As a portion of your whole email campaign, your subject lines may seem like a small part, but they’re actually quite important. Subject lines act the gatekeepers to your emails; the one snippet of copy your subscribers use to determine whether they’ll read your email or just click delete (or worse: “Mark as Spam”).

Your beautiful design, your killer products, your generous offers… all of these things are wasted if your subscribers never open the email. So it’s important to craft your subjects carefully in order to get the best possible ROI from your email marketing efforts.

If you want to boost your open rate, you’ll need to know how to craft irresistible subject lines.

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Subject line techniques

These copywriting techniques will help you craft powerful subject lines that compel your subscribers to click. Don’t try to cram each of these techniques into your subjects, just use one (maybe two) that are most appropriate.

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1. Segment and personalize

People don’t want to read emails they don’t care about. If you burden your subscribers with content that doesn’t appeal to them, they’ll assume your brand isn’t for them and unsubscribe.

Segmenting your list is an important way to send your subscribers only the content they want to consume. If a shoe retailer blasts an offer for women’s high heels to its entire list, its male subscribers might scratch their heads in confusion and probably unsubscribe.

Segmenting your list also improves your open rate because your subject lines can more closely relate to the email’s content. Instead of using a generic subject like “10% off shoes,” you can target specific customers with something more descriptive, like “Great deals on women’s sandals for summer beach days.”

You should segment your subscribers by demographics, interests, and buying habits so you can cater their specific emails – and their subject lines – according to their preferences.

Furthermore, personalization has a number of other benefits you shouldn’t ignore.

2. Appeal to curiosity

Your subscribers will open your emails if you can appeal to their natural curiosity and pique their interest. Try to begin coy, humorous, and enticing. This so-called “curiosity gap” is the same technique employed by sites like Upworthy to drive explosive growth.

That said, don’t be so mysterious that your subscribers have no idea what’s in the email. If the subject line doesn’t mean anything to your readers, they’ll just ignore it. Data from MailChimp shows that it’s important to describe what’s in the email without being so creative that subscribers aren’t at all sure what to expect if they click.

Example: “You won’t believe what we over-ordered”

One way to stimulate curiosity is by asking a compelling question. It’s especially useful if the question is relevant to your subscriber’s goals, dreams, problems, or preferences.

Example: “What did you get her for Valentine’s Day?” or “What’s in your winter wardrobe?”

3. Motivate with scarcity and urgency

Scarcity and urgency are powerful marketing techniques that make email subject lines irresistible. Words like “urgent” and “important” lead to much higher open rates.

Urgency is an excellent way to encourage your readers to click right now by overriding their tendency to decide “I’ll check that out later.” Just make sure there’s some actual urgency, even if you have to manufacture it yourself. Don’t push urgency where there isn’t any.

Example: “Summer deals end tomorrow”

Scarcity is when you let a customer know they’re about to miss something. The fear of missing out is especially powerful. This technique is often used in conjunction with urgency.

Example: “Only six summer styles left in stock”

4. Hawk your discounts, offers, and free stuff

Don’t be afraid to put prices, discounts, and deals right into your subject lines. In other industries, this type of forwardness could be considered rude, but as an eCommerce store, people expect this type of behavior. They know how the relationship works.

Plus, people like to investigate deals even if they don’t plan to make a purchase. If your email advertises a discount, offer, or free gift, put it right in the subject line.

You might also find it helpful to pair this technique with another technique, like personalization, urgency, or scarcity.

Example: “Maggie, take 10% off our summer line before we run out”

5. Keep your subjects short

Interestingly, there’s no correlation between subject length and open rate. MailChimp studied 12 billion emails and learned open rate changes very little as subject characters rise.

Of course, this data is an average of many emails across many industries. Your customers may have a preference, which is why it’s smart to A/B test your subject lines.

Nevertheless, it’s good to trim your subjects to only what’s essential. 67 percent of emails are opened on mobile devices where there’s only about 50 characters worth of space. Plus, people scan their inboxes quickly (especially their promotions folder), so it’s best to keep your subjects concise and use simple language.

6. Relate to something popular

Aligning your subject line with something popular (a trend, a meme, a news story, etc.) can help establish your brand as something real and relevant that’s worth paying attention to. It also helps to connect with something that may be on the top of your customers’ minds.

For example, if you know your customers are football fans, you might send out an email advertising a special deal or specific set of products for Super Bowl Sunday. You can even segment by geographic location so that customers get location-appropriate messaging using local slang. For last year’s Super Bowl, perhaps you’d send people in Philadelphia email with the subject line, “Got that jawn yet for the big game?” Whereas everyone else might receive the more generic, “Do you have the right gear for the big game?”

Be careful, though, as this strategy can sometimes run afoul of someone else’s trademark. The NFL owns the trademark for “Super Bowl,” and they vigorously defend against non-official sponsors using it. (That’s why our example uses “big game” instead.)

7. Be honest about what’s inside

This tip doesn’t necessarily apply to a single email, but it’s important to consider in regards to your entire email marketing program.

Your subject line is a promise to your reader. The email’s content should deliver on that promise. If you trick your subscribers to open emails by making false promises, they’ll learn to ignore your emails, and eventually mark you as spam.

If you’re only offering a 10 percent sale, don’t call it “the biggest sale ever.” Don’t call your products “exclusive” if your customer can buy them on Amazon. You get the idea.

8. Start with action verbs

In a way, subject lines are calls to action. Their single purpose is to compel the reader to click into the email. It can be useful to craft your subject lines with action verbs like you would any call to action.

Here are some examples:

• “Get your new swimsuit”
• “Don’t wear last year’s styles”
• “Meet your new jeans”
• “Save big on phone accessories today”
• “Get a head start on summer”

9. Avoid words, phrases, and styles that look like spam

As of September 2017, spam accounts for nearly 60 percent of all email traffic, which is why 69 percent of email recipients report email as spam based solely on the subject line. These days, people are super sensitive to spam in their inbox.

It’s nearly impossible to claw your way back into someone’s good graces once they’ve marked you as spam, so avoid using anything in your subject line that makes the recipient consider it as spam. That includes…

• All capital letters
• Lots of exclamation points
• Special characters (or obvious attempts to avoid certain words)
• Spelling mistakes
• Too many emojis (some are fine – even welcome depending on your brand’s personality – but don’t go crazy)

Additionally, avoid common spam words. They make readers cringe and most email clients filter them straight into spam folders. This chart shows you just a few, but read our post on email deliverability to learn more.

Pick and choose your techniques

As you’ve probably noticed, you can’t use all of those techniques in the same subject line. There’s no way to ask a question and use an action-verb, for instance. Choose the technique(s) that are most appropriate for your email’s content and test to uncover what works best. There are also subject line tools that purport to rate the expected effectiveness of your subject lines or offer suggestions for high performing ones.

Good subject lines lead to email engagement and sales. Bad subject lines can cost you a critical form of communication with your customers. Follow this advice and you’ll send out subject lines your subscribers can’t help but click.

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