FYI, the AD and exchange 2003 reside in the same domain, both are installed in win2k server. For OWA 2003, how do exchange authenticates the user to AD ? let's say, user credentials are sent to exchange 2003 (by basic authentication). How does exchange authenticate te user to AD ? Is it possible to have the following flow: https --> exchange 2003 -- kerberos --> AD ? If yes, what are the settings needed ? delegation ? If it's not possible to have the above flow for AD, is it possible for non-form based auth ? thanks