May I  kindly remind  everyone that  "Filter=" was not  designed to  be a
mechanism to filter  naughty people from a mailing  list, although people
do use  it for  this and  it does  work in  that capacity.  "Filter=" was
originally  introduced as  a  loop prevention  mechanism,  to extend  the
built-in list of  broken gateway addresses, which  hopefully you wouldn't
consider sensitive information.
 
The  reason "Filter="  was  put in  the  list header  is  that there  are
currently two mechanisms under list owner control to customize a list:
 
1. The list header.
 
2. The MAILTPL file.
 
Hopefully you will agree that the template for administrative messages is
not a  good place to tell  LISTSERV which gateways (or  naughty users) to
ignore mail from, or to  store other operational directives. Besides, the
MAILTPL file can be retrieved by list members (although you can configure
it otherwise). It isn't meant to contain sensitive information.
 
So  your  question really  is:  "Why  wasn't  a brand  new  customization
mechanism developed specifically for the Filter= facility?" Well, off the
top of my hat:
 
- It would take a serious amount of work.
 
- It would add yet another file for each list, just for "Filter=".
 
- It would have to be documented carefully with many examples.
 
- People would have to get used to it.
 
- It would make LISTSERV more complicated, just for "Filter=".
 
  Eric