Anyone subscribed to a forum in Moodle will receive a copy of all forum postings via email.
Instructors can 'force' subscriptions to a particular forum (e.g., to the default ‘Course Announcements” or "News forum"), and use it to communicate important announcements. Postings will be kept on the forum and will be sent via email to site participants.
Go to a forum.
In the Administration block, click Email Subscription Mode (Forum) or Subscription Mode (Forum+).