Yes! Every time you signup with an email you should have to verify. There's someone who consistently uses my email to sign up for all sorts of things (nearly every piece of mail has his name attached to it). It's actually quiet sad, he seems to be going through hard times right now, and started signing up for what are obviously get rich quick scams.

Same here. Also please make sure that your unsubscribe link works.

When I used gmail I used to have this problem regularly. I just marked every single email I didn't intend to receive as spam which hopefully lowered their rank.