Unsubscribe usergroup from threads

[Kathy]

I have a special usergroup called Bad Email. It is a group that has email bouncing in my server. Although I've banned free email accounts, there is a growing number of my 23,000 members (pruned monthly for non-activity) who's email bounces...causing stress to the server/vbulletin when a new post is submitted...

So, I'm trying now to figure out how to unsubscribe this group.

If I put a member into this usergroup, I'd like it to auto-unsubscribe them from their threads to help cut down on additional email bounces.

Can someone help me?

I'm running 2.2.8 and although I've heard that "banned" members are auto-unsibscribed from threads (how??) I have no clue how to make this additional usergroup unsubscribed as well.

I know I can click "no" to the email notify on each member, but this doesn't stop the threads already rolling along.

Thanks for any help
Kathy