click settings(top right of main forum page),on the next page click general option on the left, then 3rd option down is -Default Thread Subscription Mode:, change to- through my control panel only. you will still be able to see your subscribed threads but wont get emails every time someone replies to them.
Alternately u goto profile/subscribed threads and tick the boxes on your subscribed threads then change the options for each one by clicking selected threads at the bottom of the page, and choosing the option u want.. (useful if u only want emails for some of you thread subscriptions).
hope this helps.