a public box in which mail is placed for pickup and delivery by the post office.
a private box, as at a home, into which mail is delivered by the mail carrier.
Computers. a file for storing electronic mail.
(mainly US & Canadian) a slot, usually covered with a hinged flap, through which letters, etc are delivered to a building a private box into which letters, etc, are delivered Also called (in Britain and certain other countries) letter box
(mainly US & Canadian) a public box into which letters, etc, are put for collection and delivery Also called (in Britain and certain other countries) postbox