It’s no secret—email marketing is one of the most effective marketing channels to engage customers and contribute to overall business growth. After all, email marketing boasts an ROI of 4400% (source), and 59% of marketers say it’s the most effective channel for revenue generation (source).

But, after a while most email marketers see their campaigns plateau. Not only do they struggle to improve campaign results, some even see campaign results worsen over time. Why is that? Unfortunately, there’s no one-size-fits all answer to this question. Maybe your subscribers are no longer interested in the subject matter. Maybe your email copy is getting too long. Maybe you aren’t even reaching your intended targets.

Until you thoroughly test your email campaigns, you will never have a definitive answer. If you’re ready to take your email marketing program to the next level, today’s blog post is for you.

Keep reading to learn the ins and outs of testing your email marketing campaigns!

Split Testing and Email Marketing

Before we get into specific variables, let’s quickly discuss the most common method for testing email marketing campaigns—split testing, or A/B testing. This method involves splitting your intended email list into two separate lists and sending a slightly different variation of an email to each.

We’ll use our first variable, your subject line, as an example. To perform this test, you would create two different subject lines for the same email. Then, you send “Subject Line 1” to a selection of your subscribers (Group A) and “Subject Line 2” to another group of subscribers (Group B). You’d then compare the open rates and clicks for both variations to determine which subject line is best.

Of course, you can test more than just an A and B variation if you want to test a third, fourth, or fifth subject line. Some variables will require more thorough split testing to discover which version your subscribers prefer.

Now let’s look at some specific variables you can test to improve your email marketing program:

1. Subject line

The subject line is the most commonly tested email marketing variable (source), and for good reason. It’s the first thing an email recipient sees—and it’s what they use to decide whether they’ll open an email, ignore it, delete it, or mark it as spam. In fact, 69% of email recipients will report an email as spam based on the subject line alone (source).

You should test several different elements of your subject lines, including:

  • Length: Compare subject lines with different word counts to determine which length is most effective. Seven words is the most common subject line length—but subject lines with just three words have the highest average engagement rates (source).


  • Word choice: Research shows that specific words in your subject lines can hurt your engagement rates—the worst performers include ‘whitepaper’, ‘forecast’, and ‘training’ (source). Try swapping out certain words for similar alternatives and test the impact on your engagement rates.


  • Clarity: Some emails have clear subject lines that tell you exactly what’s in the email, while others tease the recipient with vague, cliffhanger-style subject lines. Test these two different approaches to learn which style your audience responds to better.


2. Sender name

Do your campaigns perform better when your emails come from a real person rather than a company? Test different sender names—and then stick with the format that works best, so your subscribers don’t have trouble identifying your emails. Examples of ‘from’ name variations include: X Company, John Smith from X Company, or simply John Smith.


3. Call-to-action

The call-to-action (CTA) is a critical part of your email, as it tells the recipient what action you want them to take—sign up for a free trial, download a whitepaper, register for a webinar, etc. So, be sure to optimize your CTA to maximize conversion rates. For the best results, you should test the following elements of your CTA:

  • Location: Where does the CTA appear in the email? Do emails perform better when the CTA is at the top of the message, at the bottom, or somewhere in the middle?


  • Language: Test your CTA copy to determine which style and phrases convert best. For example—”Get your free eBook!” “Download your free eBook today!”


  • Appearance: Adjust the look and feel of your CTA, including color, font, and surrounding images.


4. Personalization

Personalization is one of today’s fastest-growing trends—not just in email marketing, but across all marketing channels. And, over half of today’s email marketers say that improving email personalization is their most important goal (source).

You can test email personalization simply by including or removing a subscriber’s name from your email or subject line. Or, you can get more in-depth by introducing dynamic content—content that changes based on a subscriber’s online activity—to a select segment of your audience. Test a variety of personalized elements to determine which ones help (or hurt) your engagement rates.

Personalizing your welcome emails helps create an outstanding first impression. It’s the key to building a fruitful relationship from the get-go. Build upon it by personalizing your transactional emails, product suggestions, and any other communication you send to your clients.

5. Day and time

You can’t control when a subscriber opens your emails. But, you can optimize your schedule to send emails on the days and times that they’re most likely to be read. Perhaps you’ve seen conflicting information on this subject. The truth is—you must test your own email cadence to determine what your own audience responds best to.

For example, let’s say you’re sending an email advertising a free trial of your new product. You send it to some subscribers on Monday morning and to others during the day on Wednesday. Conversion rates are much lower on Monday morning—leading you to believe your users are less likely to click through an offer at the beginning of their work week.

6. Frequency

In addition to testing when you send your emails, you should also consider how often you send them. Perform split testing on your email frequency—examine your results when you send emails once a week, twice a week, once every two weeks, etc. Testing allows you to find the delicate balance between emailing your subscribers too much, and not emailing them often enough.

7. Design

Email design serves a purpose beyond visual appeal—it can make a big impact on how your subscribers engage with your messages. Email design should be visually captivating without distracting from the most important parts of your email, namely the CTA.

Test your email designs by crafting different variations of the same message. Here’s an example: Let’s say you’re starting an email campaign to promote an upcoming webinar. You create two different email designs: one is a very simple, plain text email, while the other includes more graphics, photos, and a variety of colors. You then distribute these emails to similar segments of your email list and track which design yields higher engagement rates and conversions.

8. Target audience

Sometimes the problem with your email campaigns isn’t the contents of the email, but the subscribers you’re sending the email to. List segmentation allows you to break up one subscriber list into more targeted segments—but even the most experienced marketers struggle to execute email segmentation successfully the first time.

Fortunately, there’s an easy fix: 42% of email marketers say testing target audience is a very effective way to improve email marketing results (source). Test your target audience by sending similar emails to two different segments of your list. Observe which segment engages more with the emails to develop a better understanding of how to target specific campaigns.

Let’s look at a quick example: You sell sales enablement software. Historically, you send to a generic sales list. But, after your email results plateau, you decide to test the same messaging with two specific lists segmented by job title. The first list is made up of Sales Operations Managers and the second is made up of Sales Directors. After segmenting this way, you see engagement is significantly higher with the sales ops audience. This insight informs your strategy moving forward.

Key Takeaways

The above list is by no means comprehensive—there are many more email marketing variables you can test to improve your email marketing strategy. But, these eight variables are a great place to start if you haven’t yet explored the world of email testing.

Here’s one last piece of advice—don’t test several variables at once. If you test a campaign’s subject line, frequency, and target audience all at once, you’ll struggle to understand how each individual variable impacted your results. Perform one test at a time, and soon you’ll develop the perfect system to continuously improve your email marketing strategy.


About the Author: Sam Holzman is a Content Marketing Specialist at ZoomInfo where he writes for their sales and marketing blog. ZoomInfo is a leading contact database that helps organizations accelerate growth and profitability. Sam regularly covers topics related to sales, marketing, and recruiting, and likes to write about sports and travel in his free time.