1. Use a greeting, say hello, by maybe saying Dear Sally or Hello Sue.
2. Use a professional font, never decorative.
3. Don't write an email how you text. It could be confusing to the person reading it also if it was a email to your boss you would not want to send it like that.
4. Keep it short if you have a lot to say, just say it to their face.
5. Be to the point.