Michael is right.  Any rejection notice due to a user no longer existing,
or because they filled up their mail file (on silly systems that do that
sort of crazy thing) shoudl go back to whoever can delete them.
 
Rejection notices should NEVER go back to the message originator.
 
Rejection notices should NEVER go back to the list itself.
 
Since RFC822 defines SENDER: to be where rejections are supposed to go,
despite the fact that many mail implementations don't follow it, then it
SHOULD define the userid as the prime owner of the list, or at least the
postmaster.  Distributed lists should retain the SENDER: from the original
LISTSERV that keeps the list.
 
It turns out there is another RFC, the number escapes me at the moment,
it might be 850, that defines another header field we have not used yet.
It will solve the problem of USER MAIL AGENTS saving messages in the
correct notebooks.  That field is called  NEWSGROUP:  (or is it NEWSGROUPS)
I will look for it and post here.  It should identify the list as a full
address, userid and node.