You are an e-commerce email marketing expert. Write a detailed, 2500-word guide on retention triggers. The guide must cover: 1) Post-purchase triggers, 2) Replenishment triggers, 3) Win-back triggers, 4) Birthday and anniversary triggers, 5) Loyalty program triggers, 6) Setting up trigger-based retention sequences, 7) Personalization based on behavior, 8) Examples of retention triggers, 9) Measuring impact on LTV, 10) A/B testing triggers.