I accidentally sent an email in Canvas to my entire class that was only meant for one student -- it was personal about one of their assignments that is incomplete. Is there any way to redact this email so the entire class can't see it anymore?
vartouhi.asherian, the answer to this is almost undoubtedly "no." You could contact Canvas Support to see if they can work some magic, but even if they can remove the message itself from Canvas, any students who have their notification preferences set to receive external notifications of messages "Right Away" will already have received emails of the message. This is a bell that cannot be unrung. I'm sorry to hear that this happened.
vartouhi.asherian, unfortunately we've had this happen before and stefaniesanders is completely correct about it being almost impossible to contain. I would second her recommendation of contacting Canvas Support (or your Canvas Admin's) ASAP and seeing if they can remove the message from Canvas. Yet, something else you could do is contact the people in charge of student email at your school and see if they can go in and wipe the message from the student email as well. This is something we did and it seemed to help. Yet, ultimately if students get Canvas Inbox messages sent to other email addresses or texted to them then the cat is out of the bag and can't be put back. 😞