We're thrilled to announce the acquisition of Social Method, a premiere performance-based media and creative agency.

Learn More
Blog Post

Best Practices for Email Marketing Split Testing

June 23, 2017
Table of Contents

Are you struggling with your email sequence conversion rates? This is a tell-tale sign that you should start split testing your emails. Email sequences are an essential part of the overall marketing strategy, and as with any marketing initiative, it is important to be constantly testing and improving.

Testing your email sequences is crucial to understanding which emails are performing and which are not. By testing various elements in those emails, you are steadily improving your chances of acquiring new customers and bringing old customers back into the sales funnel.

Testing may seem like a daunting task, but fear not, there are simple elements you can start off by testing that will help you fix the problems in your current email funnels. We have outlined the best practices of split testing to get you started.

What Is Split Testing?

Split testing, also referred to as A/B testing, is a type of test that involves testing only one variable. The most important thing to note when you are split testing is to make sure you are only testing ONE element instead of testing multiple. By testing only one factor, you can definitively tell which exact component potential customers are drawn to in each email.

Related: Why the One Key Email Metric You’re Ignoring Is Derailing Your Campaigns

For example, if you are testing the subject line in an email, you would test: “10 Ways To Stay Healthy This Summer” vs. “How to Stay Healthy in the Heat” and that would be the only differentiating variable in each email. That way you are able to figure out which subject line is converting more people to open the email.

Elements To Test

So now that we understand what split testing is, where do we start? The first step is to figure out which element you are going to test first. When in doubt, the subject line is an excellent place to start. Below are seven elements to test and tips for testing each.

Subject Lines

We touched on this briefly above, but the idea around subject line testing is to see which subject line is resonating with consumers more. The subject line is the first piece of content that your customers will read and therefore is one of the most important, if not the most important component of each email. If you have a stale subject header that is not converting, the rest of the content in the body of the email doesn’t matter because no one will be reading it.

Some basic testing tips for subject lines are:

  • Asking a question vs. Making a statement
  • Using a numbered list (10 Ways, 5 Tips, etc…) vs. non-numbered list
  • Test buzzwords words such as shop, get, download, save
  • Test the word “free” in your subject line
  • Test a shorter subject line vs. a longer one

*Above shows an example of testing a non-numbered list vs. a numbered list subject line

In addition, we have found that brackets perform quite well in subject lines and in our experience has drawn readers’ attention. Once you determine which subject line is converting best, you can deactivate the underperforming subject line entirely and start testing another subject line against the winning subject line or move on to test another element. As with any testing, there are many different strategies that can be used, but these basic methods are a good place to start.

Length of Copy

The length of the copy in your email is an important factor to consider. In general, emails are kept relatively concise. In some cases though, long form content can work quite well. For example, if this is the first ever email they are receiving from your company or you are trying to overcome multiple objections with your email copy.

When you are testing the length of copy, start with testing long text blocks vs. short text blocks. A tip when starting your testing is to take out five sentences and get to the point of your email more quickly. Test those variations (one with five sentences taken out and the one with the complete copy) and see which one is converting potential customers more successfully. After looking at the data and determining which variation is performing better, you can move on to test the tone of voice.

Angle of Copy

The angle of copy is what the tone of your email conveys. Is your email focusing on the benefits consumers will receive or on the things they are going to miss out on? Everyone is different when it comes to what will motivate them to take the next step in the buyer’s journey. For example, certain people are more likely to opt in if they feel like they will be missing out on something if they don’t. On the other hand, that tactic won’t work for everyone, and instead, some people are inspired to take the next step once they learn about the benefits they will receive from your product or service.

Create one variation of your email that has a positive tone of voice and explains the benefits and all of the great things that will happen if consumers opt in. After you have created this version, write another variation of the email that focuses on the “fear factor” and include content that centers around what they will miss out on if they do not opt in.


This testing element is quite simple. In one email, include an image and in the other variation only include text. Test these two emails to see which one performs the best. If the email with the image wins, you can try testing two images in your email vs. only one image. The image you choose is also important to test. Testing a stock photo vs. a photo that looks more natural or even testing a horizontal vs. vertical photo. Or you can try testing a static photo versus a gif.

*The email on the left doesn’t include an image, whereas the email on the right includes a screenshot of the blog post that we are trying to motivate people to read.

