Increasing Newsletter Open Rate by Choosing the Right Email Subject

Increasing Newsletter Open Rate by Choosing the Right Email Subject

Jul 6, 2017
Increasing Newsletter Open Rate by Choosing the Right Email Subject

It is a never-ending marketing game. You have a newsletter and plenty of subscribers (congratulations by the way!). Your newsletter offers an advantage to your subscribers via useful information, insider tips, currently discounted products, and so much more.

And right now, you have created another newsletter email that is ready to be sent. You have spent a considerable amount of time creating its content, and all you need to do is to come up with an email subject and send it. That’s all. Easy, right? Well, not really.

The email subject plays a huge role in every sent email. It is the very first thing (and in many cases, the only thing) that your subscribers will see in their inbox and influences whether they open the email or not. This is even more important for newsletters.

These days, newsletters are everywhere. You sign up for a discount card, and you can bet that you will be included in some kind of a regular newsletter. You order some product from an e-shop, and it is very likely that you will receive yet another newsletter. In other words, it can get overwhelming really quickly.

So how do you fight back as a subscriber? You either unsubscribe from the newsletter, delete the email, mark it as spam, ignore it, or read it (great!). All this depends on your interest in each of the newsletters, but unless you unsubscribe or mark them as spam, you will glance at the email subject and, within milliseconds, make a decision whether you delete it or read it.

This leads us back to the email subject and its incredible importance. Every single time, you have only one shot, no more. Subscribers either like it and read it or hate it and skip it.

It takes practice to create eye-catching email subjects, but even then, you can never be quite sure that you hit the spot. For example, your subscriber base can be quite varied and contain different groups of subscribers, so thinking from all their viewpoints could be time-consuming and relatively hard. And after all, it could still be a complete miss (or hit!).

So, if you don’t want to waste your precious time that you invested into the newsletter content creation, an appealing email subject is a must!

And this is the exact moment when the Kentico email A/B testing functionality comes in handy!

In my case, I have an email ready to send. This is what I can see in the Email Marketing application on the Content tab of my newsletter:

It is a monthly newsletter, and I am not sure which of the following email subjects would be better:

  • Monthly news – We launched our premium service!
  • We launched our premium service last month!
  • 30 days later and our premium service is finally launched!

I can only assume which one would be the best and, as I want to ensure the best possible open rate, I am going to create an email A/B test by clicking the Create A/B test button and adding two more email variants:


Both of them will use the same content as the original email, but each of them will have a different email subject:

Now it is time to decide on the size of the test group. It is something that cannot be determined easily every single time. It hugely depends on the size and characteristics of the subscriber base.

For example, if every A/B tested email variant is radically different from the other variants, then I may need to test it only on a smaller percentage of my subscribers to find out the best performing one and then send it to the rest of them. Otherwise, I may mess up my subscriber base too much, resulting in a higher than average unsubscription rate.

Another thing to consider is the size of the subscriber group. It should be reasonably large, otherwise, the A/B test may not tell me anything significant at all. If I have at least a few thousand subscribers, I might consider A/B testing the emails.

On the other hand, even if my subscriber base is relatively small and I am not sure about the email subject, I may use the A/B test functionality to send different variants to all my subscribers anyway and then evaluate the results later for future newsletter mailouts. In other words, I would set the size of the test group to 100%, and Kentico would randomly send both variants to subscribers. For example, if I had two email variants (original + variant), then 50% of my subscribers would be randomly selected and receive the original email, and another 50% of them would receive the email variant.

As I have about 20,000 subscribers and am about to test the email subject to achieve better open rate, I am going to set my test group to 50%. Having three email variants (original + 2 variants), Kentico will send 9999 emails to the tested group, randomly choosing 3333 subscribers per each variant (3333 x 3).

I will let Kentico select the winning variant automatically based on unique opens two hours after the mailout. Whichever variant will receive more unique opens will be sent to the remaining 10,001 subscribers.

I have decided to send the A/B test at the end of a regular working day, so people will open it after they get back home from work. Within two hours, Kentico should have enough data to select the better performing email subject out of the three sent variants. It’s time to send it!


After two hours, I can see that the first variant has been doing much better than the other two, so Kentico chose it as the winner and sent it to the rest of the subscribers.

Awesome, I just managed to improve the open rate of the newsletter using the email subject A/B test!

Feel free to visit our documentation for more details on email A/B testing:

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