First, it's worth noting that uninstalling Firefox won't help because it has nothing to do with the Mozilla mailing system. This is a known issue. Some emails don't get unsubscribed once you change the address associated to your Firefox Account and the unsubscribe button at the bottom of the email requires you to login to change the setting. The workaround is to go to [https://www.mozilla.org/newsletter/recovery/ Mozilla's email preference center]. There you enter your email address that you want to manage and you will get a link in your email to the page where you can manage your subscription status to all Mozilla newsletters. Under some circumstances, I have seen users whose management page tells them that they aren't subscribed to Firefox Account emails. If that's the case, usually if you subscribe, save the changes and then unsubscribe it will set it into the correct unsubscribed state. Hope this helps.