How do I write official mails?

This is a question that I hear often while training. I guess the question should be, 'How do I write professional emails'?
Here are a few points that will help in giving a professional finish to your emails:

1. Be clear about why you are writing the mail - what is your objective?
2. Is there any secondary information that will complement what you are conveying?
3. What are the action points you want from the mail, or what is the response you want?
4. Is the structure and logical flow sounding good?
5. Have I left enough white space in my mail?
6. Have I kept the audience in mind while writing?
7. Is my subject line, salutation and signature sounding casual or professional?
8. Are there any grammar errors?
9. Have I done a check after writing?

Well, I hope to have got the 80% of it. Try this and let me know.