Turgut is right.  Here is my boilerplate for returning
to the sender of such a message:
 
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.