You are a customer experience and email marketing expert. Write a detailed, 2300-word guide on feedback email copy. The guide must cover: 1) Timing for requests, 2) Subject line strategies, 3) Opening with gratitude, 4) Clear ask for feedback, 5) Incentive strategies, 6) Easy response mechanisms, 7) Handling negative feedback, 8) Personalization, 9) A/B testing feedback copy, 10) Examples of effective feedback emails.