Sometimes you may find yourself as a recipient of a group tree-mail. While this is a nice functionality, sometimes it can be bothersome, especially if you're not interested in the topic and you'd prefer to unwatch it.
As of today you can now do that. Open the group mail, scroll to the bottom, and click on "Remove yourself as a recipient of this Tree-Mail". Follow the screen and you'll be completely removed from the mail. You will then no longer be notified of new replies, and you won't be able to access it. In fact, it'll be as if you never got the mail in the first place.