Most unanswered emails share one failure: they ask the reader to work. The fix is to write the email the way you would hand someone a note — a subject that says what it is about, three sentences that say what you want, and a single question with a deadline. "Could you confirm by Friday?" beats "Let me know your thoughts" every time.
The subject line is the headline: "Invoice attached for review" is a task; "Quick question about the invoice" is a favor. Write the subject after the body, so it says what the email actually contains. If you cannot summarize the email in eight words, the email is not ready.
The final rule is about replies, not drafts: answer the question first, then add context. The person who reads "Yes — see the note below" before anything else will open your next email without hesitation. Brevity is not rudeness; it is respect for the reader's calendar.