Email etiquette

Today I learned that with email etiquette use must always use the correct spelling, punctuation and manners. 

You must never use slang and  inappropriate content when you are emailing your teacher  unless if you want to get a demerit.
You must always proofread your message so your teacher knows who this message is from.
You must make the message short and sweet you mustn't go and make it an hour long.
Don't include teacher's full name cause it's rude and it's bad manners.