All the Knowledge base articles are ruled out for the following reasons: (1). I am using Outlook 2000 and not 2002 (2). I do not get any authentication request after going through the usual Windows computer logon screen. In this case it's as if the name resolution process fails completely. This cannot be due to an installation problem otherwise I would also have failed to connect to the Windows 2000/Exchange 2000 test server. Thanks anyway for your suggestion, and any more would be most welcome.