Beginner

AI-Powered Subject Lines

Your subject line determines whether your email gets opened or ignored. AI can generate dozens of high-performing subject line variants in seconds, giving you more options to test and optimize for maximum open rates.

Subject Line Formulas for AI

FormulaExampleBest For
Curiosity GapThe email strategy that 10x'd our revenueNewsletters, announcements
How-ToHow to write emails that actually get repliesEducational content, tips
Number + Benefit5 subject line tricks for 40% higher opensListicles, roundups
QuestionAre your emails landing in spam?Problem awareness, engagement
UrgencyLast chance: 50% off ends tonightPromotions, deadlines
Personal{First_name}, I noticed something about your accountBehavioral triggers, sales
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Pro Tip: Ask AI to generate 20 subject lines for each email, then pick the top 3-4 for A/B testing. Include the email context, audience, and desired emotion in your prompt for better results.

Preview Text Optimization

Preview text (preheader) is the second line readers see. AI should generate subject line and preview text as a pair:

  • Complement, do not repeat: Preview text should add information, not echo the subject line
  • Extend the hook: Continue the curiosity or value promise started in the subject line
  • Include a CTA hint: Give readers a reason to open by previewing what is inside
  • Keep it concise: 40-90 characters is the sweet spot for most email clients

Subject Line Length and Formatting

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Mobile Optimization

Keep subject lines under 40 characters for mobile display. AI can generate both short and long variants for testing.

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Emoji Usage

AI can suggest contextual emojis that boost open rates. Test emoji vs. no-emoji variants to find what works for your audience.

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Capitalization

Test title case vs. sentence case vs. lowercase. AI generates all variants so you can discover what resonates with your list.

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Spam Avoidance

AI checks for spam trigger words and suggests alternatives that convey urgency without triggering spam filters.

Personalization in Subject Lines

Beyond first names, AI helps you personalize subject lines with:

  1. Behavioral data: Reference recent actions (browsing, purchases, downloads)
  2. Segment-specific language: Different value propositions for different audience segments
  3. Location-based: Incorporate city or region for local relevance
  4. Lifecycle stage: Different messaging for new subscribers vs. loyal customers