You are an email marketing analytics expert. Write a detailed, 2300-word guide on using CLV in email. The guide must cover: 1) What is CLV and why it matters, 2) Calculating CLV with predictive models, 3) Segmenting customers by CLV, 4) Personalizing emails for high-value customers, 5) Retention strategies for high CLV, 6) Win-back for high-value churned customers, 7) Lookalike modeling for acquisition, 8) Tools for CLV prediction, 9) Examples of CLV-based email campaigns, 10) Measuring impact on retention and revenue.