Email Subject Line Formulas That Work

Why Subject Lines Matter#

47% of email recipients decide to open based on the subject line alone. Here are proven formulas.

Formulas#

The Question#

• "Are you making these email mistakes?"
• "What's your email marketing ROI?"
• Works because: triggers curiosity

The Number/List#

• "7 ways to improve deliverability"
• "3 mistakes killing your open rates"
• Works because: specific, scannable promise

The How-To#

• "How to set up DKIM in 5 minutes"
• "How we increased opens by 40%"
• Works because: promises practical value

The Urgency#

• "Last day: 50% off annual plans"
• "Your trial expires tomorrow"
• Works because: fear of missing out (FOMO)

The Personal#

• "{FIRST_NAME}, your weekly digest is ready"
• "A message from our founder"
• Works because: feels one-to-one

The Curiosity Gap#

• "We almost didn't send this..."
• "The one thing most marketers get wrong"
• Works because: creates information gap

Length Guidelines#

Rule of thumb: Keep it under 50 characters for best results.

What to Avoid#

• ALL CAPS (looks like shouting)
• Excessive punctuation!!! or emojis 🎉🎊🔥
• Deceptive subject lines (CAN-SPAM violation)
• "Re:" or "Fwd:" tricks (destroys trust)
• Spam trigger words: "free", "guaranteed", "act now"