Advanced A/B Split Testing

Everlytic’s A/B Split Testing tool is a powerful way for you to try different email design and content strategies. The tool allows you to send two versions of the same email to two groups of contacts. Everlytic then tracks all the contact engagement statistics, and shows you which of the two emails elicited the best response from your subscribers.

Learn more about how to send A/B split tests with Everlytic.

In this guide we are going to take an in-depth look at a variety of A/B tests you can send.

Testing Process

We cover the process of A/B testing in our first guide, so we’re only going to brush over the steps here:

  1. Decide what you want to learn.
  2. Decide the rules for your test.
  3. Run the test.
  4. Analyse the results.

Email Subject

The email subject line is the first thing your subscribers will see when they receive your email. Your subject line will either entice your reader to open your email, or fail to interest them – leaving your carefully composed email on a short trip to the trash can.

Careful testing can help you tease out which kinds of subject lines your readers will respond to best.

35% of recipients open emails based on the subject line alone. 69% report email as spam based on the subject line.


With Everlytic, you can add personalisation tags to your email subject lines. Basic personalisation is very common now. While starting a subject line with “Hey Angela…” may seem unoriginal, there are many other personal touches you can use to grab your reader’s attention.

Why not try some of these:

  • First and last name: Just because it’s common, doesn’t mean it won’t improve your open rates.
  • Location: If you know where your customers are, you can tailor the subject line to them (weather, holidays, etc.)
  • Personal preferences: If you collect information about a contact’s personal preferences, you can include this when sending emails. For example, you can ask your subscribers to specify their favourite colour when they join your list, then, you can use that information when sending emails.
Personalised subject line in an email from Amazon.

Personalised subject line in an email from Amazon.

Subject Line Length

There is no hard and fast rule about how long email subject lines should be in order to entice the most opens. This makes email subject line length a great variable to test on your readers.

When testing subject line length, consider these factors:

  • The devices your clients use to read email on. Everlytic’s Email Platforms Report shows you which email platforms your readers are using to open your emails.
  • Past subject line performance. Browse through your email history and take note of which subject lines are associated with your best and worst performing emails.

Data from Return Path shows that 65 characters seems to be the ideal length for an email subject line. However, it is still worth your time to test your audience, and their preferences may be different.

Brand Name in Subject Line

If you want your readers to instantly recognise your brand in the email you’ve sent, consider putting the brand name right in the subject line. This will help your readers know what the subject of the email is before they open it. Unfortunately, it also means that if someone isn’t interested in reading about your brand when they receive your email, they may delete it without opening it.

Formal vs. Informal Tone

Changing the tone of your subject line from formal to informal (or vice versa) might make a difference in your reader’s interest in your email. The success of this depends largely on the type of readers you have. A more business-oriented list might fare better with formal emails, while a casual clothing brand might do better with informal language.

Fear vs. Joy

People respond very quickly when they experience an emotional reaction to something, even email. Fear is a very powerful motivational force, and if you can elicit the “fear of missing out” in your subscribers, you may see a good increase in open rates.

Alternatively, joy can also entice subscribers to read your email. Use your subject line to promise them happiness, and they might be more likely to read your email.


Your Call-to-Action (CTA) should be obvious - make it stand out from the rest of your content so that readers can immediately see it. Make sure it looks like a button. If it’s obviously clickable, people are more likely to click it. Beyond that, experiment with exactly where you place the CTA, and test whether one is better than multiple buttons.

Deadlines to Increase Urgency

Playing on everybody’s inherent fear of missing out again, test deadlines in conjunction with your CTA to see your readers react to being given a ticking clock.


You can experiment with various CTA placements in your email to see which one works better. You may find your audience responds better to the CTA in the middle of the body, rather than at the end.


Experiment with different CTA designs. Change the colour, size, font, or shape to see which one gives you the best feedback. Just remember to only test one change at a time.


Try using a single CTA in one email, and more than one in other emails. You may find that your readers respond better when there is one CTA than when there are multiple buttons.

This email has a

Email from Help Scout with a single, centered CTA.

Email Body Text

A/B split testing allows you opportunities to try different content strategies. Here are a few suggestions which you might like to experiment with.

Special Offers

A/B tests are a good opportunity for you to try out different special offers to see which ones your audience responds to best. Discounts, giveaways, and coupon codes are a few email-based special offers you can try.

Different Tone

Try writing your emails in different tones. Do your readers respond more to emotional language, or text which is more research-based?

Emotional language might lean more towards evoking emotions (similar to the fear vs. joy email subject), which are a powerful motivator. However, you may find that statistics and evidence are more intriguing to your audience.

Excerpts or Full Text

Should you provide short excerpts of content in your emails (e.g. if you are sending blog content or curated emails), or would it be better to send the full text?

Full emails are more immediate, your readers don’t need to visit a separate web page to view the whole article. However, if you want to drive more readers to your web site or gauge interest in your content, you might want to provide shorter snippets of text with a link to the full text elsewhere.

Excerpts are useful for building your click-through rate, while full text emails are better for building your relationship with your readers.

Visual Properties

Graphics, such as photos, animations, or gifs, can make your email much more attractive and appealing. However, they also greatly increase the size of your email. They also pose a spam risk: if you use too many images, your email may be marked as spam by the receiving server (as spam emails often consist of nothing more than one big image).

When testing graphics in your emails, consider experimenting with the following image properties to see what resonates best with your audience:

  • Larger vs. smaller graphics
  • Photographs vs. animations
  • Text-to-image ratio


Colour is a highly effective way to draw attention to your email, and to elicit responses from your readers. You can experiment with the background colour, the colour of buttons, and the colour of headings and other accents in the email.

We recommend changing only one colour per test (e.g. one email with a red background, the other with a green background), so that response to variations is easier to track.



Email Layout

Finally, experiment with the layout of your emails. Image placement, number of columns, and the position of buttons and links can all have an impact on how well your readers respond to your email. Just remember to only test one element at a time.

Now that you've got a ton of testing ideas, get to it. Happy testing!

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