5 Tips to Create a Killer Subject Line

Mallory Mongeon | 2014-01-29T11:51:03+00:00 | email on acid logo

You never get a second chance to make a first impression.

This couldn’t be truer when talking about email marketing, or more specifically, about subject lines. According to an analysis of 5 million emails from Baydin, an email management service, the average email user gets 147 messages per day and deletes 71 (48%). As your subscriber’s inbox fills with mail, they become more and more trigger happy. Soon, they’re jamming that delete key without a second thought.

That’s where the subject line comes in. Your subject line is your first (and perhaps only) chance to make an impression. For this reason, your subject line’s job is to stop readers in their tracks. So that begs the question, what does a fantastic subject line look like? How long is it? Is it personal or professional? What must it communicate? Crafting solid subject lines is part art and part science, so there are no hard and fast answers to these questions. But don’t worry.

We’re here to steer you down the right path, with these 5 tips on crafting captivating subject lines.

  1. Manage Your Readers’ Expectations
  2. Steer Clear of These 3 Words
  3. Localization vs. Personalization
  4. How Long is Too Long?
  5. Make It Actionable.

1. Manage Your Readers’ Expectations

I’ve adopted, “Manage my expectations,” as my new motto. This is a saying that is a favorite of our CEO, John Thies. This is a very important request; unrealistic expectations can lead to disappointment and even anger, but fulfilled expectations lead to happy customers, as well as higher open rates and more sales.

In order to craft a subject line that will have some kick to it, you need to be able to put yourself in your readers’ shoes. Your readers are getting flooded with SPAM on a daily basis and sometimes don’t have the time to separate the wheat from the chaff. That’s why you, as a marketer, need to stay away from ambiguous teasers and tongue-in-cheek titles.

A 2011 case study conducted by AWeber Communications found that a clear subject line gets 541% more clicks than one that’s clever. Clarity is essential to your open rates. Take a tip from MailChimp when they say, “When it comes to email marketing, the best subject lines tell what’s inside, and the worst subject lines sell what’s inside.”


This is a screen capture from Aweber’s results when they tested whether clear subject lines would outperform clever subject lines.

2. Steer Clear of These 3 Words

MailChimp recently ran a campaign where they tried to uncover the best practices in writing email subject lines and came up with some real gems. For this study, MailChimp analyzed the open rates for over 200 million emails. One aspect that MailChimp studied was if there were any words to avoid when writing subject lines.

Many marketers fear using the word “free” in their subject. They recoil from using this phrase because they think “free” will tank their open rates and throw them into the SPAM folder. However, that’s not totally true. SPAM filters can be triggered for a variety of reasons, but specific words are rarely the culprit. Content-based filtering has fallen by the wayside as blacklisting has become more popular.

You might not get thrown in the SPAM bin, but choosing the wrong wording can act as a repellant to your readers, so choose your words wisely. The study did uncover words you should stay away from in your subject lines and guess what… free wasn’t one of them. Check out the three words MailChimp suggests you avoid:

  • Help
  • Percent off
  • Reminder


These are results from MailChimp’s study.

It’s not all bad though! MailerMailer did find the most popular words you should use as well. The study indicated that words or phrases that expressed relevance (newsletter, weekly updates), persuaded (party, sale, free), or specified time sensitivity (deadline, day, weekend, hours) were the best.

3. Localization vs. Personalization

In a recent Econsultancy survey 94% of businesses stated that personalization is critical to their current and future success. However, according to Stanesby, too much personalization in email (such as using the recipient’s name in the subject line) can have a detrimental effect.

MailerMailer reported this trend as well. Their report showed that emails that were not personalized saw an average open rate of 11.5% and those with the subject line personalized saw an average open rate of only 5.2%. When it comes to personalization in your emails, you need to find a happy medium. That’s where localization comes in.

Localization in subject lines is used when targeting an email blast by location. The mega retail store, Target, made good use of this tactic when they tested localization in promotional emails. They did this by identifying which Target stores were close to their recipients listed address. The email sent to them featured the name of the subscriber’s local store in the subject line, as well as that store’s telephone number and store-specific links.

A great example is the email blast Target sent out on May 31st, with a subject line that read, “New this week: Check out the deals at your Edina Target Store.” Adding this small detail will make recipients feel like the email is that much more relevant to them. MailChimp supports this notion as well, as they have seen localization (such as including a city name) improves open rates big time.


These are results from MailChimp’s study.

4. How Long is Too Long?

The general rule of thumb in email marketing is to keep your subject line to 50 characters or less. Why should you care? Because of mobile devices. Adobe reported that 79% of smartphone owners use their smartphone for reading email. On most mobile devices, if you exceed 50 characters your subject line will be cut off. If you’re not optimizing your subject line length, you’re missing out on a big chunk of cheddar.

Now let’s get down to the nitty gritty. Is there an exact number of characters that is the most optimal for conversions? In short, no but you can make an educated guess! Data from MailerMailer indicates that the sweet spot for the highest open rates is somewhere between 4 and 15 characters. Check out the chart below to see how brevity is the way to get your message across.


This is a screen capture from MailerMailer.

5. Make It Actionable.

When formulating your subject line, there is one question you MUST ask yourself, “does the reader know what he or she should do in the email?” Your readers should ALWAYS know what their next step is. If your subscriber is confused by your subject line, their eyes will just skim right over your email without understanding that an action is required on their part. You need to use action words that will spur your reader to open your email in order to drive your sales forward.

Creating a sense of urgency is another great way to make your subject lines actionable. You should use attention-grabbing words that imply time sensitivity so your readers know that your message requires their immediate attention. MailChimp reported that words like “urgent” and “important” resulted in open rates that were much higher than normal. The shorter the amount of time that recipients have to act, the more compelled they will feel to do so.

For example, take a look at a test a company called Email Aptitude ran when promoting free shipping for a shoe sale. Both subject lines mentioned that there was free shipping but the second subject line gave a deadline for when the promotion would expire. This simple tweak made a 5.25% difference in the open rate which can make or break a campaign.


This is a screen capture from Email Aptitude.

Your words matter, so choose them wisely

Before you can know if your subject line will work for your readers, you must know your audience. Every industry is different when it comes to what motivates them and that is why you must A/B test your way to a better subject line. According to WPCurve, a simple A/B subject-line test they did yielded an increase of 28% in clicks!

With over 1.9 billion non-SPAM emails being sent every day, what are you doing to uncover what really resonates with your audience? If your subject line doesn’t captivate your reader, one of the other 200 emails they see that day probably will.

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