Put These Words In Your Subject Line to Boost Your Click Rate

on under E-Mail Funnels, Tactic Tuesday.

If there's only one thing you've ever learned from me, I hope it's this: test. Run quantitative, statistically significant tests on all of your assumptions as often as possible. Every one of us is wrong about something, and even when we're right, things change.

If there's only one other thing you ever learn from me, I'd hope it's this: scientifically backed advice is the best place to start. You can throw random tests at the wall and see what sticks, but the best tests start either with informed intuition, or the data of others.

And that's why I love studies like the one recently released by Adestra, which compiled a list of words used in over two billion emails within 90,000 campaigns, and found out which ones seemed to do best. So let's take a look at the results, and what they imply.

Selling Words

Ah yes, the art of selling, that area of marketing that SEOs and content marketers wish they could put off indefinitely. We all know that modern marketing is much more about customer retention, engagement, and brand lift than it is about selling things, but we also know we'd be insane if we didn't actually ask our audiences to buy something every once in a while.

Here are the most noteworthy (best or worst) words used for selling:

  • "Free Delivery" - This had the absolute best click rate of all the words studied, 135 percent above average. But it's not all sunshine and unicorns for this particular phrase, because it also had an 82 percent worse unsubscribe rate than average, the worst unsubscribe rate of any in this category.
  • "Sale" - This had the second best click rate for selling words, 60.7 percent above average, but it also had a 32 percent higher unsubscribe rate, the third worst unsubscribe rate.
  • "New" - This was the only sales-oriented word that had an above average click-through rate and a below average unsubscribe rate, making it a safe go-to. The numbers aren't all that impressive, though. The unsubscribe rate was only 2.6 percent below average, and the click rate was only 38 percent above average.
  • "Only" - This word really hits home just how outdated scarcity tactics have become in the digital era. This had the worst click rate, 37 percent below average. It's unsubscribe rate wasn't terrible, but it was still 12 percent worse than average.

Put simply, selling words almost always lead to unsubscriptions, so you're going to have to use them sparingly if you want to retain that audience.

Content Words

Okay, now for all that trust-building, inbound, retention, shareability-type stuff. The stuff we like. We must be pretty much guaranteed to see above average results with these, right? Well...no. It depends in large part on your choice of words, even when they aren't about selling. Take a look.

  • "Issue" - Readers think "issues" are a bit dated, apparently. While this did have a 10 percent above average click rate, the unsubscribe rate was a horrendous 30 percent higher than normal.
  • "Video" - This probably won't surprise you, but telling users you've got a video really perks their attention. The click rate was 65 percent higher than usual, the best in this category. Unsubscribe rates were also great, 26 percent below average, tied for third best in category.
  • "Alert" - At least for now, alerts seem to do great. They're almost tied with videos on click rate, 62 percent higher than average. Better still, they have the lowest unsubscription rate in category: 63 percent below average.
  • "Webinar" - Apparently, readers are suffering from a bit of content marketing overload, because they don't seem interested in these, at least when you use that particular language. This had the worst click through rate in the category: 70.7 percent below average. Webinars even led to unsubscriptions 8.8 percent above average.

While unsubscribe rates were mostly tame for content-type words, click rates weren't too great for "newsletter," "report," or "today" either.

Other Words

A few other kinds of words had a noteworthy impact as well.

  • Dates - The absolute best-performing word on the entire list was "daily." As much as intuition tells me that a daily update in the inbox is going to create burnout, the data tells a different story. It had the best click rate, 100 percent above average. Even more impressive, it managed to do that with the best unsubscribe rate on the entire list, 75 percent lower than average. If you take away one thing from this, it's that you should publish daily, as long as you can keep the quality standards high enough. "Weekly" also performed well, with a 51 percent above average click rate, and a 50 percent below average unsubscribe rate. "Monthly," on the other hand, did awful. So if you do publish monthly, don't point it out in your subject line.
  • Calls to Action - There were pretty much zero of these studied that did well. "Get," "register," and "subscription" all produced worse than average unsubscription rates, with subscription weighing in at 89 percent worse. Only "download" had a better than average unsubscribe rate, by 28 percent. It's click rate was 6.1 percent below average, though, so you're better off sending online content when the same value is possible.
  • "Don't miss" - Don't do it. It's 43 percent below average on clicks, and 33 percent worse than average on unsubscriptions.
  • "Re:" or "Fw:" - Are you insane? These created unsubscribe rates 91 and 135 percent worse than average, respectively. Those are the worst unsubscribe rates on the list. And that didn't even correspond to a good click rate. Those sat at 43 and 48 percent worse than average, respectively.
  • "iPad" - I view this as a good proxy for prize offerings, and the numbers aren't especially encouraging. The click rate is 20 percent above average, so nothing special. The unsubscribe rate is 20 percent higher than average, so not worth it.

The Takeaway

If you want to use email to retain your customers, you want to focus primarily on content, with its low unsubscription rates (as long as you stay away from "issues" and "webinars"). Stay away from scarcity tactics, and create an expectation for high quality, consistent content, ideally on a daily basis. Barring that, weekly content appears ideal.

When you do sell, use soft selling words, like "new." While "free delivery" and "sale" can pull in massive clicks, they also lead to horrendous unsubscribe rates. It's better to keep selling to the same people than to churn and burn them with over-the-top marketing messages.

As for formats, standard web content and videos seem to be the rule. Your audience doesn't want to sign up for a webinar or download a white paper. These are best as ways to collect the email address in the first place. They aren't the kind of thing you want to send to an audience you already have. When it makes sense, offering a "download" is the only sensible option.

Image credit: Jeremy Keith

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