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Email Subject Lines: 8 Secret Steps To Increase Click Rate

by Nedim Talovic · Updated 22 Feb 2022}}

You’ve probably heard so many times that email marketing is still the best email marketing channel because of its ROI and many other reasons as well.

Indeed, you shouldn’t have doubts about investing in it, but if you’re still not convinced I suggest to reading more about email marketing.

An average business user sends and receives a lot of emails and according to Radicati, that number is 123 emails a day.

Emails per user stats

In writing effective emails, subject lines are the first step, and they should be attractive, eye-catching, curious, and much more.

Therefore, in this blog post, I’ll show you how to write subject lines to increase your open & click rates.

Here are the steps you can take to improve email subject lines.

  • Segment Subscribers
  • Understand Psychological Principles
  • Include Numbers
  • Use Magnet Words
  • Consider Subject Line Length
  • Use CoSchedule’s Headline Analyzer
  • Email Subject Line Keyword Checker
  • Track Your Results

Let's see in more details.

#1 Segment Subscribers

What segmenting customers have anything to do with subject lines? A lot more than you think.

Segments are groups with certain similarities and based on that, some subject lines will trigger better than others. Also, you should consider using a good software for segmenting your contacts

Customer Segments

Source: optimoveblog

For example, let’s say you segment people by age and then target ones who were born in 1987 - they will be 30 years old in 2017.

In the subject line, you can offer presents for this special year for them.

This way segments allow you to create more personal subject lines, which will result in better open rates. The more data you collect, the more segmenting options you’ll have.

#2 Understand Psychological Principles

Human psychology is your playing card in writing emails. This especially stands for B2C businesses, but it’s also very applicable in B2B’s.

You’ll notice that in every quality text about CTA’s (Call-to-Action) the psychological moment is mentioned, including the psychology of colors, numbers, or phrases.

Why am I bringing this up?

Because subject lines are nothing but a call to action of its kind. Here are some general rules about people's behavior that you can use in writing subject lines:

  • Fear of missing out is irresistible
  • Curiosity is humans natural desire
  • Humor is the best trigger
  • Vanity is part of us
  • Greed is part of us (we’re unwilling to admit but it’s true)

#3 Include Numbers

When you put numbers in email subject lines you are going more specific and that’s always a good thing because people don’t have time to explore what’s inside.

Numbers in subject lines

The test from Marketing Experiments clearly shows how numbers in email subject lines can increase open rate & click rate.

Among dozens of emails in recipient's inboxes, subject lines with numbers will be more eye-catching, and you’ll have better chances to be seen.

#4 Use Magnet Words

Knowing that email recipients have so many messages to read, you should ask yourself what motivates them to click. Earlier, we’ve concluded that numbers will increase click rates.

The question is what words should you be using? Again, it’s A/B testing that will discover trigger words for you.

You need to start with something. There are tons of suggestions all over the internet.

My recommendation are 48 ubiquitous power words from Linda Ruth and Curtis Circulation Company: Improve, Trust, Immediately, Discover, Profit, Learn, Know, Understand, Powerful, Best, Win, Hot, Special, More, Bonus, Exclusive, Extra, You, Free, Health, Guarantee, New, Proven, Safety, Money, Now, Today, Results, Protect, Help, Easy, Amazing, Latest, Extraordinary, How to, Worst, Ultimate, Hot, First, Big, Anniversary, Premiere, Basic, Complete, Save, Plus, Create.

#5 Consider Subject Line Length

Just like anything in email marketing, you can test subject lines all the time. Perform various tests like length, words,  or numbers.

One of the most common doubts is whether to use long or short subject lines. It seems reasonable to expect that short subject lines will perform better, since people quickly scan subject lines in their inbox, and too long lines will fail to grab attention.

Still, researchers like Return Path's claim otherwise.

Subject line length and average read rate

The Art and Science of Effective Subject Lines report:

Our research indicates that there is actually no correlation between the length of a subject line and its read rate. When comparing the number of characters in a subject line to the read rate, the Pearson's correlation value was - .03, which shows us that there's no relationship between the number of characters in a subject line and whether or not the email is opened.

So what should you do? Test, test, test. Don’t hesitate to use long subject lines, and eventually, you’ll find your optimal length.

#6 Use CoSchedule’s Headline Analyzer

Before the final decision about the subject line, I strongly suggest checking it with CoSchedule’s Headline Analyzer. Let’s imagine that you’re sending a 15% of discount to your subscribers, with the following subject line:

CoSchedule Analyzer

Click on Analyze Now, and you’ll get the results based on Common, Uncommon, Emotional and Power words.

CoSchedule Grade I got the B+ with a recommendation to improve the balance. I could do that by importing an uncommon word since I have none in the subject line.

However, this analyzer is primarily a headline checker, so I’ll scroll down the results to see if I can find something useful related to my subject line.

I can see how the subject line will look in an inbox.

Subject line in inbox

In this case, it’s important to have a 15% Discount visible. More than 60% of emails are opened on mobile devices. There is a risk that, in longer subject lines, important parts may not be seen.

After some more scrolling, I can see another important note.

Sentiment in subject lines

Positive sentiment is exactly what to achieve, so I’m pretty satisfied with my subject line.

#7 Email Subject Line Keyword Checker

OK, we’ve tested our subject line, but what about the keywords? For that purpose, we can use subject line checker Adestra.

Let’s use the subject line from previous example and see if there are better alternatives to keyword discount.

Choose a Sector Retail/Ecommerce, paste the keyword discount and click on Check my keyword.

Subject line checker discount

Both open and click rates are significantly below the average, so I could consider some synonyms like a price cut.

These results show that keyword price has much better rates. Unfortunately, this checker shows the result only for one word, not the phrase.

In other words, it’s possible that the term lower price would be even better than the price cut (here is the idea for the A/B test).

#8 Track Your Results

In every part of email marketing, you simply need to measure everything. Using tools like Jellymetrics you can track your click rates of your campaign.

But how will you know if your performance is good enough? For that matter let’s see some useful benchmarks.

According to emfluence, an overall average open rate is 22.17% and click rate is 3.74%.   A lot depends on the industry.

For example, the banking industry has the highest open rate - 30.06% because people are interested in newsletters from their banks.

Another intriguing fact is that 50% of Americans check their email while in bed. In other words, if you don’t have an interesting subject line, they will pass your email.


No matter how good content your email message contains, a bad subject line can easily crush your campaign.

That’s why writing good subject lines is an activity that deserves a lot of attention. If you take all the steps from this text, there is a great chance that you’ll improve the click rates.

In these steps, I didn’t mention arguably the most important activity - A/B testing. I didn’t do it because A/B testing covers up everything - numbers, words, and subject line length.