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May 8, 2017
Email Marketing  |  11 min read

8 Surprising Words That Can Hurt Your Email Open Rates

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Jake Johnson
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Why did the email go to the inbox? To get opened.

OK, dumb joke, but if you do email marketing, you know the pain of low open rates. A lot of time, energy, and resources go into crafting your email campaigns. When your open rates are low, it’s tempting to do this:

Dwight rage.gif

Goodness. Take a chill pill, Dwight.

What a difference a word makes

But you know what would be even more maddening? If all those low open rates were caused by using a few pretty common words in your subject line. Yeah, that would suck.

With that in mind, we analyzed 3.25 million broadcast emails from 24.3 thousand customer instances of our applications to determine what words hurt open rates. In simple terms, we compared emails that used a word in a subject line against emails that didn’t, accounting for similar accounts. (For the data geeks out there, you can read the testing methodology at the end of this post).

There were some surprising findings.

Turns out a word can make a big difference, and how it’s used can make an even bigger difference.

Here are eight surprising words that make a big (as in negative) difference in your email open rates.

“Last Chance”

We’re not talking about the rapper.

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(Who wouldn’t react to a surprise Beyoncé side hug that way?)

The word “Last Chance” was used in 30,000 broadcast emails from Infusionsoft apps. Turns out that only 26.7 percent of emails with the word chance performed better in terms of open rates than those without it.

About the only time we saw decent open rates with the word last chance was when it was paired with a first or last name, which spoke more to a general trend we saw in favorability towards personalized emails when it came to open rates.

TL;DR: Don’t take a chance with “Last Chance” unless it’s proven to work for your list. From our findings “Last Chance” reeks of desperation.


Out of 5,881 apps that utilize the word “Reminder” in email subject lines, less than half performed better, coming in at 46.9 percent.

The most common phrases that were employed were “final reminder”, “quick reminder”, “webinar reminder”, and “reminder today”.

This is one of those words that benefits from a pairing with urgency. Of all phrases, we found that “important reminder” performed positively. Out of 336 apps that employed it, 62 percent performed better than those that didn’t.

TL;DR: “Reminder” can work for you, as it did for almost half the Infusionsoft apps that used it. But you need to test the phrases you use it in to see what provides the best results.


When it comes to the word “Final,” one thing became clear out of our research—it doesn’t work when used to create a sense of urgency. Folks tune it out. The word appeared in 3,902 apps, and of those apps, only 41.3 percent had performance improvements.

Phrases that performed poorly included, “final call”, “final chance”, “final day”, and “final hour.” One statistically significant phrase that did result in performance improvements was “final detail”, which could speak to expected or waited for information out of pre-existing conversations.

TL;DR: The word “Final” more often than not doesn’t work well when used to create urgency in a subject line.


People like a good sale, right? That may be the case, but they don’t care much for email subject lines that contain the word “Sale.”

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Out of 5,731 apps that utilize the word, only 38.2 percent had performance improvements. Our research found that when presented in the context of a limited offer or a reduction in price there is a decrease in opened- ratio performance. This includes phrases like “Black Friday sale”, ”Cyber Monday sale”, “sale end”, “sale extended”, and “sale save”.

What can we make of this? There is probably no shortage of sale emails that hit inboxes in a given day. These require a special alchemy to result in an open. Your subject line needs to stand out and the prospect has to be in the mood and able to purchase. It’s not surprising these emails have lower open rates.

TL;DR: If you’re going to use the word “Sale” in a subject line, expect lower open rates. Try to be creative to stand out and increase your chances.


Much like “Sale”, the word “Save” performs poorly, with only 36.6 percent of the 4,716 apps containing the word in a subject line performing better than those that don’t.

We did take a look to see whether pairing the word with a quantifiable amount improved performance. For instance, if you used it like so: “save 50%” or “save $20”. Unfortunately, it didn’t. People like to save money, but they don’t respond well to email subject lines that indicate savings.

One statistically significant area where the word save works? “Save date”. People don’t want to miss an event, but they can do without your sale.

TL;DR: The word “Save” decreases open rates, even when paired with a specific offer.


This “Offer” is apparently something people can refuse.

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Of the 5,188 apps it appeared in, 45.5 percent performed better with the word.

Our research indicates that the performance of “Offer” depends on the phrases it is used in. The most common phrases were “offer end”, “special offer”, and “time offer”. Of those, only “offer end” was statistically significant in lowering open rates.

One pairing that performed well was “exclusive offer”, which performed better in 52 percent of the apps, though it did not occur in enough apps to make it statistically significant.

TL;DR: If you’re looking for an alternative to the word “Sale”, “Offer” is a good choice, but be careful how you use it.


Perhaps it’s time to discount the world “Discount” (and bad puns, eh?). Of the 3,101 apps that utilized this word in subject lines, only 38.9 percent performed better with the word than without it.

Common phrases for the word included, “early bird discount”, “discount ends”, “special discount”, and “discount code”. None performed especially well.

TL;DR: If your subject line contains the word “Discount”, there’s a good chance your prospects will discount it.


Many email marketers shy away from the word “Free” for fears that it increases chances of hitting the spam folder. After all, even this seagull knows there’s no such thing as free lunch.

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But there are times and places where the word gets used.

Out of 8,628 apps that used the word, only 40.7 percent performed better with it than without it. Phrases that hurt open rates include, “chance free”, “join free”, “free shipping”, “free live”, “tonight free”, and “free event”.

That being said, there are places where using the word “Free” anecdotally improves open rates. Those phrases include, “free copy”, “free ebook”, and “free download”. However, it’s important to note these were not statistically significant in our samples.

TL;DR: Most people are wary of the word “Free” in subject lines—plus it devalues your offer. Try to avoid it and be more creative. We found that using “Bonus” or “Gift” resulted in higher open rates.

Parting thoughts

There’s no hard and fast rule when it comes to what will or won’t work with your particular email list. Perhaps you’ve attracted all the people in the world who respond to the word “Free”. Or perhaps not.

As with any study like this, it’s important to use it as a guide that informs your own testing efforts. Play around with these words in different phrases in A/B tests, and see how they perform. If they work for you, then by all means, keep going forward.

Most lists will require constant change and refinement in the long run. One trick ponies don’t work. So even if something works today, it may start to diminish over time. Keep good records, test often, and you’ll find success.

Testing methodology

To conduct tests of significance between emails containing a certain keyword/phrase in the subject line and emails not containing those same respective keywords/phrases, a two-sided paired t-test was conducted for differences of median opened ratio for all groups of pairs that had the same app and similar batch processed sizes. In other words, broadcast emails with the same app and same bin of batch processed containing a specific word/phrase was paired with broadcast emails with the same app and same bin of batch processed not containing the particular word/phrase. The paired t-statistic was calculated using the differences of median opened ratio for each pair for all groups of unique levels of {app,bin}.

The level of significance was assumed to be:

image1.png = .05.

In addition to the t-statistic, two other measurements were utilized:

Percentage of bins that perform better with keyword/phrase than without keyword/phrase

For all groups of pairs for a specific word/phrase, the proportion of pairs where the median opened ratio performance was better for the group of emails containing that specific word/phrase than the group of emails not containing the specific word/phrase.

Weighted rank

The weighted rank for the sign of differences of each pair divided by the total size of the groups containing the specific word/phrase.


{0:neutral, -1: completely negative, 1: completely positive}

Weighted rank = image3.png


Screen Shot 2017-05-03 at 1.17.56 PM.png

Percentage of bins that perform better with keyword/phrase: 1/3

Weighted rank = image3.png


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