If you go to your
"User CP" (<---linky) and look down the lefthand side, you will see an option for
"List Subscriptions" (<---linky). From here you can control the notifications for the threads you have subscribed to.
Note that posting in a thread by default subscribes you to it. If you want to change the default behaviour, in the panel down the lefthand side is a label,
"Edit Options" (<---linky). Under the "
Messaging & Notification" box you will see "
Default Thread Subscription Mode". It is there you can change the default subscription behaviour.
Yours optionally,
Adrian