I've never used email-notification ever, but that is my assumption. I don't think you'll be automatically emailed each time someone posts in every thread you have participated in - that is just silly!
I think you should subscribe to the thread(s) in question, to be able to receive email notifications. I made a suggestion a while back concerning filters, much like subscribed threads (and forums), but filtering out forums which you would have no interest in (for example Languages, History, etc) - that way, whenever you check new threads, you will only see sections such as:
IT Stuff
Non-School
School
UAI/HSC Guidance and Counsel, for example.
Try subscribing to each thread, and see if you get any emails. (obvious question: have you enabled email notifications?).