., ? and ! – Does punctuation in the subject line help or hurt email performance?

How to best use punctuation in email marketing campaigns

Is the smartphone really killing off the period as a punctuation mark for texters? A recent story in the Washington Post says it is.

Where the full stop once marked the end of a sentence, the simple line break now claims that role in texting. The stop itself has evolved into a shorthand symbol that charges an otherwise innocuous sentence with deeper meaning, such as anger. It's less obvious than emoji and takes fewer taps on the keyboard.

That made us think (because we think about email all the time) about subject lines with stops at the end. Do they help or hurt opens, clicks and deliverability? And what about other punctuation marks? Do question marks really drive more traffic? And what’s the deal with exclamation marks?

To get some definitive answers, we turned to Touchstone's universe of virtual subscribers to see what impact punctuation marks had on their propensity to engage with subject lines containing punctuation marks. Because the Touchstone algorithm has the results of over 650,000 subject lines to learn from, we knew our virtual tests would produce real insights.

Here's what Touchstone’s virtual subscribers told us:

The full stop or period

The stop is an elusive mark. Marketers are split evenly into three camps: Some believe every subject line should end neatly with a stop; others believe that subject lines are best ended with no punctuation at all; and the rest can't be bothered to care about a silly stop.

The data suggests that stops do have a real effect on open and click rates. Moreover, the best results are achieved when stops are used sparingly. If you use stops sparingly in your subject lines (2% to 4% of your subject lines), then they take your subscribers by surprise ("Oh my god, a stop!"). Thus, they’re more likely to pay due attention. This translates to a boost of 10% to 20% in open rates.

Ending with a stop also has a positive effect on delivery rate, the increase in engagement results in a 0.5% increase in deliverability.

On the other hand, if you’re overzealous with the use of this punctuation mark, the data suggests you'll see a drop of 5% to 10% in open rates.

Bottom line:

2% to 4% of your subject lines should end with a single stop. Those subject lines will drive a 10% to 20% higher open rate. O.M.G.!

The question mark

The question mark is often oversold. "Generate mystery," the experts say. It makes the subscribers wonder about your email and makes them more likely to open.

The virtual subscribers disagree. Using question marks had dramatic negative effects on click rates across the board, despite having no noticeable effect on delivery rate or on open rate. Indeed, 72% of brands see a lower click rate – 8.1% lower on average – on their subject lines which end with a question mark compared to their other subject lines.

Although these types of subject lines are indeed good at generating attention, they perform poorly at triggering the right kind of opens: those from people with a real intent to buy your product. While these two effects cancel out when it comes to your open rate, your click and conversion rates will suffer, as will your revenue.

Of the three punctuation marks we studied, only the question mark generated sharply negative click results. It's not the question mark itself; rather, it's how you use it. You're probably asking questions that are too generic and failing to answer them in your email copy. You might get more opens than usual but fewer clicks.

The art of asking a question in the subject line is to have it be specifically about what the copy/products/offer is about. This way, the question subject line sets expectations and then meets them. High opens and low clicks usually mean you've set an expectation but failed to meet it in the email message.

Bottom line:

Most clients see an 8% drop in click rates on the subject lines that end with a question mark.

The exclamation mark

Can exclamation marks really convey excitement to the bored user checking his email? Probably not, but that’s not the point. Contrary to what many believe, the goal of the exclamation mark is not to have the subscriber jumping up and down upon reading about your sale. Rather, it should be used as a marker that a particular sale is special.

With it, you want to say, "There’s a great deal here, and the deal is so good we wanted to make sure you didn’t miss it by adding an exclamation mark."

And this actually works, too! When looking at brands that use the exclamation mark sparingly, we find that more than 70% of them indeed see a lift in their open rate when they use it, and that lift is usually about 10% to 20%.

Bottom line:

Exclamation marks work and should be used as part of a healthy subject line strategy. As long as you don’t overdo it, you could expect to find subject lines that end in exclamation marks have an open rate 1% to 20% higher than your average.

What you should do

Overall, it’s clear that the winning strategy here is one where you’re constantly mixing things up. Changing punctuation often is a great way to catch your subscribers’ attention and keep them interested in what you have to say. Even something as innocuous as adding a single stop at the end of your subject line is often enough, as the data demonstrates.

Remember that our results here are based on running tests against our entire virtual database. Your results might well vary, so it is important to test these findings against a replica of your own database too; something that is easy to do in Touchstone. If your population skews heavily toward or away from Millennials, for example, you might see different results from ours.

For more about using originality and variety in subject lines, check out this blog post and also get 15 tactics you can use to sharpen your subject-line skills.

Also, test your next subject line now, and get real-time predictions for opens, clicks and delivery rates as well as suggestions for better results.