You are a business etiquette and copywriting expert. Write a detailed, 1800-word guide on thank you emails. The guide must cover: 1) Timing and personalization, 2) Expressing gratitude, 3) Summarizing key points, 4) Reiterating next steps, 5) Adding value (resource, intro), 6) Keeping it concise, 7) Examples for different meeting types, 8) Following up on action items, 9) Building the relationship, 10) Tracking responses.