Source : Free On-Line Dictionary of Computing

mail server
     
        1.  A program that distributes files or
        information in response to requests sent via {electronic
        mail}.  Examples on the {Internet} include {Almanac} and
        {netlib}.  Mail servers are also used on {Bitnet}.
     
        In the days before {Internet} access was widespread and {UUCP}
        mail links were common, mail servers could be used to provide
        remote services which might now be provided via {FTP} or
        {WWW}.
     
        2.  (Or "mail hub") A computer used to store and/or
        forward {electronic mail}.
     
        (1995-05-05)