How to Write Email Subject Lines That Make People Click

June 10, 2025

In the constantly changing world of digital marketing, crafting the perfect email subject line has become a make-or-break moment. Regardless of how good your email content is, if the subject line does not trigger curiosity or instant value, it will get buried in the inbox, unopened and possibly deleted.

With attention spans shrinking and inbox competition rising, the art of writing compelling subject lines is more important than ever. In this blog post, we'll share actionable strategies for you to boost your email open rates, encourage engagement, and convert your subscribers, starting with the subject line.

Why Email Subject Lines Matter More Than You Think

According to OptinMonster, 68% of email recipients decide whether to open an email solely upon viewing the subject line. This means that if you're not optimizing this short but powerful piece of text, you might be leaving potential leads and revenue on the table.

The subject line is your digital elevator pitch: it needs to be interesting, relatable, and actionable in seconds. At iMarketo, we work with brands every day to put together high-converting email campaigns, and one of the first things we analyze is subject line performance.

1. Understand Your Audience First

A great subject line is built on an understanding of your audience. Knowing what your subscribers care about, what pain points they’re facing, and what motivates them to act is essential for crafting messages that resonate.

How do you best get the insights?

• Analyze past open rate trends to identify what kinds of subject lines worked best
• Segment your list by behaviors, demographics, or even by prior contact
• Use surveys, polls, or other methodologies to learn directly from your audience, their needs, and ideas

Example: Instead of saying:

• “Big Sale This Weekend”

Say:

• “John, Don’t Miss Your Exclusive Weekend Offer”

This personalized approach shows the reader that the email is relevant to them, not just another message.

2. Keep It Short and Scannable

Most people access their emails on mobile, where subject lines can get cut off after 40–50 characters. If your message is too long, your most compelling words may never be seen.

Best practice:

Keep subject lines under 9 words or 50 characters where possible. A good structure is to lead with your most important information.

Examples:

• "Your Free Template is Ready"
• "Limited Time: 25% Off Ends Tonight!"
• "Why Your Ads Are Not Converting"

Short, punchy subject lines are easier to read and more likely to spark curiosity quickly.

3. Focus on Clarity Over Cleverness

Clever subject lines may seem like a good idea, but if they’re too vague or confusing, they can hurt your open rates. In most cases, clarity beats creativity.

Your subscribers don’t want to guess about the email - just tell them what they’ll gain by opening it.

Example: Instead of:

• “Ready to Level Up?”

Do:

• “Download your 2025 Growth Strategy Plan.”

When in doubt, be clear and relevant.

4. Create Curiosity—But Don’t Clickbait

One of the most significant ways to increase your opening rates is by creating curiosity in the audience. However, there's a fine line between curiosity and clickbait. If your subject line promises something the email doesn’t deliver, it can damage your credibility and lead to unsubscribing.

Effective curiosity examples:

• “We Doubled Our Traffic by Doing This One Thing”
• “What 80% of Marketers Miss About Conversions”
• “There’s a Strategy You Haven’t Tried (But Should)”

Curiosity works best when backed by real value inside the email.

5. Use Numbers and Lists for Exactness

Subject lines using numbers tend to perform better because they communicate order, value, and clarity. Numbers also attract attention and make content easier to consume.

Examples:

• "5 Email Marketing Hacks to Increase Your Open Rates"
• "3 Tools You Should Be Using for Content Marketing"
• "7 Proven Subject Line Formulas You Can Use Today"

Numbers also provide clear expectations as to what is in the email.

6. Add Personalization Where It Makes Sense

According to Campaign Monitor, a personalized subject line – a recipient’s name or referring to previous behavior – can lead to higher open rates, up to 26%. But personalization should feel organic and applicable, not forced or creepy.

Examples:

• "Sarah, Your Weekly Report is Ready."
• "We Found These Deals for You"
• "You Left This in Your Cart – Still Interested?"

Avoid overusing first names if it doesn’t enhance the message. The goal is relevance, not novelty.

7. Create a Sense of Urgency

Urgency incites an action. When people think they will miss out on something, they're more likely to open the email right away. Use time sensitive language to help facilitate quicker clicks.

Examples:

• “Final Day to Save 40%”
• “Only a Few Spots Left—Reserve Yours”
• “Sale Ends at Midnight Tonight”

Urgency is most effective when it’s real. If your deal doesn’t actually expire, don’t say it does.

8. A/B Test your subject lines  

There is no way for even the most experienced marketers to know for sure what the subject line is going to yield better results. That's why you need to do A/B testing.

Most email platforms will let you A/B test two (or more) versions of your subject line on a smaller segment of your audience. Once you have a winner for your subject line, the platform will automatically send this to the rest of your subscribers.

What to A/B test:

• Subject line length
• Questions vs. statements
• Personalized vs. non-personalized
• Urgency-focused vs. benefit-focused

By regularly testing, you’ll discover what your audience responds to—and what to avoid.

9. Don't skip the preheader text

The preheader text is a short summary that appears below the subject line in most inboxes. I think of it as a subheadline to your subject line.

Tips for effective preheaders:

• Don't reiterate the subject line
• Dig deeper into what is included in the email
• State the value (or next steps)

Example:

• Subject Line: "Your Free Social Media Calendar"
• Preheader: "Plan a month's worth of posts in less than 10 minutes!"

Together, the subject, and the preheader text should give a strong reason to click!

10. Match the Subject Line in the Email

One of the biggest principles of email marketing is to deliver on your promise. If your subject line offers a free guide, then ensure the guide can be accessed easily. If your subject line offers a story, or case study, then make that the centerpiece of the email.

Aligning expectations leads to better engagement and higher trust over time. Misleading subject lines may drive short-term openings but damage long-term brand reputation.

Conclusion

Writing subject lines that people want to click is part art, part science. You'll need to have an incredibly good understanding of your audience, continuous testing, and a clear indication of value. If you follow the tips outlined above — along with ongoing optimization— you're going to start seeing improved opening rates, a more resonant brand story, and drive more results from every campaign.

At iMarketo, we pride ourselves on building data-driven email strategies that obtains attention and drives revenue for businesses. From subject line A/B testing to full-funnel automation, we’re here to help you transform your email marketing.