There are STILL a  number of mailers out there that  use the RFC822 "To:"
info to decide where to deliver the messages. So here is what happens:
 
1. Joe posts to list.
 
2. LISTSERV forwards to moderator.
 
3. Moderator approves and forwards back to list.
 
4. LISTSERV distributes happily.
 
5. Broken  mailer gets  message, sees  "To:" line,  and delivers  back to
   list.
 
6. LISTSERV forwards to moderator.
 
It can  be difficult to identify  the failing addresses, but  at any rate
the message should not be distributed a second time.
 
  Eric