You need to remove yourself from each forum individually:
Click on this link,
http://moodle.org/mod/forum/index.php?id=5
and then look under the column that says SUBSCRIBED.
If it says YES, click on the YES and it will change it to NO, and you will no longer receive emails from that particular forum.
Do this for each forum that says YES, that you no longer want to be subscribed too.