Your email subject line is the first thing readers see. If it fails, your campaign fails. You could write the best copy, design beautiful templates, and set up smart automations—but without a strong subject line, your email may never be opened.
This matters because 47% of people decide to open emails based on subject lines alone (source: OptinMonster). Poorly written subject lines mean lost revenue, wasted effort, and declining deliverability.
Key Takeaways
- Keep it short: Most email clients cut off after 40–50 characters. A clear, concise line makes your message scannable and mobile-friendly.
- Create curiosity: Tease value without revealing everything. This encourages readers to click through and discover more.
- Personalize smartly: Adding a name or product can increase opens, but only if relevant. Overuse feels spammy.
- A/B test your subject lines: Testing two variations shows you what resonates. It removes guesswork and improves future campaigns.
- Avoid spam triggers: Words like “Free!!!” or “Urgent” can hurt deliverability. Write naturally and add value instead.
In this article, you’ll learn proven strategies for writing subject lines, see real-world examples, and get tips you can apply today.
Why Email Subject Lines Matter
Your subject line acts as the gatekeeper of your message. Without a strong hook, subscribers may delete your email or ignore it completely. That means lower open rates, reduced click-through rates (CTR), and less revenue.
Think about your own inbox. Which emails do you open? Most likely, they’re the ones that spark curiosity, feel relevant, or promise value. The same psychology applies to your subscribers.
Strong subject lines also improve deliverability. Internet service providers (ISPs) track engagement signals like opens and clicks. Higher engagement tells Gmail or Outlook your emails belong in the inbox—not the spam folder.
How to Write Subject Lines That Work
1. Keep It Short and Punchy
Mobile dominates email. More than 60% of emails are opened on phones, where space is limited. That means your subject line should be under 50 characters whenever possible.
Short subject lines stand out in crowded inboxes. They also reduce the chance of your key message being cut off on smaller screens.
Example: Instead of “Check out our new fall collection with exclusive discounts,” try “New fall styles + savings inside.”
2. Use Curiosity and Urgency Wisely
Curiosity is one of the most powerful tools in copywriting. A subject line that teases information encourages readers to open your email to satisfy their curiosity.
Urgency, when used carefully, can also drive opens. Time-limited offers or “last chance” reminders motivate subscribers to act quickly.
Example: “You’re missing out on this deal (ends tonight).” This combines urgency with a subtle FOMO effect.
3. Personalize Beyond the First Name
Adding a subscriber’s first name can work, but true personalization goes further. Reference their past purchases, location, or interests for more impact.
This makes the subject line feel tailored instead of generic. Subscribers are more likely to open an email that feels like it was written just for them.
Example: “Nash, your favorite shoes are back in stock.” This leverages behavioral data instead of a plain “Hi Nash.”
4. Test, Measure, and Repeat
No audience is the same. What works for one brand might flop for another. That’s why A/B testing is essential in email marketing.
Send two versions of the same email with different subject lines to small audience segments. Whichever version performs best gets sent to the rest of your list.
One SaaS company tested “Your account needs an update” vs. “Don’t lose access—update today.” The urgency-driven version boosted opens by 21%.
Email Subject Line Examples You Can Steal
Sometimes inspiration helps more than theory. Here are a few subject line examples that have been proven to work:
- Curiosity-driven: “We need to talk about your cart…”
- Urgency-focused: “Last chance: 50% off ends tonight.”
- Personalized: “Your top picks for September are here.”
- Benefit-led: “Get more clicks with these email hacks.”
Each one is short, clear, and aligned with the value inside the email. That’s the winning formula.
Conclusion
Your subject line is the single most important factor in whether an email gets opened. A weak line equals wasted effort, while a strong one drives higher engagement and revenue.
Keep subject lines short, use curiosity carefully, personalize with relevance, and test everything. Each small improvement compounds over time to boost your overall campaign performance.
Now it’s your turn—pick one upcoming campaign and write two new subject line variations. Test them, measure the results, and keep iterating. Better subject lines mean better outcomes.
Frequently Asked Questions
What is the ideal length for an email subject line?
The ideal length is under 50 characters. This ensures the full line is visible on mobile devices. Shorter subject lines also make your message clear and punchy.
Should I use emojis in subject lines?
Emojis can increase open rates when used sparingly. They add visual interest and emotion. However, overusing them can feel unprofessional or spammy, depending on your audience.
Do personalized subject lines always perform better?
Not always. Basic personalization like using a first name may have limited impact. Contextual personalization—like product recommendations—usually performs better because it feels more relevant.
How often should I test subject lines?
You should A/B test subject lines regularly, ideally on every major campaign. Consistent testing builds a data-driven understanding of your audience’s preferences over time.
