i did a quick search on 'notifications' and found the following threads, which should help you to turn them off. if you don't have any success, please let me know & i'll see if i can help further...
http://www.detroitgothic.net/index.php?/topic/35415-pms-profile-comments/#comment-729346
http://www.detroitgothic.net/index.php?/topic/15260-getting-way-too-many-emails-from-dgn-all-the-sudden/#comment-313489