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How to Write Catchy Email Subject Lines

The best and worst open rates in Mailchimp.

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Writing catchy email subject lines is a big part of crafting the perfect email. People see email subject lines before they see anything else, so adding a catchy subject line for an email can be the reason someone opens your email.

So, how do you write a catchy email subject line? There are several factors to consider. For example, including certain words in the subject line may trigger spam filters, which means your emails won’t make it to inboxes. You also have to consider your email marketing goals and what kind of audience you’re writing for.

If you want to know more about writing catchy subject lines for email marketing, we’ve got you covered.

What is the subject line of an email?

The subject line of an email is the bolded line of text people see before they open an email. People use this subject line to determine whether or not your email is worth opening. If you choose a boring subject line or one that sounds like it could be a scam, people are less likely to open your emails.

Why is it important to have a good email subject line?

If you want to win at writing emails, you need catchy email subject lines that get people to open your emails. The subject line is one of the only parts of an email people see before opening that email, so your subject line can determine how many people read your emails. A catchy email subject line can draw attention and get readers to open your emails, but a poorly written subject line can send your emails straight to the spam folder.

Subject Line Data: Choose Your Words Wisely

Most people quickly scan the subject lines in their inbox before deciding which messages are worth their time and attention. With so much pressure on the subject line to entice the potential reader, we thought it would be interesting to see how much of a difference a single word can make in a campaign’s open rate, and what words can help your overall email marketing strategy and boost open rates.

To get some answers, we studied approximately 24 billion delivered emails with subject lines composed of approximately 22,000 distinct words. If you think that sounds like a lot of data, you’re right. We looked at subject lines both in general and within specific industries. Here’s a quick rundown of our criteria and approach:

  1. Investigate campaigns sent by users from the United States with tracking turned on in the past year. Only consider campaigns that were sent to 500 recipients or more, and only consider campaigns sent by users who have sent 10 or more campaigns before.
  2. For each campaign, calculate the open rate and standardize it using the user/list average open rate and standard deviation.
  3. Remove special symbols and convert subject lines to lowercase. For any given word, average the performance of all related subject lines and perform t-tests to identify high-impact words.
  4. For every subject line being tested, create flags for the presence of high impact words. Perform a correlation analysis on word presence to determine which words are frequently used together. Create additional flags for frequently used word combinations.
  5. Perform a linear regression analysis to estimate the impact each word has on standardized campaign open rates when accounting for all other tested words. Repeat this process on industry-specific data sets.

The numbers presented below are standard deviations from the mean open rate for a user/list. Words with positive impacts resulted in increased open rates, and words with negative impacts hurt those same rates.

Results for comparable word groups

The output of the regression analysis suggests that similar words often have similar impacts on open rates. Makes sense. Still, choosing the right words can result in higher open rates without altering the bottom line of your message. Again, to interpret these results, it’s important to know that a standard deviation is a standardized measurement of how much something deviates from the average value. One standard deviation for a user who tends to see large swings in open rates will be a higher percentage than it will be for someone with consistent open rates. That means choosing words wisely will have a larger impact on open rates for people with a higher standard deviation, while users with very consistent open rates can expect to see smaller changes.

7 tips for creating catchy email subject lines

Knowing how to write catchy email subject lines is imperative when it comes to email marketing. Check out these 7 tips for creating catchy email subject lines that will actually help get your emails opened.

1. Personalization works

Mailchimp’s merge tags let senders include first and last names provided by the recipients in campaign subjects or bodies. The impact this has on open rates has been debated before, but the consensus is that it’s positive. Our analysis found that personalized subject lines do indeed increase open rates. One of the most interesting findings is that, though the use of both first and last names in a subject is less common, it has the largest positive impact on open rates. Many of these campaigns seemed to contain highly personalized content.

Congratulations, *|FNAME|* *|LNAME|*

TED2014: Invitation to register for *|FNAME|* *|LNAME|*

Hi *|TITLE:FNAME|* *|TITLE:LNAME|*, please update your email preferences

Our analysis also showed that first name personalization is used much more frequently than last or full names, so we decided to see how the impact varied by industry. We focused on industries where the impact was significant, and found that there are several industries where use of the first name has a large positive impact. The most surprising finding, however, is that first name personalization has a negative impact on open rates for the legal industry.

2. “Free” isn’t guaranteed to help

Does including “free” in your subject line entice potential readers to open your message? It does, but not always. The next few charts show that although the impact of using “free” in a subject was found to be positive and statistically significant for certain industries, it was smaller when looking at all industries on a higher level. Interestingly enough, use of the word “freebie” was found to result in a much larger increase in open rates.

The high level results suggest that using “free” doesn’t have a large impact, but we investigated at the industry level to see if that result is consistent across the board. What we found is that people in the medical, retail, and travel industries should avoid using the word “free,” but restaurant and entertainment industries can certainly benefit from it.

