If you're referring to how you sometimes get an e-mail when someone posts to a topic, click the "UNNOTIFY" link at the top or bottom of the thread. While I never click "NOTIFY," I've found that if I post to a thread via the Tapatalk app (usually because I want to post a picture), the app automatically subscribes me to notifications for that thread and then I get e-mails, although they usually land in spam. Clicking "UNNOTIFY" solves the problem if I forget to unsubscribe myself via the app.