Top row, look for 'User CP' click.
Look down left side.
Use 'Edit Options' to find your default thread subsriptions....select something other than instant email notification. That should stop the emails.
Optionally, to clear all currently subscribed threads..., back on the left side, go to view subcribed threads. Click on Empty Current folder. That should clear all your subcriptions.
If you don't want to subscribe to threads that you reply on, make sure the option box for the subscription is unselected before you his submit when you post.