5 Lessons We Learned From A/B testing 15 million emails in 2023

Sara Kappler
5 min readDec 11, 2023

As we close out the year, it’s a good time to reflect on the lessons learned and the insights gained through another year of effective email marketing. In 2023 alone, we’ve sent over 15 million emails for clients. That’s a lot of emails, and most importantly, it’s a lot of revenue generated for our clients.

Here are 5 lessons from our A/B tests that can help you have an even better performance next year in email.

1. Send Time Really Matters.

When it comes to email marketing, timing is everything. The moment you send your email can have a significant impact on its success. We’ve experimented with various send times and found that personalization is key. Platforms like Klaviyo offer Smart Send Time features that analyze recipient behavior and send emails at the most opportune moments. To make the most of this feature, test different send times, analyze the results, and draw conclusions based on your audience’s engagement patterns.

What we learned:

Each client is slightly different because each email list is unique, but one common thread we found is that the optimum send time test results pointed to a later time than we initially hypothesized.

For B2B: try lunchtime over morning.

For B2C: try late evening instead of early evening

For SMS, we’re limited by smart send time but try over lunchtime instead of morning.

2. Check Your Button Colors.

Sometimes, even minor changes in color can lead to substantial improvements in conversion rates. In our extensive testing, we’ve discovered that certain button colors consistently boost click-through rates. In particular, orange, red, pink, or yellow tones tend to perform exceptionally well. Don’t underestimate the power of color psychology in your email campaigns.

Why is this? We’re simple creatures and color changes can have our attention drawn to the call to action in an email. Also, with later sends, more users are in dark mode where more muted colors sometimes get drowned out.

3. Include Free Shipping/Return Policy Verbiage.

Trust and transparency are essential in relationship building, and email marketing is no exception. We’ve extensively tested the inclusion of shipping and return policy verbiage in our emails. Does including these value statements increase conversion? Including details about free shipping, hassle-free returns, and responsive customer service can instill confidence in your subscribers and drive conversions. Test different variations of this verbiage and monitor the impact on your click-through and conversion rates.

We found simple inclusion of these “trust statements” is enough to boost conversion. Meaning, you don’t have to dedicate a lot of retail to these, but it’s worth repeating and drilling into your audience if you have Free Shipping, LiveChat teams available, etc.

(These should also be apparent on your website: homepage, product pages, everywhere).

4. Use Enough Text.

While visually appealing emails are important, it’s equally crucial to strike the right balance between images and text. We’ve found that emails with around 50% text content tend to perform optimally from a deliverability perspective. This level of text provides sufficient context and information to engage your subscribers without overwhelming them with too much content. Experiment with text-to-image ratios to find the sweet spot that resonates with your audience.

Avoid the temptation to make your emails image only. It simply doesn’t increase conversion.

5. One Touchpoint is Better Than No Touchpoint.

Email design can be a rabbit hole of choices, from colors and padding to layout and fonts. What we’ve learned is that it’s easy to overthink emails. While optimization is crucial, don’t get caught in a never-ending cycle of refinement. Sending regular, slightly imperfect touchpoints is often more effective than infrequent, perfectly designed ones. Remember that consistency and engagement matter more than minor design tweaks. At some point, you need to take action and run with it, or you risk missing out on the rewards of timely communication.

About Centric Squared

At Centric Squared, we specialize in email marketing services, SMS marketing services, and List Growth services for small businesses. Our expertise and insights in A/B testing and email marketing strategies can help your business achieve exceptional results in your campaigns. Feel free to reach out to us to learn more about how we can assist you in reaching your email marketing goals.

In conclusion, the lessons we’ve learned from extensive A/B testing this year have been invaluable in fine-tuning our email marketing strategies. By paying attention to send times, button colors, verbiage, text-to-image ratios, and the importance of consistent touchpoints, we’ve optimized our client’s campaigns for maximum revenue. As you embark on your own email marketing journey, consider these lessons and consider incorporating a culture of A/B testing in your own email marketing strategy. You won’t be disappointed and your email revenue will thank you.

Ready for better performance for your email marketing? Let’s talk.



Sara Kappler

I run a CRM-Driven marketing agency. Mom of three. Flexible work advocate. Data nerd. Results-oriented.