[If you're talking about receiving emails when new replies are posted...]
You have to do the following on each thread you want a notification email on:
* either reply to it (which would automatically subscribe you)
* or go to Thread Tools and choose "Subscribe to this thread"
Make sure that "Default Thread Subscription Mode" in Edit Options of User CP is set to "Instant Email Notification".
If you are referring to linkbacks that is a back end software thing and there won't be any way for you to control them.
__________________
Sing to a sailor's courage, Sing while the elbows bend,
A ruby port your harbor, Raise three sheets to the wind.
......................-=Krynnish drinking song=-