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What do email marketers split test? (SURVEY!)

When it comes to subject lines for marketing emails, some work better than others.

For anyone who has worked in the field of email marketing for long enough to try a few different subject lines out, the above statement could not possibly be more obvious.

We can take it as a given that split testing email subject lines is something that all skilled email marketers are (or should be) doing on a regular basis.

But are they?

And are those who are split testing their subject lines doing so in an efficient and effective way?

These are important questions. Questions which need answering.

To get the answers, we here at Phrasee decided to conduct a survey and look deeper into email subject line split testing numbers.

We polled individuals across the global email marketing industry and received anonymous responses for 304 of those we reached out to.

The results were, to say the least, telling.

In particular, we wanted to know as common practice:

What do email marketers split test?



10% of respondents split test for this

While indispensable to all written communication, punctuation is probably the least sexy part of any message. This may be why so few of email marketers split test for punctuation in their subject lines. However, in many cases, punctuation can change the entire tone of a message and thus impact the success of a subject line a lot more than most would like to think.


Different product features:

25% of respondents split test for this

If an audience is interested in emails about a certain product or type of product, how much information should they be given in the subject line? Which particular features of the product being marketed will garner the most curiosity, and therefore the most clicks? Only 25% of email marketers split test for different product features to prominently display in their subject lines.


Price differentials (i.e. $50 vs. 50%):

Image credit: CBS


30% of respondents split test for this

Which sounds better? “Buy one, get one 50%” off, or “25% off”? They both mean exactly the same thing (except that in one case you have to buy 2). However, people will generally react to the two in completely different ways.  Isn’t it worth determining which works better for your audience? Seems like a no-brainer. Odd that only 30% of email marketers split test this…


Including the price/discount:

36% of respondents split test for this

Everybody loves a bargain, but does adding the exact numbers of the price or discount on offer actually translate into increased sales? Or is it enough just to say that you are having a sale, or that a special price is on offer? We think this is worth a look for any email marketing campaign. Yet only 36% of email marketers split test to find out how their audience responds.


Different adjectives:

43% of respondents split test for this

Adjectives are powerful words. They give marketers a chance to build and hone the perception of a brand, product or service in a way that no other part of language can. Incredibly, less than half of email marketers split test subject lines to determine what adjectives pique their audience’s interest.


Length of subject line:


58% of respondents split test for this

Does your audience respond better to brevity or detailed information? Are they more likely to click on a short, mysterious subject line or one that tells them exactly what they need to know, no matter how many words it takes? Does it make a difference to the bottom line? More than half of email marketers believe that it does, and split test their subject lines to find the right length.


Different call to action phrases:


77% of respondents split test for this

Unsurprisingly, the area for which the highest percentage of email marketers split test their subject lines is in call to action phrases. Presumably, the end goal of any email marketing campaign is to get the people on the mailing list to do something. 

Whether this be signing up for a newsletter, going to a store, donating money or visiting a website, an email marketing campaign can only be considered a success if the recipients feel compelled to carry out the action that the marketer intended. So, what call to action phrase is most likely to get the result the marketer wants? Like it can for all the other examples, split testing can help us find the answers.

So what does it all mean?

While split testing subject lines has become common practice for email marketers (about 75% do it on a regular basis) many may be testing for the wrong things, and missing the point entirely. Split testing has been statistically proven to work for those writing email subject lines. The gap lies in the methodology of the standard A/B split testing currently prevalent in the field.

For those wanting to increase the impact of email marketing campaigns through subject line optimisation, Phrasee is here, and we might just have the answers email marketers are looking for.

Check us out! 

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