- Postfix: Your mail can now have the distinction of being deleted by 53 individual subservers * Sendmail: Priority treatment if you can write, while holding down your Shift key, an m4 macro to calculate the airspeed velicoty of an unladen swallow. All other messages will be summarily deleted in 6-8 weeks, or whenever the queue daemon catches up, whichever is later * Exim: Conveniently marks every message as "unrouteable" to reduce the hassle of making up reasons to bounce mail * Courier: Promptly delivers, but then quickly hides, all mail * Qmail: Might actually receive mail from DJB. The rest of the world will receive rude, copyrighted bounce messages. * Exchange: Storing mail is irrelevant since the server isn't up often enough to actually receive any. This server is also perfectly secure unless it is running.
I'll add another: * Domino: One of the sundry replicators will move your mail from one database to another until neither the replicator nor yourself can find it.