Microsoft KB Archive/265256

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XWEB: Windows 2000 Users Are Unable to Gain Access to Outlook Web Access

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Q265256

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The information in this article applies to:


 * Microsoft Exchange Server, version 5.5
 * the operating system: Microsoft Windows 2000 SP1

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SYMPTOMS
When a user attempts to log on to Outlook Web Access (OWA) from a computer that is running Windows 2000 Server or Windows 2000 Professional, the user may be prompted for credentials three times, and then one of the following is displayed:


 * A blank page
 * The following error message:

Users who log on to OWA from a computer that is running any other Microsoft Windows operating system can gain access to OWA without being prompted.

CAUSE
This issue can occur if OWA is installed on a computer that is running Windows 2000 Server with Integrated Windows Authentication enabled as one of the authentication methods on the Exchange Server virtual directory.

RESOLUTION
To resolve this issue, edit the Constant.inc file that is located in the Exchsrvr\Webdata\Usa folder on the server on which OWA is installed:


 * 1) Use Notepad to open the Constant.inc file.
 * 2) Under '--Other Strings--', locate the following line:
 * 3) Change the entry to read as follows:
 * 4) On the File menu, click Save.
 * 5) On the File menu, click Exit.

MORE INFORMATION
When you use a computer that is running either Windows 2000 Server and Internet Explorer 5.0 or Windows 2000 Professional and Internet Explorer 5.0 to attempt to log on to Internet Information Service (IIS) 5.0 and Integrated Windows Authentication is enabled, a negotiation is performed to determine whether the Kerberos protocol or Windows NT Challenge/Response will be used for authentication.

When you use a computer that is running either Windows 2000 Server and Internet Explorer 5.0 or Windows 2000 Professional and Internet Explorer 5.0, the server variable AUTH_TYPE is set to Negotiate. When you use a computer that is running any other Windows operating system, the server variable is set to NTLM. OWA checks what this variable returns against the bstrAuthTypesAccepted value that is modified to ensure that the authentication type is acceptable before OWA allows a user to log on.

Additional query words: :blank screen blank white internet explorer ntlm three-field prompt

Keywords : exc55

Issue type : kbprb

Technology : kbOSWin2000 kbOSWinSearch kbExchangeSearch kbExchange550 kbZNotKeyword2 kbOSWin2000SP1