User Jasper's instructive comment under How to phrase a follow-up question politely, if there's evasion? motivated this question:
Dale Carnegie's How to Win Friends and Influence People addresses many similar topics. (Unfortunately, I don't think it addresses this exact topic.) The best editions of the book were published before he died in 1955.
I was wondering if there other reputable books or references on the subject of writing politely or cordially, but with conviction and effect.
What's this subject or practice or method called, so that I can try searching?