The Do’s and Don’ts of Email Subject Lines

The subject line is one of the single most important factors for a successful email campaign. If it’s a good one, you see a high number of click-thrus. If it’s bad, no one will ever see the content in the email’s body that you worked so hard to create. The truth is, many of the attention-grabbing practices marketers use actually deter customers from opening emails. These tactics, like using too many exclamation points or words like “free,” can send your emails to the spam folder. So, how do you craft a killer subject line with such limited space? Here are some of the do’s and don’ts of email subject lines:



Use customer data to personalize messages. Start by using the customer’s name. You can also try segmenting messages by geographic location or by a customer’s previous purchases. Using customer data is all about making your messages more relevant, and not necessarily pretending you know your customers’ life story.

Keep it Short

Business Insider suggests eliminating filler words that don’t add anything to your message. Words like “Hello” and “Thanks” can go in the email body; there’s no use stuffing them in the subject line. Remember, you only have a limited amount of space to work with. Try to keep it at 50 characters or fewer. When the second half of your subject line gets cut off in recipients’ inboxes, the message is less effective. In fact, according to a study from Return Path, subject lines with 49 characters or fewer have open rates 12.5 percent higher on average than those with 50 or more.

Follow the 50/50 Rule

The 50/50 rule means you spend as much time writing the subject line and pre​-header as you do writing the rest of the email’s content. You may even want to write the subject line before you do anything else. Anyone who writes subject lines knows that saying something engaging with such limited space is more difficult than taking an entire page to do it. Don’t just go with the first subject line that comes to you. Work to make it better. Send test messages to colleagues to see what they think.


You may think you’re already doing that by reading this article, but there are digital tools than can help you improve your subject lines even more. Check out MailChimp’s Subject Line Researcher. If you’ve got some idea of what terms you’d like to use, you can plug them into the tool and MailChimp will show you how those terms and similar ones performed in previous campaigns. It’s pretty nifty, and it’s free!

Related Content: Extend your reach today with Stirista email append, hygiene, creative and deployment services!



Your subject lines should directly reflect the content of the message. That may sound boring, but trust us, it works. Don’t waste time writing something too creative because the best subject lines are more descriptive than flowery. Most importantly, if you mention a deal or promotion in the subject line, you better follow through in the message itself.

Use Caps Lock

Sure, capital letters stand out. The problem is that they stand out in the wrong way. According to MarketingProfs, writing subject lines in CAPS LOCK is like yelling at your customers. On top of that, adding exclamation marks or other symbols could send your message straight to the spam filter.

Ignore the Pre-Header

The pre​-header space is vital. In many email providers, the first line of the email shows up as a preview in the inbox screen. In other words, it’s an extra chance to gain a click-thru. Think about how the subject line and pre​-header space work together to communicate your message. Don’t repeat any information in these spots and don’t waste the opportunity with something like, “Click here to view this email in your browser.”

Act Like You’re Already Best Friends

Personalization is fine as long as you’re respectful. Doesn’t it drive you crazy when marketers get too cozy with their email language right off the bat? Sending a message that says, “Is it something we said?” can be irritating to many customers. As Act-On notes, this category includes sneaking in “re:” or “fwd,” or any other phrases that make it seem like you’re already corresponding.

For something so short, writing email subject lines is hard. The first step in writing a subject line that increases click-thrus is respecting the journey to get there. Take length, wording and personalization tactics into account. Leave no stone unturned. Soon you’ll be on your way to mastering the art of the subject line.

About the author

Stirista began as an ambitious project from an apartment in San Francisco. But as office space expanded, so did our client base. After a few short years, we have worked with the largest healthcare insurance provider in the world, the biggest telecommunication company in the US, and some of the most prestigious universities in the country. We are on the preferred vendor list for a handful of Fortune 500 companies, with three of the ten largest companies in the world turning to us for...

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