The art of subject lines: increase open rates, maximize email campaigns

People send over 269 billion emails every day, and that’s only expected to increase over the next few years. Given that 111.1 billion of those are marketing related, your target audience’s inboxes are filled to the brim with offers and content.

What does this mean? The success of your email marketing campaign hinges on subject lines. If they contain words that trigger spam filters or don’t immediately grab the recipients’ attention as they scroll through their boxes, your actual offer or message will never be read.

But if you play your cards right, you can bypass filters and achieve higher open rates. All with just a few words.

Here’s how to get started.

Highly effective subject line ideas

The following “types” of subject lines routinely give marketers higher open rates, but don’t be afraid to mix and match or even go in a completely different direction. You can capitalize on pain points in a humorous way, get personal when you ask a question and offer information while creating a sense of urgency. But, don’t be afraid to try straight-forward subject lines like “Here’s your weekly newsletter.” Sometimes that style works wonders.

Capitalize on pain points

Think about the potential problem(s) your product or service helps customers solve. Then, use the subject line to address the issue and let them know you have a fix.

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Get personal

Use merge tags to include the recipient’s name, location, job title and/or company name in the subject line. Doing so increases open rates by up to 29%, no matter what industry you’re in.

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Ask a question

People love giving their thoughts and opinions. Open-ended, question-style subject lines capitalize on this, making the email feel like a conversation instead of a pitch.

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Give them some info

Let recipients know exactly what to expect by including a tidbit of information in the subject line. Note a stat pulled from the content you’re promoting or highlight what opening the email will teach them.

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Play up the urgency

Leverage humans’ innate FOMO by using the subject line to create a sense of urgency. Adding when the deal ends or noting limited supplies elicits just enough urgency to get customers to click.

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Be funny (or punny)

Humorous subject lines pique curiosity and make recipients wonder what other laughs they’ll get if they open the email. But, humor only works if you have a solid understanding of your base—if you don’t, it might fall flat.

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Create a cliffhanger

Take a cue from the entertainment industry and play on recipients’ natural curiosity. Teaser subject lines are irresistible to lots of people.

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Note a timely subject in your industry (like a new study), mention a trending phrase (just jump on Twitter for viral jokes and top hashtags) or allude to a current story. But, only focus on topics that tie into your brand; otherwise, you’ll just appear gimmicky.

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Power words

Marketers analyze billions of emails every year to find out what words and phrases generate the highest open rates. The list below includes some of the most effective, but make sure you’re analyzing your data, too. Your base might find certain keywords off-putting, even if most other companies’ see massive improvements in open rates using those same words.

power words infographic

Spam words

No matter how honest and helpful your email marketing tactics are, some phrases can get your emails sent straight to spam folders.

Note: The below words aren’t subject-line specific, and they aren’t a surefire way to trigger spam filters. If you include too many of one word or several of these words in one email (subject line and body), they’re likely to trigger spam filters. However, results depend on the specific filter, how solid your sender reputation is and the quality of your email list.

spam trigger infographic

Best practices

Writing winning subject lines takes loads of trial-and-error to find what piques your base’s interest the most. But as with everything, there are some best practices to keep in mind.

Watch the length. Super-long subject lines instantly look like spam to recipients and, depending on what they’re using to open emails, a longer subject lines could get cut off on screen. The sweet spot? Between 28 and 39 characters, according to MailChimp. If most of your recipients open emails on mobile devices, don’t exceed 30 characters.

Be 100% honest. Don’t make promises you can’t keep and don’t mislead readers as to what’s inside the email. Consumers are smart and easily irritated—blatant lies will get them to open your email once. And then promptly hit that unsubscribe button.

DON’T YELL AT PEOPLE!!!! Subject lines in all caps and littered with exclamation points make recipients feel subconsciously attacked. Find other ways to relay excitement, like including a firework or excited face emoji.

It’s OK to rework subject lines, but don’t reuse them. You put a lot of work into crafting a subject line that gave you huge boosts in open rates. But if you use the same one repeatedly, open rates will drop over time.

Test, test, test. Utilize your email marketing platform’s A/B testing tools to find out if your base likes short or long subject lines, they’re partial to statements or questions, they respond well to humor and so on. The more you test, the more data you have to work with.

Tools of the trade

Subject line testers check for potential spam triggers, give suggestions on word choice and even pinpoint what type of emotion the copy will provoke.

Emotional Marketing Value Headline Analyzer goes beyond standard marketing statistics. Instead, it scores the “emotional value” of the subject line, pinpointing words and phrases to determine if the subject line will light up the empathetic side of the brain or the intellectual.

Email Subject Line Grader and Subject Line score your copy based on word choice, length and best practices. And both give you advice for improvements.

Spam Check scans your entire email, including the subject line, to determine how likely it is that your carefully-crafted message will get flagged.

ISnotSPAM scans your email for potential issues and tracks your sender reputation so you can stay on top of problems.

Incorporate this info into your next email campaign, as well as these tips for writing conversion-focused copy, and you’ll be seeing a higher ROI on your email marketing in no time.


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