CATEGORY: How powerful is your subject line?

How powerful is your subject line?

How powerful is your subject line?

Before we get started, lets take a moment to put your email in context:

  • An estimated 306.4 billion emails were sent and received per day in 2020. Email statistics predict that by 2025, this number will reach 376.4 billion. (Statista, 2021)

  • Total send volume for emails increased by 7% in 2020. The highest increase was seen during March and July when there were an extra 1.5 billion emails sent each month compared to the same months in 2019.

  • An average person sends and receives 121 business emails per day.

  •  On average, professionals check their email 15 times per day, or every 37 minutes.

  • You have approximately 2 seconds to make an impact in the inbox, to motivate your recipient to open your email.

Your ‘vitally important email’ is lost in a sea of other emails that are also ‘vitally important’ to the people that sent them – so it is not surprising how many articles there are (including this one) with advice on how to make your email stand out in the inbox.

Who and what

Who and what are the only two elements that you have at your disposal to work with to engage your recipient in their inbox. We talk about “from names” in more detail in our dedicated article which includes detail about personalising, dynamic sender details and other tips to help make the “who” as impactful as possible.

However, today we are talking about the “what” and by this, I mean the Subject line and the preview text.

The single biggest thing that impacts email performance   

The subject line is arguably the most important aspect of an email marketing campaign. You have approximately two seconds to make an impact in the inbox, to motivate your recipient to open your email. 


An email campaign is a journey. If your subject line and preview text do not hook your audience enough to open your email; Your email design, content and any links will not be seen by the recipient. 

The key is to think of your subject line as your headline and your preview text as the sub headline. 

Newspaper publishers, particularly the red-tops, are the experts in capturing attention with a powerful headline.  

If you imagine your subject line is the main headline on the front page of your local tabloid newspaper; it can help you visualise how effective it is. 

sample newspaper with long headline


N.B. We are not talking about ‘click-bait’ here... well we kind of are... but the difference is that our subject lines are not aiming to be deceptive, sensationalised, or misleading. A good subject line could be viewed more as a "teaser" aiming to exploit the "curiosity gap", providing just enough information to make readers curious, but not enough to satisfy their curiosity without clicking through to the linked content. 


Is your subject line unique or remarkable?  

Back in the early 00’s Seth Godin introduced the concept of the “purple cow” in marketing. In summary, a purple cow is something that stands out, something remarkable. In a sea of black and white cows how do you make your cow stand out?  

As we saw above, whilst you a not in a general sense competing with consumer brands, high-street names or even B2B businesses – in the inbox of your email recipient you are. Your ‘very important’ email is amidst a sea of communications from every business, brand and individual that wants the attention of your audience.  

And you only have two seconds to make an impression. 

If I ask you a question – do you feel compelled to reply? 

Unique and remarkable is always the utopia to aim for, but this is difficult to consistently achieve. Other ways to achieve cut through with a subject line, like the title of this section, is to ask a question. If you ask a question of your recipient, then the question activates a different part of their brain and there is an additional psychological motivation to engage with you. 


It’s not all about you 

Think of each email as a process, in which catching your recipients' attention is the first step. The subject line is about THEM not you. What do they want to know, not what do you want to tell them. How, in just a few words, can you demonstrate that your email is relevant to them? 

Personalisation is a great way to highlight the relevance of your message, whether you reference their location, account, or name - they can see that this email deserves more than a two second glance. 


Ditch the housekeeping. Think about the value of each word in getting readers to open and click on your email. Many subject lines contain text which is more housekeeping for the sender than compelling for the reader. Common examples of housekeeping subject lines include:  

  • July Newsletter  

  • Latest news on [subject]  

  • Update from [brand] 

newspaper image with Essex Library update on the front page

Get the length right 

You’ll need to do some testing to determine the optimal length for your customer base, but we recommend no more than 9 words and 60 characters. 

A few more words or a few less won’t adversely affect your results too much, but too many words (over 20) or no words at all will cause a problem.  

50 characters (or fewer) is the general rule of thumb for subject line length. 

table showing length limits by device of subject lines


See more in 10 Questions every email marketer has asked at least once. And don’t forget about the additional characters in the preview text. 


Power of the preview 

If your email’s subject line acts as the title of your email, then the preview text is like the subtitle. It is that small bit of text after the subject line that displays in your email subscriber’s inbox before they click into the email. 

Preview text is usually the first couple of lines of the email itself, but this can be overruled to show specific text to support the subject line. Instead of wasting this space, use it to support the subject line and encourage readers to open the email by adding extra value. 

One mistake that we often see is preview text not being fully utilised. We see repetition of the subject line or even re-statement of who the email is from – but this does not provide any additional information on why this particular email, is worthy of attention. 

Preview text gives you extra space to embellish on your subject line, tease the email content, and capture your subscriber’s attention — make sure you make the most of it! 

Good email subject lines are fine on their own, but great email subject lines have preview text that plays along with them. Read more in our dedicated article. 


Test, test, and test again 

Test your subject lines. You can test word length, questions, humorous tone versus something more to the point, word choice, use or not of emoji or any other number of factors. 

Build up a picture of what your audience responds to and use your on-going learnings to optimise your campaigns. 

When optimising your subject line, use split testing to get statistically valid data. Other variables such as audience and time of sending can have a big effect on results, so just pit two subject lines against each other like for like. 

 If you are testing, don’t change too many things in one go or you won’t know what made the difference. 

preview of subject line cheatsheet

We have created a handy cheat sheet which you can download here

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