Email Subject Line Optimizer
PROGenerate and A/B test email subject lines to maximize open rates. Apply psychological triggers, personalization, and spam-safe patterns for 45%+ opens.
Example Usage
Generate 5 A/B test subject lines for an e-commerce flash sale ending tonight. Target active customers who purchased in the last 60 days. Brand voice is friendly and urgent but not aggressive. Personalize with customer’s first name. Keep under 50 characters. Avoid spam triggers like ‘FREE’ and ‘ACT NOW.’ Focus on scarcity and exclusivity. Include one question-based variation and one benefit statement variation.
Skill Prompt
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How to Use This Skill
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Suggested Customization
| Description | Default | Your Value |
|---|---|---|
| Target character count for subject lines (30-50 recommended for mobile) | 40 | |
| Brand voice: formal, casual, funny, urgent, educational, knowledgeable_helpful | professional_warm | |
| Depth of personalization: none, first_name, company, purchase_history, feature_viewed | first_name | |
| Primary tactic: curiosity, urgency_scarcity, social_proof, benefit_driven, question_based, mixed | benefit_driven | |
| Audience segment: new_subscribers, active_customers, at_risk, churned, high_value, b2b_enterprise, ecommerce | general | |
| Risk level: ultra_low, low, medium, high. Balances deliverability vs. persuasiveness | low |
Research Sources
This skill was built using research from these authoritative sources:
- AI email subject lines that drive 3x more revenue Official HubSpot guide on AI-powered subject line generation, testing, and personalization with brand voice parameters
- How AI Can Improve Your Email Subject Lines Mailchimp's resource on AI-driven subject line optimization, A/B testing automation, and result interpretation
- Best Practices for Email Subject Lines Official Mailchimp documentation on customizing, testing, and factors affecting subject line performance
- A/B Testing Email Subject Lines In-depth guide on A/B testing methodology, sample size requirements (1,000+ minimum), and achieving 45%+ open rates
- How to Write Email Subject Lines That Get Clicked in 2025 13 practical tips including mobile optimization, benefit-driven messaging, and strategic word choice
- 150+ Email Subject Line Examples and Expert Tips Expert tips with examples covering best practices, psychology-backed strategies, and testing frameworks
- Subject Line Hacks and Strategies Community strategies from Reddit's lead generation community on brevity, personalization, and curiosity tactics
- Subject Line Consumer Psychology Tips LinkedIn deep-dive into psychological principles: curiosity, scarcity communication, and humanization
- Email Marketing Case Studies Real-world case studies showing successful A/B testing protocols, segmentation strategies, and metrics
- Psychology of Email Subject Lines Seven psychological strategies for maximum engagement using cultural references and prospect motivations