From YOGI:

Go to MyS2K -> Email Settings. There are two new checkboxes at the bottom which control emails on/off for topics or forums. If you check the box for topics, you'll get email for all of your topic subscriptions. Same thing for forums, you'll get email for all of your forum subscriptions. Nothing else controls email notification, just these two boxes. Note that you have to actually be subscribed to a topic/forum to get email notifications, ie it must show up in your topic/forum subscriptions list in MyS2K.