I need something I can talk smtp to for when the user clicks "I lost my password" and the system needs to send an automated email to let them reset it. How I get such a mail server and how it knows how to find other mail servers to send stuff on to is a black hole to me.
The other use case is I'd like to have a mailbox for each website like whippingboy@bandwidthwaste.com that I can get mail from via Mail.app using IMAP every now and then (POP would be tolerable as well but I prefer IMAP). I reckon I'll have about 20 email identities (which some day if all goes well I'll give to underlings).
I don't really want to check 20 different web pages for site specific email.
I have no intention of providing mailboxes to j random users.