A/B Testing Email Best Practices That Go Beyond Subject Lines

It’s important to back your campaigns with data so you know which elements perform best. While everyone’s split tested for subject lines, there’s so many more variables you can test to make irresistible emails. There are three big results that you’ll ultimately seek to improve:

  • Open rate
  • CTR
  • Reply rate

Which you want to test for will help you choose the type of variables you should experiment with.

When A/B testing email campaigns, it’s important you test just one variable at a time; with multiple variables, you can’t easily determine which is working and which isn’t. Test often to ensure your lists remain optimized as you expand them and begin new campaigns.

So, what exactly should you be testing for anyway? Here are a handful of email A/B testing ideas that you should integrate into your campaign testing process right now.

Time of Sending

The day (and time of day) that you send out emails can have a big impact on email open rates. There’s no singular day or time that guarantees a high open rate, which means your campaign testing process should experiment with dates and times that work for your readers.

The First Impression

There are a handful of email A/B testing ideas for content. Most important, perhaps, is your email’s opening line. Appearing as a snipper under or after your email subject, this first impression makes a big impact on whether readers will open or not. The catch is that different email apps will show different amounts of characters and space per snippet. Experiment with different opening lines (in terms of language and length) and see which works best

Use of Visuals

Another element for A/B testing email campaigns is the use of visuals in your campaigns. Are emails visual-heavy, or should you stick to just one big anchor image at the top of the message? Test things like:

  • Where you place images, and how many you use
  • Whether visual buttons/clickable images increase CTR
  • Whether HTML formatting or plain text increase response rate
  • Image styles – eg. photograph vs. illustration



It’s a good idea to experiment a little with personalisation. Levels of personalisation can make an impact on both open rate and reply rate. A/B testing email best practices include testing for personalisation in both your subject like as well as the body text. When readers receive a personalised email, they may be more likely to open and respond. Try these variables in your campaign testing process:

  • Addressing the recipient by name
  • Mentioning an interest (base this on their email segment)

Sender Address

Are you sending your email blasts from a generic company address, or are you using the name of a public individual of the brand? If the latter, are you using the full name for formality, or just the first name for familiarity? A/B testing email campaigns should include experimentation of different send addresses to determine which are most effective.

Types of Content

You probably use your emails to point readers towards other types of content—video, audio podcasts and more. These should give you some email A/B testing ideas: see which types of media your readers like best! Doing so is not only essential to content strategy, but can help to improve your email CTR as well, making this test important among A/B testing email best practices.

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Links and CTA’s

Should you keep links in-line, or are they more effective when given their own lines? What color or formatting draws reader attention? A/B testing email campaigns with these variables will help you construct irresistible links that readers can’t help but click. You might also experiment with length of link text and word order. For example, whether offers and benefits are most effective at the front or back of a statement:

  • “Get 50% off your next purchase by sharing our video.”
  • “Share our video now and get 50% off your next purchase.”

Also consider placement of links and CTA’s in the body text: top, middle or bottom.

Email Length

Finally, a good campaign testing process should experiment with different email lengths. This varies based on your readership and frequency of emails; a longer message might be fine for a monthly newsletter, for example. It’s also worth remembering that services like Gmail can cut off messages after a certain length. Send one group of your list an email that matches your typical length, then try to truncate it into a more digestible version to your test group.