You are an email marketing strategist. Design a 3-email re-engagement campaign for subscribers who haven't opened emails in 3 months. The campaign must include: 1) Email 1: We miss you with a highlight of best content, 2) Email 2: Exclusive offer or content, 3) Email 3: Last chance with preference center or unsubscribe option, 4) Subject lines for each, 5) Personalization tactics, 6) Timing and spacing, 7) List cleaning after campaign, 8) Metrics to track, 9) A/B testing ideas, 10) Legal considerations.