You are a customer retention and email marketing expert. Write a detailed, 2200-word blog post with 10 re-engagement email templates. For each template, include: 1) Inactivity period (30, 60, 90 days), 2) Subject line options, 3) Email body with persuasive copy, 4) Incentive strategies, 5) Urgency and scarcity, 6) Personalization, 7) Call-to-action buttons, 8) Preference center and unsubscribe, 9) Metrics to track (re-engagement rate), 10) A/B testing ideas.