Source : WordNet®

mailbox
     n 1: a private box for delivery of mail [syn: {letter box}]
     2: public box for deposit of mail [syn: {postbox}, {letter box}]

Source : Free On-Line Dictionary of Computing

mailbox
     
        1.  A file belonging to a particular user on a
        particular computer in which received {electronic mail}
        messages are stored ready for the user to read them.  A
        mailbox may be just an {electronic mail address} to which
        messages are sent and may not actually correspond to a file if
        the messages are processed automatically, e.g. a {mail server}
        or {mailing list}.
     
        2.  A destination for interprocess messages in a
        {message passing} system.  A mailbox is a {message} queue,
        usually stored in the memory of the processor on which the
        receiving process is running.  {Primitives} are provided for
        sending a message to a named mailbox and for reading messages
        from a mailbox.
     
        (1994-10-20)