Microsoft KB Archive/899152

= You receive an error message when you try to use Windows Messenger 5.1 or earlier to connect to a computer that is running Office Live Communications Server =

Article ID: 899152

Article Last Modified on 9/16/2005

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APPLIES TO


 * Microsoft Windows Messenger 4.0
 * Microsoft Windows Messenger 4.5
 * Microsoft Windows Messenger 4.6
 * Microsoft Windows Messenger 4.7
 * Microsoft Windows Messenger 5.0
 * Microsoft Windows Messenger 5.1

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SYMPTOMS
When you try to use Microsoft Windows Messenger to connect to a computer that is running Microsoft Office Live Communications Server, the connection does not work. Additionally, you receive the following error message:

407 Proxy Authentication Required

This symptom occurs if the following conditions are true:
 * You are running Windows Messenger version 5.1 or earlier.
 * The Microsoft Internet Security and Acceleration (ISA) Server-based proxy computer does not use Basic authentication.



CAUSE
This problem occurs because Windows Messenger 5.1 and earlier do not support proxy authentication through an ISA Server-based computer that does not use Basic authentication.



WORKAROUND
To work around this problem, configure the ISA Server-based computer to use Basic authentication.

Keywords: kberrmsg kbtshoot kbprb kbauthentication KB899152

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