Comprehensive Guide to Seasonal Email Marketing

Write a comprehensive 1500-word guide on creating effective seasonal email marketing campaigns for [INDUSTRY TYPE] businesses. Include sections on: 1) Planning timeline for major holidays/seasons, 2) Subject line strategies with 10 examples, 3) Email design best practices specific to seasonal content, 4) Segmentation strategies for different customer types, 5) Promotional strategies that don't rely solely on discounts, 6) A/B testing ideas specifically for seasonal campaigns, and 7) Post-campaign analysis metrics. Include real-world examples and data points where possible. The tone should be informative yet conversational, appealing to marketing managers with intermediate experience.