Problem: Some users have reported that when subscribed to a discussion board forum, they are not receiving emails as expected when someone posts a message in that forum.
Solution: Blackboard has confirmed this as a bug, in which some users in a course have their subscriptions erroneously disabled when another user is removed (i.e. drops and/or withdraws) from a course. This is fixed in the next version of Bb, however there are no workarounds available.