3. People respond to a sense of urgency or importance

Needless to say, all of your emails are important. But there may be times when you feel like you need to communicate urgency and use a couple attention-grabbing words to let your readers know that your most recent message requires immediate attention. It works. Words like “urgent” and “important” resulted in open rates that were much higher than normal. Using words with a sense of urgency can increase your open rate, but use them wisely.

4. Announcements, invitations, and cancellations

Recipients are much more intrigued by announcements and event invitations than cancellations and reminders. It would appear that repeated reminders and cancellations don’t pique their interest quite as much.

It might make sense that people don’t open emails about cancelled events. Sometimes the title says it all. Still, we wanted to know if this impact was consistent across industries. What we found is that using “cancelled” in subject lines is negative whenever the impact is significant—except for in the restaurant industry, where recipients seem more interested in reading on.

5. Requests for donations are largely ignored

Throughout the analysis, words related to charitable actions and donations had a negative impact on open rates. Although all these words negatively impact open rates, choosing the right ones can mitigate the detrimental effect of donation requests. Of all the related words we studied, “donation” had the most negative impact. “Helping” had the best impact, though it can obviously be used in more contexts.

6. Frequently used word pairs often have significant impacts on open rates

During our analysis, we identified a number of word pairs that were frequently used. Sometimes two words can provide context that a single word can’t convey. We thought it would be interesting to see how some of these word pairs perform.

First and foremost, people love to be thanked. It’s also apparent that campaigns about current events, like natural disasters and political issues, have higher open rates than normal. And finally, it seems as though recipients don’t like to be asked to sign up for anything—and they really don’t like being told they’re missing their last chance to get something they’ve already been emailed about.

7. Capitalization can help slightly

While performing the analyses above, we looked at the impact of capitalization on open rates. The results were quite surprising. First of all, the use of an entirely capitalized subject line resulted in slightly higher open rates than usual for a given user/list.

We then cast a wider net to see what the impact of having at least one fully capitalized word was, and the effect was slightly negative. Both of these impacts, though small, are statistically significant. It’s worth noting that our methodology compares campaign performance to other campaigns from the same user to the same list. That means completely capitalized subjects result in higher open rates for senders that also use mixed-case subject lines.

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What does it all mean?

Many of these results can be applied to digital marketing campaigns in a straightforward way. For example, we can say that these things are likely to boost open rates:

  • Personalizing subjects
  • Marking appropriate emails as urgent
  • Thanking your recipients

We can also say that choosing words wisely when soliciting donations or reminding your recipients of upcoming events can minimize the number of unopened emails.

The more interesting takeaway, though, is that a single word’s presence can dramatically alter the likelihood that your readers will open your emails. The content of your message is really what determines which words you use, but with so few words in a subject line, each one matters quite a lot.

Catchy Email Subject Lines: FAQs

How do you write a catchy subject line?

Writing a catchy email subject line is all about making the most out of the little bit of space you have. As a general rule, you should try to keep your subject line under 40 characters to make sure the complete subject line is displayed. You can also ask open-ended questions in your subject line because they can help get readers interested. Of course, you want to avoid using any words that may trigger spam filters, including all caps, promotional language, and multiple exclamation points.

What are some good subject lines?

According to tests performed by Sumo, here are some of the best-performing email subject lines the company has used:

  • I was right – and that’s not good for you
  • 13 email marketing trends you must know
  • Before you write another blog post, read this
  • Are we still on for 12?
  • You don’t want FOMO do you?
  • We’re starting in 5 HOURS

Notice how these catchy email subject lines are somewhat open-ended. When people read these types of subject lines, they wonder what the email might be about, which gets them to open it up and investigate further. Keep in mind that your subject lines may vary quite a bit from these examples.

How do you grab attention in an email?

If you want to grab your audience’s attention in an email, start with a subject line that’s short and to the point. You can create a sense of urgency by mentioning an event or the date a sale is ending. Personalizing your emails helps people feel like you’re not strictly sending an email to promote your brand or product.

There are lots of little tricks you can use to write attention-grabbing emails. Just make sure you’re offering value in your emails and proofreading, testing, and rewriting to see what works best for your brand.

Use Mailchimp to write better emails

Writing catchy email subject lines is important if you want to humanize your emails. Take your time to figure out what types of subject lines are effective for your audience, and make sure you’re always tweaking and testing things. When it comes to email marketing, there’s always room for improvement.

Mailchimp’s tracking options enable you to take a similar look at your own campaign history. Maybe you’ll notice a recent email that asked for “donations” rather than “help,” or a crucial message that was labeled as “urgent” rather than “important.” Basic campaign stats can help you figure out what works best with your own recipients, and A/B split testing can automatically conduct experiments to see which words work for your subscribers, following through with the best choice.

Above all, just remember that one word can make a big difference.

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