This is just an educated guess (based upon some probing and other facts
this a.m.):  WEBTV.COM users get their MITVMA.MIT.EDU LISTSERV
distributions via the LISTSERV backbone at PLUM.EASE.LSOFT.COM.  A delay
in one of the lists that I subscribe to in DIGEST mode and that uses that
related backbone site, says to me that PLUM (LISTSERV, SMTP, ???) was not
distributing until  Fri, 5 Mar 1999 8:29:20 -0500

WEBTV users could have mailto:[log in to unmask] to
verify this guess.

/Pete Weiss at Penn State