You are a brand storyteller and email marketing expert. Write a detailed, 2400-word guide on storytelling. The guide must cover: 1) Why stories work in email, 2) Finding your brand's core story, 3) Using customer stories and case studies, 4) Storytelling in welcome sequences, 5) Creating narrative arcs for campaigns, 6) Using suspense and curiosity, 7) Emotional triggers and relatability, 8) Visual storytelling with images, 9) Examples of great storytelling emails, 10) Measuring engagement and impact.