Subject Lines and Open Rates: Tips and Data-Driven Improvements

What are subject lines and open rates, and how do they relate to each other?

The subject line is basically an email’s headline, a short text that summarizes the email’s content. It appears in the recipient’s inbox and thus becomes the first thing that they see about an email. Here’s an example of some promotional subject lines i found in my inbox:

The open rate indicates the percentage of recipients who open a particular email. According to our research, the average open rate for emails stands between 20% and 30%, depending on the industry you’re in. 

The concepts of open rates and subject lines are quite closely related – since the subject line is the first thing your audience sees, naturally, it plays a big role in whether your email is opened at all. Although other factors matter as well, of course, like the sender name or the presence of email avatar. 

Top tips on writing great subject lines

So how do you write subject lines that people can’t resist clicking on? It’s all about standing out from the crowd, after all.

Shorten them

While there’s some debate among email marketers on the length of a perfect subject line, they all agree that brevity is key. Generally, the recommended length is around 40-60 characters, and for mobile, it’s even less — around 30 characters. 

So try to keep your subject lines snappy and short (ideally under 40 characters) to grab the attention of your readers straight away.

Compel, compel, compel

Prompt action by incorporating compelling calls to action (CTAs). Begin your subject lines with action-oriented verbs, such as “Get,” “Shop,” or “Download” to grab your reader’s attention and boost those open rates. 

You don’t want to overdo it, though, so steer clear of spammy tactics like writing in all caps or adding too many exclamation marks.

Spark curiosity

Humans are naturally curious. Asking interesting questions in your subject line will pique your reader’s attention. And remember, a little humor, clever wordplay, or fresh language can go a long way in making our emails stand out!

Induce a sense of urgency

Subject lines such as “Last chance” and “Ending tonight” are everywhere – and there’s a good reason for that. As basic as these subject lines are, they work by playing on the recipient’s fear of missing out, otherwise known as FOMO. 

As soon as there’s a hint of the time or the offer is limited, the recipient is pushed to open the email to avoid missing out. This sense of urgency is a great driver for conversions.

Deliver on your promises

Stay relevant and maintain integrity, this is important for building trust with your audience. Your subject lines must deliver on their promises, to make sure that your email content matches the audience’s expectations. Keep it genuine and consistent to earn your readers’ trust. Avoid over-promising!

Making data-driven improvements to subject lines

Once you’ve sent your campaign out, you may be wondering how to analyze and test the effectiveness of your subject lines.

Testing the performance of subject lines

Now that you have understood how to improve your open rates, it’s time to play around and test their effectiveness with some A/B testing. 

A/B testing, otherwise known as split testing, is a method used to compare two versions of something to determine which one performs better. Here’s how to do this:

1. Segmentation. Divide your email list into smaller segments to test different subject lines on distinct groups. Some of the most commonly used segments in email marketing include demographics, geography, behavior and purchase history, among others. In this case, however, we need our segments to be as representative as possible – if one group has only men and the other has both men and women, the samples aren’t fair. You should try to make sure the age and gender in your test groups match those in your full contact list.
2. Variations. Create two or more versions of your email with different subject lines. Make sure that only the subject lines are different, while the rest of the content remains the same. For example, let’s imagine that you want to prompt your audience to download your new app. Draft two versions of the same email, and use a subject line like “Download our app now to unlock exclusive features!” for one, and “Don’t miss out – get our app for free!” for the other. Alternatively, you could play around with emojis – assigning an emoji to one subject line and not the other.
3. Randomization. Randomly assign each segment of your email list to receive one of the variations. 
4. Measurement. Track key metrics (in our case, open rate). Analyze the data to determine which subject line performed best.
5. Iterate. Use the insights gained from the A/B test to refine future email campaigns. Use what you’ve learned to create subject lines that better connect with your audience.

While you can run an A/B test manually, using an email service provider (ESP) can streamline this process. For example, your ESP can segment your list of recipients for you, as well as track and analyze the results. 

If you’re using Selzy to create your email marketing campaigns, you can also use it to run A/B tests. This is what it looks like:

Now to a real-life example.

Tracking and analyzing the email performance

Here too, consider using an ESP that provides analytics and reporting features. Ensure that email tracking is enabled in your email campaigns, which most ESPs do automatically. 

You may view the open rates of your emails by accessing the analytics dashboard of your ESP. This feature usually provides detailed insights into open rates, click-through rates, and other important metrics.

This is what an A/B test looks like in Selzy:

You can also calculate the open rates by using the following formula:

The number of emails delivered excludes bounced emails and emails marked as spam filters.

Final thoughts

To wrap it up, subject lines are a pivotal point on your subscribers’ path to decide whether they want to open your email or not. Give them the attention they deserve, and set yourself and your campaign up for success.

• Email subject lines and open rates are closely related.
• You can make your open rates better by writing brief, unique subject lines, including CTAs, and making sure your subject line is relevant to the body of your email.
• Track open rates of your emails with the help of an email marketing service.
• Test the effectiveness of your subject lines through A/B testing, and iterate continuously.