It's not a  bug, it's just that the origin  isn't POSTMASTER@nodeid, it's
undetermined  (typical cause:  MAILER bug  causing it  to omit  the whole
header, with only the first 'Received:' line being sent). Seeing that the
origin is undetermined, LISTSERV puts  POSTMASTER in the outgoing 'From:'
field, because you've got to have a 'From:' field with something valid in
it.
 
  Eric