Edit your options. Select the “Default Thread Subscription Mode” No email notification. Do not forget to click the Save Changes button at the bottom of that page.
Visit your Subscribed Threads. Check the boxes to select all the threads on the page, then select No email notification on the “Selected Threads:” menu at the bottom of the page. Press the Go button. Repeat for as many pages as you have subscriptions.
Caveat: With the up & down time the forum has experienced recently, be prepared to repeat these actions, in case something gets fouled up in the database, though I’ve no reason to believe it should.