exchange 2003 with Outlook2003-2007, Outlook Express on XP/Vista and Win7, and various smart phones. Need to know how to configure Exchange to authenticate with e-mail address, instead of domain\username. Everything works fine with domain\username login. I thought domain\username and e-mail address were interchangable in a default installation with POP3 enabled but MS Support says that this isn't possible and I just need to reconfigure every client with the domain\username - I am not sure if I have a problem or just lack the know-how. I need this to seamlessly move 30 POP3 users over from on-line hosting, All users already have clients configured with e-mail address. I plan to then systematically move them to a secure login method. I am also wondering if I should forget the whole POP3 setup and go straight to IMAP, SPA or some other type of secure login. Any info you can provide will help. Thanks in advance.Henry Castillo