bbPress Notify (No-Spam)
bbPress Notify (No-Spam), aka bbpnns is a powerful notification plugin designed to send out alerts to all users belonging to selected roles. By default, however, it does not come with support for filtering out people who do not have access to see a given forum.
Requirement: LearnDash + LearnDash bbPress Add-on
LearnDash is one of the most popular LMS plugins for WordPress. Using their add-on for bbPress, you can make it so that course participants have access to one or more forums specific to that course. This bridge add-on will make it so you can set notification roles but only those users who are allowed to view the forums get notified.
There are absolutely NO settings required for this to work. Simply activate it and it will make bbPress Notify (No-Spam) play nicely with LearnDash.