How to Write Email Subject Lines That Get Opened

Imagine this.

It’s Monday morning. You’re groggy, clutching your first cup of coffee, and scrolling through an inbox stacked with overnight emails.

Twenty subject lines compete for your attention.

• “Newsletter #48.” Meh.
  
• “Important Update.” Important for who?
  
• “Big Sale Ends Tonight.” Maybe later.
  

Then one catches your eye:
“The 3 mistakes killing your traffic (and how to fix them).”

Boom. Click.

That’s how subject lines work. They’re tiny billboards in a crowded inbox highway. And if yours doesn’t spark curiosity or signal value in under three seconds, you’re invisible.

Your email could hold gold—free guides, life-changing insights, and even the deal of the year. But if the subject line flops, no one ever sees it.

That’s why mastering subject lines is the highest ROI writing skill in email marketing.

Think back to the inbox moment. Why did you open one and ignore the rest?

It usually comes down to five things:

• Clear → No puzzles. If I don’t “get it” instantly, I scroll past.
  
• Short → Under 50 characters. Anything longer gets chopped on mobile.
  
• Relevant → If it feels written “for me,” I’ll click.
  
• Emotional → Curiosity, urgency, excitement—emotions move the thumb.
  
• Actionable → It promises a payoff: learn, save, get, fix.
  

Story check: A SaaS founder once told me, “We changed one subject line from ‘Monthly Report’ to ‘Your traffic doubled this month (see inside).’ Our open rate jumped 38% overnight.”

Mini takeaway: Subject lines that hit at least two of these five usually outperform the rest.

Here’s a mistake beginners make: they write for themselves, not their reader.

Picture two subscribers:

• Sarah, a CMO racing between meetings.
• Jake, a new freelancer hunting for tools.
  
  

Same inbox. Different worlds.

Sarah doesn’t want “fun hacks.” She wants ROI. Something like: “Cut your reporting time in half.”
Jake? He’s hungry for tips and belonging. He clicks on: “The freelancer’s guide to landing first clients.”

Timing plays into it too:

• Morning → positive, quick wins.
  
• Afternoon → motivation to push through.
  
• Evening → lifestyle, shopping, inspiration.
  

 Mini takeaway: Segment first, write second. A subject line that feels personal always wins.

We like to believe readers open emails because they like us. Truth bomb: they don’t.

They open because something in the subject line made them feel.

It might be:

• Curiosity → “Wait, what’s this about?”
  
• Urgency → “If I don’t click now, I’ll miss it.”
  
• FOMO → “Other people know this — I don’t.”
  
• Relevance → “This solves my exact problem.”
  

Story check: A fitness brand ran two lines:

1. “New blog post: 10 workout tips.” (meh)
   
2. “Still skipping leg day? Here’s your fix.” (ouch, guilty)
   

Guess which one doubled their opens?

Mini takeaway: Emotion beats logic. Every time.

1. Curiosity-Based

Tease, don’t tell.

Examples:

• “You weren’t supposed to see this.”
  
• “The secret we almost didn’t share”
  
• “This email will self-destruct in 3…2…”
  

Story check: Buzzfeed built an empire on curiosity. “You won’t believe what happened next” might be cliché now, but the principle still works—open loops demand closure.

2. Benefit-Driven

Promise value upfront.

Examples:

• “Sleep better in 3 nights”
  
• “Double your leads this week”
  
• “Boost sales without spending more”
  

Think of it like a movie trailer. Show the best part without giving it all away.

3. Questions

A subject line that feels like a conversation.

Examples:

• “Still interested in this?”
  
• “What’s holding your team back?”
  
• “Want to grow your traffic?”
  

It taps into the brain’s instinct to answer.

4. Urgency & Scarcity

Perfect for launches or promotions.

Examples:

• “Last chance: doors close tonight”
• “Only 5 left — grab yours”
• “Sale ends in 4 hours”

Psychology 101: Deadlines drive action.

5. Personalization

Use names, actions, or anniversaries.

Examples:

• “Hey Sarah, this one’s for you”
  
• “You left something behind, Jake…”
  
• “Happy 1 year with us ”
  

When your inbox feels like someone actually knows you, it hits different.

6. List-Based

Lists = clarity + scannability.

Examples:

• “5 ways to beat burnout”
  
• “7 dinner ideas under 10 minutes”
  
• “12 subject lines that actually work”
  

Humans love numbers because they reduce overwhelm.

 Mini takeaway: When stuck, use numbers. Lists rarely fail.

Blank page? Try these classic copywriting formulas:

• AIDA (Attention, Interest, Desire, Action):
  “Hate Mondays? Fix it with this 3-minute ritual.”
  
• PAS (Problem, Agitation, Solution):
  “Tired of dead leads? Here’s the fix.”
  
• 4U (Useful, Urgent, Unique, Ultra-Specific):
  “Your 7-step holiday checklist (before Friday!)”
  
• FAB (Features, Advantages, Benefits):
  “Eco-friendly bottles that stay cold 24 hours.”
  

 Mini takeaway: Use formulas like training wheels until it feels natural.

Sometimes it’s one word that makes the difference.

• Curiosity: secret, hidden, reveal, sneak peek
  
• Urgency: last chance, ending soon, final call
  
• Emotion: cozy, inspiring, heartwarming
  
• FOMO: exclusive, limited, only for you
  

Example in action:

• “A little-known trick for better sleep”
  
• “Feel calm in just 60 seconds”
  
• “Only 3 spots left, don’t miss out”

• Writing like a robot: “Monthly Newsletter #12”
  
• Going spammy: “FREE!!! $$$ Win Big”
  
• Overusing emojis or ALL CAPS
  
• Making promises the email doesn’t deliver
  
• Going too long (mobile cuts it off anyway)
  

 Mini takeaway: Clarity beats cleverness.

• Welcome: “Hi [Name], we’re glad you’re here”
  
• Promo: “Flash Sale: Ends at midnight”
  
• Content/Nurture: “3 tips to beat procrastination”
  
• Re-engagement: “Still there? We’ve missed you”
  
• Transactional: “Your order is on the way”
  

Mini takeaway: Match line to email type — don’t overthink.

Here’s the thing: subject lines aren’t about being sneaky. They’re about signaling: “This email is worth your time.”

If you consistently deliver on that promise—clear, useful, human emails—your subscribers start trusting you.

And once you have trust? The subject line doesn’t have to work as hard.

So next time you sit down to write one, picture your reader at 7:30 AM with coffee in hand, scanning their inbox.

Will your subject line make them pause? Smile? Feel like you “get” them?

If yes—congrats. You’ve already won the inbox battle.