Email subject line statistics that show why your first impression matters — Stripo.email

Did you know you may lose over half of your opens by not optimizing email subject lines? That’s right. Around 47% of recipients open messages based on the impression that lines give. Despite the quality content inside, the email can go unread with no second chances, forcing sales teams to go the extra mile to get the attention.

So, how great is the subject line’s impact on the campaign performance besides opens? We are about to find out.

Top 10 email subject line statistics you need to know

With no prolonged introductions, I suggest that we review the key 10 email subject line statistics, so you know what we are dealing with.

1. Email subject lines 61-70 characters in length receive the most opens.
2. Email lines with only 2-4 words outperformed the most popular competitors with 6 words in length.
3. Subject lines that create a sense of urgency have a 22% higher chance of grabbing attention and getting opened.
4. The subject lines with more than 241 characters reached the lowest open rates of only 23.5%.
5. Subject lines with the word “affordable” reached the highest click-through rate of 11.17%.
6. Subject lines with personalization have a 26% higher chance of being opened than impersonalized ones.
7. A single mention of the recipient’s first name increased open rates from 15.7% to 18.3%.
8. Around 69% of email subscribers mark messages as spam based on subject lines.
9. Subject lines without emojis have a lower unsubscribe rate of 0.14% than those with emojis.
10. Email subject lines with the word “guaranteed” reached the highest bounce rate of 5.74%. 

While each number digs into a different approach and metric, the impact is undeniable: increased opens and click-through rates, as well as decreased opt-outs and spam reports. 

How subject lines impact key email metrics

Email subject lines are small but mighty, and we have checked exactly what they can do. Besides being a gateway to email, they form the initial perception of the brand. Whether your target audience associates you with purely selling, engaging content, or irresistible offers is up to what you include in your subject line.

So, how exactly does it influence the email campaign’s metrics?

Open rate

Open rates show how good your subject line is and whether it attracts attention as it should. Think of an open rate as a sign of the subscribers’ impression: if there’s an open, your subject line catches an eye, and if not, it is probably not optimized. 

While you may test the length or subject line’s structure, let’s review how wording changes the game, according to GetResponse:

• a mention of the word “invitation” reached the highest open rate of 56.76%;
• the word “month” received a 53.88% open rate;
• adding the word “wanted” got a 51.53% open rate;
• mentioning the word “now” received a 52.52% open rate.

What may seem random at first makes sense after carefully analyzing the words’ impact: some create a feeling of urgency, some mention timeframes, and some — wishes or invitations to try. They are tightly linked to emotions and thus, they encourage email opens.

Click-through rate

Unlike open rates that define performance, click-through rates mirror how well your subject line is aligned with content. Why? The role of the subject line is not just to attract attention, but also to provide the reader with a glimpse of what’s inside. This sets their expectations straight before even opening the message.

Let’s review the tips that can help your subject lines:

• align with the main idea: What is the key message of your email? Your subject line should reflect the answer to this question;
• avoid false promises: While adding a catchy promise can be tempting, misleading the reader will likely make them unsubscribe or mark your email as spam;
• use action language: A good subject line should encourage an action, so add verbs such as “discover,” “try,” or “explore”.

(Source: Email from Dropbox)

Unsubscribe rate

Just as a compelling subject line increases opens, a low-quality one can raise unsubscribe rates. A single mention of the words “big,” “discount,” or “lifetime” can increase unsubscribe rates to 0.14%, 0.18%, and 0.17%, respectively.

Let’s compare two subject lines to explore this further:

Spam rate

Similar to the unsubscribe rates, spam rates reflect the quality of the line’s content. Email providers filter emails and mark suspicious ones as spam automatically.

So, what are the tips to keep your spam rates low? Here are common mistakes to avoid:

• spam phrases: Words such as “act now,” “exclusive offer,” or “only now” can trigger spam filters and move your messages out of recipients’ inboxes;
• exclamation marks: Using repetitive exclamation or question marks often overwhelms the reader and, once again, can trigger spam filters;
• capital letters: Besides creating a negative and pushy impression, using capital letters is a bad accessibility practice.

Psychology and language of high-performing subject lines

What is the first thing that comes to mind when you think of a catchy subject line? Is it the tone of voice, wording, or psychological tricks? This section explores how you can strengthen your subject lines to drive more email opens.

Let’s have a look at the key recommendations:

• curiosity gap: While the subject line must align with email content, leaving small gaps can add an element of intrigue and encourage opens;
• a sense of urgency: A good subject line motivates email recipients to act by creating a sense of limited time. You can add deadlines for discounts or sales to encourage engagement;
• social proof: Around 41% of potential customers believe that reviews are the element that impacts their purchasing decisions most. Consider adding a mention of positive feedback to your subject line to foster trust.

(Source: Gartner)

Subject line personalization impact

Only 17 out of 100 emails with non-personalized subject lines are opened. That’s how much influence personalization has. So, what are the most effective personalization elements?

(Source: Klenty)

I suggest that we take a look at Klenty’s findings in detail:

• first name: A mention of the contact’s name reached the highest open rate of 43.41% among other personalized subject lines;
• company name: Adding the company name reached a 35.65% open rate;
• pain points: Adding pain points to the subject lines got a 28% open rate.

This research highlights the main idea: personalization, whether standard or advanced, still grabs the recipient’s attention. However, it is not the only factor that impacts your campaign’s results, but that’s the topic for the next section.

The role of email subject line length

A perfect subject line strikes a balance between accuracy and brevity and delivers value in minimal length. Why? Besides the fact that lengthy subject lines feel overwhelming, they may be cut off by email providers’ limitations. On mobile devices, there’s even less space to fit in the idea, so the more precise you are, the better.

I suggest that we now define the top 4 variants of length and discuss why they work:

• email subject lines 61-70 characters in length receive the most opens of 43.38%;
• the length of 21-30 characters reached a 43% open rate;
• subject lines that are 31-40 characters in length received 41.99% open rates;
• email subject lines of 11-21 characters got a 41.98% open rate.

The key to the ideal length is to find a silver lining between using enough characters to reflect the idea, but keeping the subject line brief. 

Wrapping up

Despite often consisting of only 6 words, email subject lines are the first line of defense in the busy inbox. A good subject line is what separates the read email and the one that never gets to meet the recipient, so underestimating can cost a customer.

This guide has chosen the most recent statistics to show you why the first impression matters and how it influences your rates. I hope you have enjoyed the selection and create your next subject line with confidence. Good luck!