Currently, if a teacher wants to communicate with all his students in a course, he must create a campaign in the marketing section.
First, to our opinion, teachers shouldn't have access to the marketing section as they are not concerned by marketing.
Moreover, it's quite heavy to create a campaign just to send a simple message. It would be nice if, in the course list, the teacher can directly click a button (or through the 3 dots menu) to send an email to all the enrolled students, for instance to inform about a modification in the schedule, or alert about something not to forget.