5 Types of Emails You Should Be A/B Testing (and How)

HiResA/B testing is one of Klaviyo’s core features and enables marketers to refine their emails to perfection. The ability to test content, subject lines, and timing allows you to drill down and optimize each aspect of your emails. A/B tests are especially useful for flow emails, since you can allow the tests to run for longer periods of time to determine the winners. Even better, you can continuously run new tests against the winners until you settle on the perfect email. For all of your emails, you can experiment with timing (triggering emails sooner vs. later), content, and personalization in subject lines. Below, I’ll discuss email-specific tests you can run to optimize your emails.

1. Abandoned Cart Emails

In your abandoned cart emails, there are several subject line variations you can test:

  • Product name vs. no product name — for example, “You forgot your [X product name]” vs. “You forgot something in your cart”
  • Test a sense of urgency — for example, “Your items are waiting for you” vs. “Hurry, before they’re sold out!”
  • Test the language you use — for example, “Your items are sad to be left behind :(” vs. “It looks like you left something behind…”

For content, you can test sending a product-focused against a brand-focused abandoned cart email. In a product-focused abandoned cart email, the abandoned items are the central focus, whereas the copy and brand philosophy are the central focus of a brand-focused abandoned cart email.

There are a multitude of other content tests you could run once you settle on the foundational structure of your abandoned cart emails. Add a variation that includes product recommendations to see how this converts — while you don’t want to distract from the abandoned product, it may be helpful for customers to see other products they’re interested in if they’re not completely sold on the product they abandoned.

You can also test varying senses of urgency and, if you offer a discount in the final abandoned cart reminder, you can test different types of incentives. For instance, you offer 10% off the purchase, you could test offering free shipping instead.

2. Browse Abandonment Emails

The tests you run for your browse abandonment emails will be similar to those you run for your abandoned cart emails. One thing to note is that you should be more cautious with the use of personalization than you might be when writing an abandoned cart email, since browse abandonment emails are simply triggered by viewing a product as opposed to adding it to a cart.

When testing the content of your browse abandonment emails, you can experiment with the type of product recommendations you include in the email. For example, you can test trending, bestselling, or manually curated products to see which convert best. Then, you can test how recommendations from different collections perform.

3. Win-Back Emails

The main thing you will want to test in your win-back emails is the discount you offer. You can experiment with different percent discounts, a fixed discount, and other incentives, like free shipping or promotions like buy one get one free.

You can also test different senses of urgency with varying degrees of pressure. For example, you could test a 2-day period to redeem a coupon code against a week long period to see which converts best.

4. Welcome Emails

With welcome emails, you may want to test the customary “Welcome to [X Store Name]” against something that is more unique to your particular ecommerce store. If you sell bikes, for instance, you may want to test out something like “Get ready to ride smarter.”

If the main goal of your welcome series is to guide subscribers towards their first purchase, you can test offering incentives for subscribers to purchase, like coupon codes. If the main objective of your welcome series is onboarding or introducing new subscribers to your brand, you can test the content that you provide in your emails. For example, you can test including an ebook against a curated list of blog posts.

5. Post-Purchase Emails

Because post-purchase emails are such a broad category of emails, you can test many different types of content. The three main types of post-purchase emails are “thank you,” product recommendation, and product review emails. You can simultaneously test up to five variations, so try these three types of emails and see which converts best.

You may also want to experiment with the timing of your post-purchase emails. For a baseline, start by sending a post purchase email five days after a purchase was made. Then, you can test sending sooner too see the impact. To learn more about how to encourage customers to make another purchase in your post-purchase emails, check out this post.


When A/B testings your flow emails, we recommend letting the test run for at least two weeks before selecting the winner of the test. When choosing a winner, it’s important to keep the variable you are testing in mind; for example, if you’re testing subject lines, you should use open rates as the metric for success. If you’re testing content, you should use conversions or click rates as the metric for success. Once you have selected a winner, you can then introduce another variation and repeat the cycle. This way, you can constantly test, improve, and optimize your flow emails.

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