How to Craft Email Subject Lines That Boost Open Rates

A lot of skill goes into writing irresistible email subject lines that boost open rates—more than many people might realize.

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Think about the tens (if not hundreds) of emails you get every day. Some of them you don’t even bother opening, and it’s not because you haven’t read the body of the email. It’s because whatever is in the subject line isn’t compelling enough for you to even feign interest.

But then there are emails that you can’t wait to open, and the reason for that is because something — again, that subject line — has lured you in.

Email statistics reports show that the average person receives 100 to 120 emails per day, and sends about 40 each day. Yes, that is a lot! Moreover, at least 33% of people make the decision to open an email solely based on the subject line.

What is it about the subject line that makes you want to spend valuable time on an email?

There’s a lot of craft that goes into it, more than many people might realize.


Key Factors to Craft Irresistible Email Subject Lines


Irresistible subject lines all start with knowing who your audience is and using the right words to appeal to them. Obviously, therefore, the choice of words you use when crafting your email subject lines matter a lot.

To increase open-rates, there are common words and phrases you should consider including in your subject line. On the other hand, there are words you should avoid when crafting your subject lines.

Among the good words to include in email subject lines are “you," "your,” and "names." Other power words to inspire a sense of urgency and excitement are “free delivery,” “special" "offer,” “new,” “updated,” "daily," “alert,” and “news.”

Words to generally avoid in your subject line include: “guaranteed,” “report,” and “earn.”

Additionally, industry reports suggest that the more words you use in your subject line, the lower your open rates will be. You'll get fewer opens when you use more words. 

That means your best best is to use a few words that have a short number of characters in your email subject lines. Ideally, use 3-5 words in your subject line to boost your email open rates.

Other factors to consider when crafting your subject line besides choice and length of words are personalization and design of words like title case and caps.

Personalize your email subject lines as much as possible by referring to the recipients by their names, mentioning their birthdays, previous purchases, and their location. The more personal the email, the more likely it is to get opened.

When it comes to the design of words, using title case instead of sentence case or all lower case in an email subject line. This is an authority badge for the sender that can increase open rates. 

Don't forget to play around with numbers, punctuation, and even emojis in your email subject lines. Where applicable, include numbers, exclamation marks, percentages, and at least one emoji in the subject line.

For example, "Get 50% discount today!” is more appealing than "Get a discount today."

More importantly, A/B test or split test different email subject lines to discover which combination has maximum effect on your subscribers and brings the best results. Test everything, including the type, length, and design of words you use. For example, test subject line design not with your typical graphics and colors only, but with all caps, emojis, punctuation, and spacing too.


Tips to A/B Test Email Subject Lines


A/B testing may seem like a chore to the uninitiated, but running these tests help you get to know your audiences better and provides valuable insights you can use to boost open rates.

A/B test the combinations you use in your email subject lines to find the clear winner and learn what works and what doesn’t. 

Here's an infographic that walks you step-by-step through the art of crafting and A/B testing subject lines so you increase your email open rates:


Jessica Bennett is a writer, editor, and novelist. Her clients span a number of industries, and she's written blog posts, product descriptions, articles, white papers, and press releases— all in the name of inbound marketing. She's proud to be Inbound Certified.