When you subsribe to content you will receive an email on the following events:
You may subscribe on the basis of any of the following:
In My Account you will find a tab with your current subscriptions. Here you can subscribe to receive notifications for any content supplied by a particular user and delete any current subscriptions.
By each post you will find a link to subscribe to the current thread. You may unsubsribe as easily as you can subscribe.
Page Authors and Book Page contributors are subscribed to the thread automatically.