Choose type 'Exchange', and enter your email address, and a nonsense password, click Create account.Here, iCal is the relief, it seems to be more tolerant: Here, it gets difficult because in the accounts wizard of OSX you do not get the chance to enter the server name (sth. However, I have a case here where autodiscover does not work (a certificate error is returned when setting up the account, obviously because the domain is not fully delegated to MS on the internal DNS servers of the previous provider). You just need to add an Exchange account in the OSX system settings at 'mail, contacts, calendar' - really simple! This should work with the native OSX apps (iCal, Mail, Address book) on Lion!
