Well, sending the question to DEAR-BOD  might be appropriate. This way it
would be on the  agenda of the next BoD meeting, and  they might come out
with  a Directive  for  the Prohibition  of  Non-Standard Mail  Gateways,
"Standard" being  defined as per  a Future  Proposal from a  Gateway Task
Force.
 
Since  this question  affects the  whole network  and is  of interest  to
everybody, I will answer it. The  best recommendation is to use a subject
starting with UNDELIVER (case is irrelevant). There are a number of other
'tabu' subjects,  like RETURNED NETWORK MAIL.  In any case, a  copy of at
least the original header,  IN RFC822 FORMAT (ie NOT in  JANET or UUCP or
X.400 form), should be included in the BODY of the rejection notice.
 
  Eric