Go to your 'usercp', and options. Turn of the option to be emailed when someone posts in a thread you have. Then click unsubscribe on all of the threads you are subsribed too.
"Use 'Email Notification' by default?
Using this option emails you whenever someone replies to a thread that you have participated in."
to No. If you don't, you will receive an email each time someone posts to a thread you have also posted to.
6. If you are registered and didn't do (5) above, then do it now in your control panel. Also, in your control panel, turn off subscription for each thread showing you as subscribed.