>  As far as I can tell, this is an email problem, not a LISTSERV(R)
>  problem.  LISTSERV(R) might be able to ameliorate, but it can not 100%
>  prevent sender and receiver from screwing up each other.

  I disagree.  If Listserv stuck to (or at least had the option to)
distribute nonexecutable text-only messages virus contamination would not be
a problem.  As it is, Listserv distributes all files attached with the text
message, virus and all.  The newest viruses/worms do not even require that
the file be opened in order to infect the recipient PC -- it only requires
the right "host" be present, usually a Microsoft program like Outlook or
Word.  Listserv definitely needs the option to distribute text-only messages
without any attached files.  Apparently that used to be an option when you
set a files=no option in the header.
   I use McAfee AntiVirus.  A new virus database is available about every 10
days and maybe every month a new engine update is available.  That engine
update frequency alone tells you how fast viruses are evolving.  I would
expect frequent database updates, but frequent engine updates to detect the
new viruses is alarming.  This isn't your father's internet anymore, to
borrow a phrase from Olds.