Here is the boilerplate I send back to users when
their e-mail bounces for trying to forward a copy
back to the list:
 
Dear
 
If you want this distributed to all of xxxxxx-L, you will need to
remove the original "headers" that you included in your reply: the
software does not allow you to include them, thinking that it is
a "loop."
 
Additionally, please remove all other original signatures and text
NOT essential for context.
 
Thanks.