The Free On-line Dictionary of Computing (30 December 2018):

Listserv

    An automatic mailing list server, initially
   written to run under IBM's VM operating system by Eric
   Thomas.

   Listserv is a user name on some computers on BITNET/EARN
   which processes electronic mail requests for addition to or
   deletion from mailing lists.  Examples are listserv@ucsd.edu,
   listserver@nysernet.org.

   Some listservs provide other facilities such as retrieving
   files from archives and database search.  Full details of
   available services can usually be obtained by sending a
   message with the word HELP in the subject and body to the
   listserv address.

   Eric Thomas, has recently formed an international corporation,
   L-Soft, and has ported Listserv to a number of other
   platforms including Unix.  Listserv has simultaneously
   been enhanced to use both the Internet and BITNET.

   Two other major mailing list processors, both of which run
   under Unix, are Majordomo, a freeware system, and
   Listproc, currently owned and developed by BITNET.

   (1995-02-22)