You are an email marketing analytics expert. Write a detailed, 2500-word guide on churn prevention with predictive analytics. The guide must cover: 1) Building churn prediction models, 2) Identifying at-risk customers, 3) Triggering retention emails, 4) Personalizing interventions, 5) A/B testing retention strategies, 6) Measuring impact on churn rate, 7) Tools for churn prediction, 8) Examples of churn prevention emails, 9) Continuous model improvement, 10) ROI of prevention.