OS X: Cannot Change Email Account Details
When adding an email account in OS X, the system prompts for your name and email address and then populates the remaining details (servers etc) as far as possible. However if the details need to be changed, there is no option to do so. For example, OS X may pick the account as being an IMAP account but it is really a POP account.
To obtain a dialog which allows the entry of manually-provided server details, press Option while choosing Continue instead of just Continue.