This one works similar to the topic notification already included in phpBB 2. In viewtopic.php, a link appears where the user can subscribe the forum notification with a single click. A second click is for unsubscribing.

The whole thing can be turned on or off for any forum. For example, you won't want users to subscribe a testing forum since this would only cause useless traffic.

The poster's username and the post text are included in every e-mail, so you don't need to visit the forums after every notification e-mail.

English and German languages are included.