Try this link--hopefully it will take you to the page where you can edit your notifications. If it doesn't, go to the top of this page and click on Settings then in the left hand column is Subscriptions. From there you should be able to make changes to all subscribed threads.
Set "Default Thread Subscription Mode" to be "Through my control panel only".
That will stop any new threads from emailing you when you subscribe (by replying I believe). You may still have to go to all the threads you have already subscribed to to shut them off individually, but I would just shut them off as you get an email from them because some will die on their own anyway.