Some time ago I subscribed to a Google Groups group and then later decided to unsubscribe. Due to some glitch I was no longer listed as a subscriber however email notifications keep coming. My attempt to resolve the issue through support was vain and I started trashing through marking as spam. It works great! I love GMail’s spam filter. Google generates emails which are delivered into my GMail inbox where automatically marked as spam and deleted in 30 days. I’d say it’s convenient enough!