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How to Write Email Subject Lines That Get Opened (Based on Research)

Does writing an email subject line make you sweat?

Knowing it can make or break your email campaign sure puts on the pressure, doesn’t it?

I’m about to make it easier for you to write a winning email subject line. I’m going to share research findings about high-converting email subject lines — the ones that get the email opened and read.

Researchers have tested at least four elements:

  • The use specific words
  • Personalization
  • Length
  • Reader connection

Read on to learn how email campaigns can be affected by these elements and how you can use them to get better results.

1. Use words that trigger email opens and clicks.

Words are the building blocks of your email subject lines. Single words can trigger images, emotions, attitudes and memories. Words are powerful.

Are some words more likely than others to get your subject lines opened?

Research suggests exactly that.

In 2013, Adestra released a study of email subject lines from 2.2 billion emails in an attempt to identify specific words and phrases that get both higher open rates and higher click rates.

The study covered various sectors, including B2B, B2C, nonprofit, retail and e-commerce.

Across all sectors, the email subject lines with the following words and phrases had open and click rates that were higher than average:

  • Free delivery
  • Sale
  • Alert
  • News
  • Video
  • Win
  • Daily
  • Weekly

As you can see, benefit-oriented words like “free delivery” and “sale” do well in email subject lines. Words conveying urgency or time sensitivity also get emails opened. The success of “video” in email subject lines is probably due to the increasing popularity of online videos; more and more people are viewing them.

In contrast, some words in email subject lines tend to lower open and click rates:

  • Free
  • Only
  • Learn
  • Report
  • Today
  • Webinar
  • Monthly
  • Get
  • Register
  • Don’t miss
  • Re:
  • Fw:

The low performance of these words suggests email users have gotten smart about identifying hype. Some of these words have become overused in spam, especially “free,” “Re:” and “don’t miss.”

It’s interesting that call-to-action words, such as “get” and “register,” generally did poorly in email subject lines.

Benefit-oriented words, provided they’re not hype-y, do better in email subject lines than calls to action.

The Adestra study presents different findings for specific sectors, so it would be worth your while to get the full study to learn about sector-specific findings relevant to you.

In another study, words referring to movies and songs appear to lift email open rates.

In an analysis of 3.7 million emails, Retention Science found that subject lines with a movie title or a song lyric have an average open rate of 26 percent compared with only 15.8 percent for subject lines without these cultural references.

When it’s relevant, and when you think it will resonate with your readers, mentioning a movie or a song in your subject line will probably get your email opened.

BTW: Check subject lines of these welcome email examples or these promotional email examples.

2. Personalize.

In “How to Win Friends & Influence People,” Dale Carnegie says “a person’s name is to that person the sweetest and most important sound in any language.”

Does personalizing with the reader’s name make email subject lines more effective?

Research says the answer is yes.

Retention Science analyzed 260 million emails and 540 campaigns and found that personalization did increase email open rates. Subject lines with the recipient’s first name had an average open rate of 18.3 percent, while subject lines without a first name had an average open rate of 15.7 percent.

Similarly, MailerMailer found personalized subject lines had an average open rate of 12.9 percent compared with 9.8 percent for subject lines without personalization.

Still not convinced? In yet another study, Experian found personalized subject lines had 26 percent higher open rates than nonpersonalized ones. The lift was highest for travel companies.

What’s more, Experian found that 70 percent of brands do not personalize their emails. If your practices mirror those brands, personalization is an element you should definitely look at.

3. Keep the subject line either very short — or very long.

Now let’s look at the length of your subject line. Can it make a difference?

According to Retention Science, email subject lines with six to 10 words had the highest open rate (21 percent), followed by subject lines with five or fewer words (16 percent). Subject lines with more than 10 words performed worse as they got longer.

A number of other studies had similar results. For Return Path, the sweet spot was less than 49 characters (12.5 percent higher open rates and 75 percent higher click-through rates).

For Adestra, however, the effect of email subject-line length on open and click rates wasn’t as straightforward.

Adestra found that email subject lines had to be either very short (less than 30 characters) or very long (100 characters and longer) for open, click-through and click-to-open rates to be optimized.

While this finding may support longer email subject lines, keep in mind how many of your subscribers access emails on mobile devices. As we mentioned (https://unbounce.com/email-marketing/subject-line-strategie-that-increase-your-open-rates/), because mobile devices truncate email subject lines, you need to consider length and word order.

4. Connect with your reader.

Finally, let’s look at general principles that work when writing subject lines.

Marketing Experiments studied over 100 successful email subject lines and concluded that they worked because they built an immediate connection with the readers.

You can create this immediate connection through one of two approaches:

Connect to an internal issue

By “internal issue,” Marketing Experiments is referring to a need or a problem your readers have.

Examples of internal issues include the following:

  • Lack of resources, such as time, money or help
  • Unmet expectations, whether at work or in the family
  • Inability or inadequacy of skills
  • Operational difficulties, such as lack of usability
  • Fragmented perspectives, such as ignorance or misunderstanding

When your subject line promises a relief or a solution to any of these issues, your email will get opened and get a higher click rate.

For instance, the following subject lines outperformed similar ones that didn’t connect with an internal issue:

“[Company Name]: Now only 2-meal minimum order”

“Free Unlimited Access to [Newspaper] Online”

“Reach 120,000 Physicians Through Social Media”

Connect to an external event

External events are activities, whether in the recent or distant past, which have occurred in your subscribers’ lives. For example:

  • Action or behavior
  • Conversation
  • Single exchange (completed or abandoned order)
  • Cancellation (of a membership, contract or recurring transactio)
  • Service interaction

Subject lines referring to such external events make the emails more meaningful to the recipient. These emails become part of a subscriber’s “story.” As a result, the emails are opened more and get higher click rates as well.

Here are a few examples of subject lines that connect to an external event:

“[Name], Your Account Information Is Ready to View”

“Did you forget your [Bank Name] online username or password?”

“Subject lines that fail – Recent research reveals why your emails don’t get opened”

These subject lines work, because they connect with your readers’ lives. This shows the power of crafting targeted email campaigns and subject lines based on subscribers’ actions.

Here are highlights from the study

Putting Everything Together

These research findings give you a starting point for writing email subject lines that are most likely to work with your subscribers. Use the research to form hypotheses about the types of subject lines that may get higher opens and click rates.

These are not hard-and-fast rules.

Take into account that these studies were conducted in different sectors and markets, and even with different types of mailing lists — current customers, prospects, lapsed subscribers, etc.

The best way to discover what will work with your readers is to test. For inspiration, here are some examples of A/B split tests of email subject lines.

And when you test, realize it’s not enough to look at open rates; you must also look at click rates. You’re not after hype-filled subject lines that get opened out of curiosity but are then quickly abandoned because they’re irrelevant. Align subject lines with the content of the email to drive click-throughs.

Now that you’re familiar with recent research on email subject lines, how do you plan to improve the subject lines you write? Which elements are you going to test in your campaigns?

Alexis Rodrigo is a copywriter who helps businesses and organizations create content that converts audiences into leads, prospects and customers. Connect with Alexis on Twitter.

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