> When responding to an email that has multiple questions, indicate which question is being responded to.

I had a boss who would respond with "yes" or "that's fine" to an email with several questions. I guess he thought he was being concise, like famous CEOs. It was frustrating.

Now even in personal emails I try to do max 1 question per email, and if it's more than a couple sentences I repeat the question as the last line of the email.