Here is an example of email you should never send.  This is an actual email, the name has been deleted.

From: xxx

To: Klinger, William

Subject:

Hey Mr. Klinger sorry i had to leave class early the other day but i just wanted to know if i'm fialing this class or not or close like i been doin all my homework and im goin to extra credit this week so will that help?...

This is even worse.

yea let me kno when your free and ill meet u there