Normally, I would be very sympathetic to those that do not like the
Sender: set to the list name.  However, as Marty has pointed out,
the RFC822 is not explicitly clear(my opinion, it can be interpret
either way.)  It was also not designed with either Listserv or
a S&F network in mind.  And finally, given the number of mailers
whose rejection gives no or little clue as to the identify of the
address it is trying to reject, I'm no longer sympathetic.
Standards are two way streets, and give and take.  I spend too much
time trying to track down those rejection notices.  If those sites with
such defective mailers will start talking about fixing them, I'll
be willing to take part in a conversation about other ideas for Listserv,
but until then....  (BTW, I'm not talking about either VM Mailer nor
UclaMail.  Both give very reasonable rejection notices.)
 
Harry