I do use Blackboard for one operation – notifying students in bulk. It does perform that function fairly well. However, in typical fashion, the interface to get that done is just short of intuitive.
Before submitting the announcement, or notification, or whatever it’s called, there are several choices. One of which asks you to decide if you want to “send a copy of this announcement immediately.” You can indicate in the affirmative by checking the box. However, if you don’t check the box, the italicized text seems to say that they will still be notified. Maybe just not immediately. So then when? Later today? Tomorrow? Next week? Clarity is not their strong suit.