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Outlook Continues to Prompt You for Logon Credentials
Article ID: 312630 - View products that this article applies to.
This article was previously published under Q312630
NoticeThis article applies to Windows 2000. Support for Windows 2000 ends on July 13, 2010. The Windows 2000 End-of-Support Solution Center
(http://support.microsoft.com/?scid=http%3a%2f%2fsupport.microsoft.com%2fwin2000)is a starting point for planning your migration strategy from Windows 2000. For more information see the Microsoft Support Lifecycle Policy
When you use Outlook to try to connect to a Microsoft Exchange server, you may be prompted to provide a user name, password, and domain name. However, after you provide this information, Outlook may repeatedly prompt you to provide your credentials again. Other related symptoms may include the inability to connect to Microsoft Outlook Web Access (OWA) by using the IP address of the server. If you are unable to connect by using the IP address of the server, the Microsoft Internet Information Server (IIS) computer may prompt you for credentials, and you may receive the following error message when these credentials do not work:
401.1 Unauthorized: Logon Failed.
This behavior may occur if the server is configured to only accept Microsoft Windows NT LAN Manager (NTLM) version 2 and reject NTLM and LM, and the Outlook client computer is not configured with the same LAN Manager authentication level.
To verify and correct this behavior, find the proper location where you can change the LAN Manager authentication level to set the client and the server to the same level. For example, you may have to look on the domain controller, or at the domain controller's policies.
Check the Domain ControllerNOTE: You may have to repeat the following procedure on all domain controllers.
Check the Domain Controller's Policies
Because client computers that are running any of the following operating system are not affected by Windows 2000 Group Policy objects, you may have to manually configure these clients:
(http://support.microsoft.com/kb/239869/EN-US/ )How to Enable NTLM 2 Authentication
(http://support.microsoft.com/kb/241338/EN-US/ )Windows NT LAN Manager Version 3 Client with First Logon Prevents Subsequent Logon Activity