Increase Your Email Open Rates with A/B Testing

Author: Steve Donehue
Posted: Jun 7, 2018

Topics: Web Development

A/B testing has been around for years. If you haven’t started implementing A/B testing, today is a great time to start. Most email marketing platforms now offer some sort of A/B testing as part of their service. You can A/B test almost anything on emails and websites, but some of the most popular elements to test are: subject lines, headlines, CTA buttons and imagery. For the purpose of this article, we are going to focus on testing email subject lines to increase open rates.


To set up the test, we want to first establish our goal to verify the winner. In this case, the winning subject line will have a significantly higher open rate than the other subject line. We also will need to make sure that we are setting up a fair test. That means that we are randomly separating our email database 50% to 50%. In addition, we must send our test at the exact same time. We can’t email the A version at 11 AM and the B version at 5 PM because this change may impact open rates, making our test pointless.

Another important component of A/B testing, is to make sure that you’re testing very unique options. You don’t want to test a subject line with the A version being “Read These Handy Marketing Tips” and the B version being “Check Out These Handy Marketing Tips.” Instead, you want to compare very different variations, like testing your typical email subject line with the headline of the first article. Other options would include personalization tokens or even emoticons, if appropriate for your audience.

If you seek scientific significance... Significance is determined by two factors: the first is the volume of your audience that you’re sending an A and B version to. The second is the conversion rate of the A and B versions. So, we’re looking for high volume and a big difference between the conversion rates. Typically, we’re looking to achieve a 95% significance rate. HubSpot created this handy-dandy calculator that walks your through ensuring significance.

Once you’ve run these experiments, you’ve got to determine “why” one subject line beat another headline. It is these findings that can influence future creative and strategy.

You have to plan to A/B test, it can’t be an afterthought. The best time to think about A/B testing is before you even start on creative. During the creative process, you may have two great subject lines, but really no reason to guess which will perform better. This would be an ideal time to plan for an A/B test.  Don't forget to check your email strategy against these must follow FTC rules. 

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