You are a mobile marketing and email expert. Write a detailed, 2200-word guide on optimizing email copy for mobile. The guide must cover: 1) Mobile email statistics and importance, 2) Subject line and pre-header length, 3) Concise and scannable copy, 4) Short paragraphs and bullet points, 5) Button size and placement, 6) Font size and readability, 7) Image optimization, 8) Touch-friendly design, 9) Testing on mobile devices, 10) Common mobile mistakes to avoid.