I recently signed up for a firefox sync account, and since then have been receiving newsletters. I visited the unsubscribe link many times in the emails and fully unsubscribed, yet I still receive the news letters. I went a step further and fully deleted my account because the news letters wouldn't stop. After deleting the account I sign in to my email today and still see I'm receiving emails even though the unsubscribe process says it was successful.

Is the unsubscribe process broken?