how do you send message or email to everyone in the course ?

If you can't figure it out, the prof has probably turned off that function. Because it is pretty annoying to get all kind of beatifications for mass emails to six hundred students.

In Avenue, go to the course, click on the communication tab, classlist, select who you want to email to then click email and compose your message

You take a sticker, write annoying on it, then smack it onto your face.

It is very frustrating to get tons of emails from everybody asking for little things. It is not hard to ask someone in your tutorial/lab, ask a friend, ask a neighbour in class, or email the professor or TA if you missed the lecture. I would never send a mass email to 600+ people unless it was urgent. That's my two two cents.

I've never ever gotten a "mass email" that actually needed to be sent to the entire class. It's the most annoying thing ever. If there is ANY way to deal with your problem that doesn't involve spamming your class, that's what you should be trying to figure out before you even consider how to send mass emails.

good. people are already bashing mass messages.
what i would like to know is how you turn that off, so i would stop getting emails requesting for notes or lecture recordings.