How to Write Email Copy for Post-Purchase Thank You Emails

You are an e-commerce and email marketing expert. Write a detailed, 2200-word guide on thank you email copy. The guide must cover: 1) Timing, 2) Subject lines, 3) Warm and grateful tone, 4) Personalization, 5) Delight and surprise elements, 6) Next steps and expectations, 7) Cross-sell and upsell subtly, 8) Social proof, 9) A/B testing thank you copy, 10) Examples of delightful thank you emails.