Thank you for contacting the Canvas Community. We're sorry to hear you've been experiencing issues with messaging a student in canvas. Thanks for explaining your question thoroughly but unfortunately, no you need to be in the same course at some level (any level) to message a student using the canvas messenger. It does not function like your normal school email server. The conversations feature is intended to facilitate communication between users that share a course together. You can either enroll yourself as any role within the course to message them, or you'd need to use your school provided email and send the student a message directly that way. Hopefully this helps!