At the bottom of each thread there is a link that says:  
[img]http://cdn.boardhost.com/mail_light.png[/img] Notify me when someone replies to this topic

If you are already subscribed there is a link in the same place to unsubscribe.  

You would start with the thread's you have started and unsubscribe.  That should eliminate the notification emails.  Except for the private messages.. those would still come.