I (user1) set up a dummy EPDM user (BOMuser) to receive notifications.  Dummy user's (BOMuser) email is an Exchange email distribution group.  If I (user1) initiate a Change in State with BOMuser as a notified user, user1's email gets multiple copies of the same notification (11 times last time I did it).  It does not seem like any other recipients of the notifications gets multiple copies.  Why and what can I do about it?

This itself is a workaround to the problem of some users are blocking notification emails using the Tools|Notify|My Notifications dialog.  I was trying to force the users to receive certain notifications.  Is there a way for sysadmin to prevent them from blocking notifications?