SMTP Authentication Configuration on Windows XP Professional Edition (304707)

The information in this article applies to:

Microsoft Windows XP Professional

This article was previously published under Q304707

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

SYMPTOMS

The Simple Mail Transfer Protocol (SMTP) service in Windows XP can be configured to require clients to authenticate before issuing mail commands. When you install or upgrade to Windows XP Professional in a workgroup, the NTLM (formerly called Microsoft Windows NT LAN Manager) and Generic Security Services API (GSSAPI) authentication options may not work.

CAUSE

NTLM and GSSAPI may not work if a registry key is set that forces guest-only authentication.

WORKAROUND

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 work around this issue, set the force guest authentication registry key:

Use Registry Editor to locate the following key in the registry:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa
Double-click the ForceGuest value.
In the Value Data box, type 0, and then click OK.

Modification Type:	Major	Last Reviewed:	6/11/2002
Keywords:	kbenv kbprb kbui KB304707