In the bustling world of email newsletters, open rates seem like a straightforward metric: just a percentage of people who bother to click open. But there is a ton of value hidden beneath the surface, much like spotting a raw diamond in the rough. You might correctly identify it as a stone, but it takes polishing and faceting to reveal its true luster. Viewing open rates as merely "did they open or not" is like seeing just the rough stone; once you clean the signal, segment