Day/Time of Sending

This can be a tricky element to test as everyone has different email habits. For example, some people clear out their inboxes in the morning, so a great time to try sending your emails are later on in the morning. But, this email habit isn’t true to everyone. It is important to figure out what time of day is best for your buyers and therefore when they will engage the most. To start off, you can test early morning vs. mid-day or mid day vs evening. Through this testing, you are able to understand when your market is most likely to engage and take the next step in the buyer’s journey.

RelatedThe Perfect Duo: PPC and Email Marketing

Another component that is important to test is the day that you send your emails. Are your potential customers more likely to engage with your emails on Monday’s or Wednesday’s? Or are you getting a higher rate of conversion on your weekend emails? By testing different days, you can start to see a pattern of when your potential customers are paying the most attention to your emails.

An additional factor to consider is whether or not you want to set an expectation for your consumers. Do you want your customers to expect to receive an email from your business every Tuesday at 8am or do you want to take them off-guard and choose a different day/time for every email? By testing the day/time of sending you can figure out if your market responds better when they are emailed at the same time each week or if they are engaging more when they are surprised by the email.


Call-to-action! A prerequisite for all emails. There are many aspects of this element you can test. For starters, you can test using CTA text vs. using a CTA button. Also, you can test the placement of the CTA in your email. Try placing your CTA at the beginning of the email vs. the end of the email or test the CTA in the middle of your email.

Testing a CTA button comes with its own set of testing elements. For example, you can test a designed button vs. just a hyperlink CTA. Or you can strictly test buttons and change the size or color to see which converts the best. Below you can see two examples of CTAs. The CTA on the left uses a button and the CTA on the right uses a hyperlink to engage consumers.

The text of your CTA matters and is important to test. You can try testing more personalized text, “My” vs. “Your” – “Get My Quote Today” vs. “Get Your Quote Today” to see which text resonates more with your customers. In addition, do the phrases sign up, register here or download my “x” perform better?

Other CTA testing tips include: putting the CTA in the form of a question and testing the frequency to which you place CTAs in your emails.


No one likes to get bombarded with emails, and this is critical to understand when you are implementing your company’s email campaign strategy. The frequency and quantity of emails you are sending is important to test. How many emails should you include? It depends on each email sequence; for instance, a welcome email sequence is usually three to five emails, but in some cases, it can be greater or fewer than that.

There can certainly be too many emails in your sequence, and additionally, there can be too few. That fourth email could have been the final push your potential customer needed. Or on the other hand that 6th email was one too many for your consumer and they decided enough was enough. It is recommended to start lower and build up. Once your initial emails are performing then you can continue to add more emails to your email marketing campaigns. Every email list responds differently. Your email list, for example, may welcome multiple emails in their inbox. If you don’t test it, you won’t know their preferences.

Email Testing Best Practices

Don’t jump to conclusions. What you might think will perform better, in reality, might not appeal to your consumers which is why testing is so important in the first place. For example, you might be surprised to learn that some emails with no images perform better than emails that include an image. Most people would assume that an email with an image would outperform an email without an image any day.

If you aren’t sure which element to start testing, start with the subject line. This is the first piece of content that customers will read and it has a direct affect on how many people will open the email. If your subject line isn’t grabbing the attention of your consumers and no one is opening the email; the rest of the content in the email doesn’t matter.

When you are testing, these emails must go out to at least 1,000 people in order to get conclusive data. Ideally, sending the two variations of emails out to over 1,000 people is preferred.

What data should you be looking at? Four important metrics to look at while split testing are:

  • The open rate
  • The click-through rate
  • The conversion rate once they are on your website
  • The unsubscribe rate

It is crucial to listen to the data and make changes to your email campaign based on the outcomes of your testing. This data is important and is showing you what your consumers prefer, so pay attention to this information!

Try not to get overwhelmed. Everyone has a different method to testing email sequences, but the information above is a great starting point. The most important thing to note is that it doesn’t matter where you start, as long as you start. The whole point of testing is to understand your consumers’ habits and preferences and motivate them to take the next step in the buyer’s journey.





Empowering you to break the mold.

Kind of like a full-service agency, kind of like an in-house CMO. Elevate your brand's presence with custom strategy, channel expertise, and flawless execution.

Learn More