You are an email copywriter and customer experience expert. Write a detailed, 1800-word post on thank you emails. The post must cover: 1) Expressing genuine gratitude, 2) Personalizing the message, 3) Including next steps, 4) Offering additional value, 5) Encouraging social sharing, 6) Making a relevant offer, 7) Using warm and friendly tone, 8) Examples for different scenarios, 9) Timing and delivery, 10) Measuring engagement.