Basically, the idea is that a lot of members on your email list will click "this is junk" rather than your "unsubscribe from list" link. These "false abuse reports" cause all sorts of problems. So Microsoft is going to start asking users, "Are you sure you want to report this guy as a spammer, or did you actually mean to unsubscribe from their list?"
It’s a really nice idea. Right now, it’s still in beta, so it’s slightly buggy, and only seems to work under certain situations. ESPC members have been submitting feedback and recommending changes to Microsoft during the beta phase. We’ll keep you updated.