Restrict users from sending mail to groups

Does anyone know another way to restrict users from sending mail to groups/large number of users? This document was found in the KB but is there another way to do this i Domino 7?

http://www-12.lotus.com/ldd/doc/domino_notes/Rnext/help6_admin.nsf/855dc7fcfd5fec9a85256b870069c0ab/2973585b7849042285256c1d003958d8?OpenDocument

Subject: Restrict users from sending mail to groups

Have you looked at server based mail rules?I think you prevent users sending to more than a specified amount of recipients. Not sure if you can mention groups in there or not.