See section 5.2, 2nd to last item:

http://www.lsoft.com/manuals/1.8d/qs/qs.html#RejectedPost
but more to the point:
http://www.lsoft.com/manuals/1.8e/owner/owner.html#_Toc9154234

At 16:51 10/24/2002 Thursday, Dave Botwin................Tower wrote:
 >
 >"The enclosed message, found in the SIGMABETA mailbox and shown under
 >the spool ID 0088 in  the system log, has  been identified as a
 >possible delivery error notice  for the  following  reason: "Sender:",
 >"From:"  or "Reply-To:"  field pointing to the list has been found in
 >mail body."