How to Split Test Marketing Emails

How To Split Test Marketing Emails

You should always be improving the marketing emails you’re sending to your readers.

If you’re sending email campaigns, checking your reports, and making changes are you hoping that your results will improve?

Are you measuring changes or are you guessing?

So how do you measure the impact of a change?

Enter split testing.

You probably want to know how to split test marketing emails.

What is split testing?

Split testing, also known as A/B testing, is a technique used to send two different emails to readers. What we’re doing is comparing which of the two emails performs better based on the results we see from each group.

To be a truly effective technique, there should be only one difference between the two. For example, two emails sent with the only difference being the subject line.

How to split test

How depends on the email service you’re using. There are as many ways to split test as there are email service platforms. Too many to cover here.

The good news is that most emails service providers will have the ability to split test almost any aspect of your emails.

What to split test

Subject lines

The subject line is one of the most important elements of your marketing emails. It’s one of two things that people use to decide whether to open your email or not. The other is who the email is from.

If you only test one thing, you should be split testing your subject lines.

There are different aspects of a subject line that can be tested.

Here are a few.


There is no consensus on the ideal length of a subject line. Some say 40 characters, others say 80.

But your subscribers are yours. They’ll ‘like’ aspects of your email subject line that other audiences don’t.

Maybe most of your audience are reading emails on smartphones. They’ll see fewer characters than someone reading emails on a desktop.

Try testing emails with subject lines of different lengths.

Word order

Did you know that your audience, the word order can make a difference to open rates?

Here are two examples:

Get 15% off your next purchase using this discount code

Use this discount code to get 15% off your next purchase

In the first version, the benefit is at the beginning of the subject line. English speakers will read from left to right and so see the benefit first. This could increase the open rates.

Next time you’re writing the subject line for your email campaign, consider testing the order of the words to see if front-loading the benefit can help improve your open rates.


If you’re sending a newsletter with multiple pieces of content, then one test you can run are subject line variations based on different pieces of that content.

Testing in this way gives you an insight into the type of content that your audience want to hear about the most.

Next time you’re writing a subject line for your email newsletter, consider testing different pieces of content in the subject line to increase the number of opens your campaign receives.


People love to hear and see their name. It’s in our nature.

Including the recipient’s first name in the subject line has the most impact in increasing open rates.

Two subject line tests you could run are:

• Including a recipient’s first name.

• Don’t include a first name.

Remember, your audience is different so don’t guess, test.


A picture is worth a thousand words. Why? Because research shows that the human brain processes images 60,000 times faster than text. This means that if you want to explain an idea quickly, consider using an image.

There are a number of ways images can be split tested.

Images vs no images

Images could be distracting to some audiences. Test if this is the case with your audience.


There are many different types of visuals you can include in your marketing emails.

Photos vs clipart? Colour vs black and white? Static vs gifs?

Which works best? It completely depends on your brand, audience, and layout of your campaign.

So, next time you are creating an announcement campaign, consider A/B testing the style of images you include to see which works best for your business.


According to research by Microsoft, smartphones have left humans with such a short attention span that even a goldfish can hold a thought for longer periods of time.

According to the study, the average human attention span has fallen from 12 seconds in 2000—around the time the mobile revolution began—to eight seconds today.

A goldfish is estimated to have a 9-second attention span.

This reduction in attention span has significantly increased the importance of great writing in your emails. If you can’t quickly and easily explain your product or offer, you’ll struggle to get your subscribers to click-through on your campaigns.

You can discover what great copy looks like for your audience by A/B testing different copy in your email campaigns.

There are a number of features in your copy that you can test, so we’ve compiled a few ideas to help get you started:


With the mobile revolution driving a decrease in attention spans, there’s a trend in email design towards using shorter copy.

This email from La Mer is a good example. It features minimal copy and, instead, allows the beautiful edge-to-edge imagery to really deliver the message.

Would this work for your brand? Or are you better off including longer-form copy that explains in detail the benefits and features of your product?

The answer is largely going to depend on the design of your email, your audience, and the complexity of the product you are selling. Next time you are creating a new product announcement campaign, consider testing whether short or long-form copy gets more of your subscribers to click-through and make a purchase.


According to studies, including personalisation in your email campaigns can increase click-through rates by over 14%.

The team at Dropbox realises this and leverages it to their advantage, including the subscriber’s company name in the email to make the invite more relevant to the subscriber and increase the chance they’ll attend the event.

