mci mail

from The Free On-line Dictionary of Computing (8 July 2008)

MCI Mail

   <messaging> The first commercial Internet {electronic mail}
   service, launched by {MCI} in about 1981.  {Vint Cerf} was the
   chief engineer.

   Reading mail was free but you had to pay to send.  Users
   discovered you could communicate for free by sharing an
   account.  One user would save a message as a draft and the
   other would read it and replace it with his response.

   (2004-08-25)