When you get an email you have a number of choices.

A BIG FAIL is when someone like your teacher sends an email to the whole class and instead of replying to them you click REPLY ALL. Please don't do this.

It is better to simply reply to the person who sent the email. There are not many times that everyone who got the email needs to see your reply.

Check out the recording below to see what to do and then have a go.