoft Outlook Web Access, version 5.5 
 - Microsoft Exchange Active Server Components, version 5.0 
 - Microsoft Exchange Server, versions 5.0, 5.5 
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SYMPTOMS
========

When you use an Internet browser to connect to a mailbox on an Exchange Server
computer configured for Windows NT Challenge/Response (NTLM) password
authentication, the following error message may appear:

   Internet Explorer cannot open the Internet site
   http:///logonfrm.asp?mailbox=
   An unexpected error has occurred. Restart Internet explorer and then try
   again.

CAUSE
=====

The Microsoft Exchange Windows 95 client and Web client currently require that
the Microsoft Client for Microsoft Networks redirector (Vredir.vxd) be installed
on the Windows 95 client. Because Microsoft Exchange uses integrated security
with the Windows NT Directory Services, the Microsoft Exchange client needs
validation from a Windows NT domain controller. For NetWare-only environments
using Microsoft Exchange Server, this means both the Microsoft Network
redirector and a NetWare redirector must be installed on a Windows 95 client.

This limitation is a result of the way the NTLM security subsystem was designed
on Windows 95 and is not a limitation of the Microsoft Exchange Windows 95
client. The Microsoft Exchange Windows 3.x and Microsoft Exchange Windows NT
clients do not have this requirement.

WORKAROUND
==========

An updated NTLM security DLL fixes this problem so that the Microsoft redirector
is no longer needed for the Exchange client to get validated. It should be
placed in the Windows\System subdirectory. This updated DLL is found in the
Windows 95 DCOM update on:

   http://www.microsoft.com/com/dcom/dcom95/dcom1_3.asp


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Keywords          : kbusage 
Technology        : kbOutlookSearch kbZNotKeyword6 kbExchangeSearch kbExchange500 kbExchange550 kbZNotKeyword2 kbOWASearch kbOWA550 kbExchangeActiveServComp500
Version           : WinNT:5.0,5.5

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