The document 'RFC733 STANDARD' is available on NICSERVE.  Basically,
it is very similar to RFC822, but it permits the word 'at' instead of '@'
in mailbox names.  Admittedly, providing for RFC733 is a throwback, but I
personally have received RFC733 mail more than once in the past year from
non-IBM NOTE senders.  Naturally, the viewpoint of a Mail User Agent
maintainer is different from that of a LISTSERV maintainer (if my program
can't reply to a message, then I am directly inconvenienced), so I can't
really argue that LISTSERV should make *any* concessions to NOTE -- the
pedagogical value of disenfranchizing all NOTE users would be immense,
provided, of course, that you could stand the heat from said NOTE users.
                                       John