Dropbox – A/B Test – Personalise Content with Company Name

If you have extra details on your subscribers stored in your email list (such as their company name, location, or other attributes), consider test personalising the body copy of your next campaign to see if the increased relevance drives increased results.


The tone you use in the body copy of your email campaigns can have a big effect on the number of click-throughs you receive.

Studies show that, when you incorporate positivity into your copy, you engage your reader’s brain in a much more powerful way, enabling them to easily understand your key messages and increasing their motivation to click-through and purchase your product.

Next time you are writing copy for your email marketing campaigns, give some thought to the tone in which you are writing and consider testing whether a positive tone could outperform a negative tone, in terms of driving click-throughs and purchases.

Calls to action

Your calls to action are one of the most important parts of your email marketing campaigns.

They help increase your email click-through rate by making it clear to readers exactly what the next step is.

Given the importance of calls to actions in driving click-throughs, it’s a good idea to A/B test them to make sure you’re getting the best results.

Here are a few ideas as to what you can test:

Button vs. text vs. image

There are three options for creating calls to action in your marketing emails: adding buttons, including a simple hypertext link, or adding a linked image.

Campaign Monitor split tested using buttons vs text. They found that using buttons performed better with a 27% increase in click-throughs over text links.

Button vs link A/B test example

Image Source: Campaign Monitor

However, this may not be the result you get. Other marekting emails perform better with simple text based links.

You will only know after split testing your campaigns.

Button copy

Button vs. text vs. image is just one test you can run on your call-to-action. The words you use can have an influence as well.

For example, using action oriented words such as “Get your ebook” might perform better than “Download”.

Again, different groups of readers respond in different ways. What works for some, may not work for you.

3 tips for running more effective split tests

Email service providers such as Campaign Monitor make it quick and easy to run split tests on your emails without having to create multiple versions. With others, such as ActiveCampaign, you need to create two versions and then test the results of each.

Regardless of the platform you use, here are some tips to help you successfully split test your emails.

1. Have a hypothesis

If your goal is to get a positive result from your split testing, it’s recommended you have a basic theory as to which of the two versions will perform better.

Here are some examples of what a basic theory might look like.

I expect that the version with the recipient’s first name to the subject line will have a higher open rate compared to the email that doesn’t.

I expect that the version that uses a button for the call to action will have a higher client-through rate than the version that uses a text linked call to action.

You don’t need to write these down. Just have a basic idea as to which email version will perform better.

2. Prioritise your split testing

Given all the suggestions of areas that can be split tested, you may find you want to test everything. And that’s not a bad idea. But you need to decide what’s more important to test.

For best results, decide which elements are more important than others.

How do you do this?

One way is to use the ICE scoring method.

Developed by Sean Ellis, the ICE score is a method you can use to determine project priorities.

The ICE is an acronym for Impact, Confidence, and Ease.

Impact: How big an impact do you think this change might have? For instance, if you wanted to test including a recipient’s first name in the subject line, will this change have a bigger or lesser impact than using a button as a call-to-action?

Confidence: How confident are you that this change will have a positive impact? For example, how confident are you that including a recipient’s first name in the subject line will give a better result than using a button as a call to action?

Ease: How easy is it to implement this split test? For example, adding a recipient’s first name to the subject line will take would take less than 30 seconds. Adding a button as a call to action along with a link, colours, text will take longer.

Assessing each of split tests you want to try, against these three elements will help you set a priority. The true spirit of the ICE method involves some basic maths. I’m not going into that here. You can do your own research.

3. Build on your results

Not every split test will give you a better way of doing things. Sometimes, split testing will show you that a particular change gives you a negative result.

Regardless of the result, you should be learning something about how you’re doing things. The aim is to create the best email marketing emails for your audience.

Wrap up

Stop guessing and start testing. Split testing is the most effective way to increase the impact of your emails.

Prioritise the elements you’ll be split testing.

Have a theory about how the change will improve your email.
Setup your split test.


If you see a change, whether it’s what you expect or not, you’ve still learned something about your readers. Either way, your marketing emails will improve over time.

Inbox Insights: Weekly email marketing tips, blog post and course updates delivered to your inbox. Sign me up.
Like this article?
Share it
Drop files here or
Max. file size: 50 MB, Max. files: 3.