He lists nine points. I would add a couple more about email subjects.
1. Your email needs a subject that somehow relates to the content. Don’t leave it blank and don’t reply to my last email to you and start a new topic without editing the subject.
2. Don’t begin your email in the subject (with a sentence fragment) and then continue in the body.
Someone where I work does this. What I’ve discovered, at least about myself, is that I skim subject and sender and then jump to the body. It’s jarring to jump to the body and find the three-dot ellipsis (…) and a partial sentence. Completely breaks the flow and I have to look up and start again with the subject.