This article was previously published under Q274359
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POP3/IMAP clients are not authenticated correctly if your Microsoft Exchange-based server (which is also a domain controller) is configured to use NTLM version 2 authentication and the LmCompatibilityLevel setting is set to 5.
When the LogonUser function is called with LOGON32_LOGON_NETWORK, the function does not work if the LmCompatibilityLevel setting is set to 5.
Setting the LmCompatibilityLevel setting to anything other than 5 works correctly.
To resolve this problem, obtain the latest service pack for Windows 2000. For additional information, click the following article number to view the article in theMicrosoft Knowledge Base:
260910 How to Obtain the Latest Windows 2000 Service Pack
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