Setup Install mailcatcher and configure it as your smtp server ( https://blog.danpoltawski.co.uk/2014/10/testing-email-features-with-mailcatcher/ ) Clear allowedemaildomains setting and emailfromvia settings Add two users, one with @example.com email address Enrol one @example.com user as teacher in a course, other user as student You'll need to repeat this a number of times for the cases below: As teacher post a forum post in announcement forum, tick the 'no editing time' button Run php admin/tool/task/cli/schedule_task.php --execute=\\mod_forum\\task\\cron_task to enforce the mail being sent out View the headers of the mail's source tab in mailcatcher and pay attention to the 'From' field. Case 1 When you first conduct this test with default settings, the mail should always be formatted so From is " Name (via siteshortname) <noreplyaddress> " Case 2 Now add " example.com " to the allowed domains, it should then become: " Name (via siteshortname) <realaddress@example.com> ". Case 3 If you set emailfromvia to " Only when from a no-reply address " it should become " Name <realaddress@example.com> "