You are an email marketing and copywriting expert. Write a detailed, 2500-word guide on holiday email copywriting. The guide must cover: 1) Subject lines for different holidays, 2) Opening with festive relevance, 3) Aligning offers with holiday themes, 4) Visual and design elements, 5) Urgency and scarcity, 6) Calls to action, 7) Personalization for holidays, 8) A/B testing holiday copy, 9) Examples of effective holiday emails, 10) Planning a holiday email calendar.