perfect marketing email

Research Report: How to Create the Perfect Marketing Email

Forget “digital marketing’s workhorse” – it’s time to acknowledge email as the prizewinning thoroughbred it really is. So what goes into creating the perfect marketing email?

Although flashier channels like social media and mobile marketing routinely steal headlines, email is still the core of every effective digital marketing strategy. The reasons are simple: it has enormous reach, and it works. According to an eMarketer forecast, the total number of email users in the US will reach 277.7 million in 2024, representing 81.2% of the US population. Plus, with cookies being phased out, email addresses (and their function as a unique identifier) are even more important.

Even tech-savvy millennials prefer to communicate with brands through email; 60 percent of respondents chose email as the preferred channel, while only about 13 percent each selected text messaging or social media.

The question is no longer whether companies should invest in email, but rather how to maximize its return. Consumers are inundated with marketing messaging at all hours of the day, and it’s easier than ever to get lost in the noise. Marketers must be strategic in building email messages that are optimized to convert.

As you might know, we’re big fans of data at Retention Science. We set out to find the key shared attributes of the best-performing emails in search of what makes up the “perfect” marketing email. We analyzed data from over 1 billion emails that resulted in 60 million orders over the last two years, from brands like The Honest Company, Diamond Candles, and Dollar Shave Club.

Here’s what we found:

Maximize Conversions With Percent-Off Deals


Dollar-off savings may seem like the most appealing promotions, but they’re not as effective as other types of deals. Our data shows customers are more receptive to percent-off deals with 38 percent of customers more likely to click, and 47 percent more likely to convert when they were presented with a percent-off offer vs. a dollar-off offer.

Novelty Items Spark Interest, But Not Sales

Subject lines that mention novelty items generate more interest, showing a 6 percent lift in open rates. We defined novelty items as big-ticket items like HDTVs, or special items that go with seasonal or partnership promotions. However, when it comes to featuring products in the email body, marketers should stick to the familiar. Common goods such as groceries and personal basics have a 10 percent higher click-through rate than novelty or specialty items, even when the novelty item was featured in the subject line.

The reason behind the discrepancy? Novelty items are good at catching the eye because customers want to stay on top of perceived deals on big-ticket or specialty items, but most people don’t tend to purchase unless there is a specific need. Basics, on the other hand, need replenishing on a more regular basis.

Punctuate Your Subject Lines!


Punctuation impacts email open rates. The presence of any type of punctuation mark increased open rates by 9 percent. Question marks are particularly effective at engaging recipients. In fact, the study found subject lines with question marks have open rates 44 percent greater than those with exclamation points.



Keep Subject Lines ASAP (As Short As Possible)

Six to 10 words is still the optimal length for email subject lines, ranking highest for open rates (21 percent) for the second year in a row. Second highest is five words or less, with a 16 percent open rate. The rates start to fall significantly in the 11 to 15-word range, with emails only opened 14 percent of the time, and results only decrease from that point.

“Consumers are sifting through tons of emails a day and making at-a-glance judgments about which to open and which to trash, so it’s vital to be descriptive and brief,” said Jerry Jao, CEO of Retention Science. “While six to 10 words is the sweet spot, our clients experimenting with even shorter subject lines, those in the one to two-word range, are seeing even more impressive results.”

Email Subscriptions Falter During Summer Months

Losing access to a customer’s inbox can be detrimental for marketers, which is why it’s imperative to know the times of the year customers are most likely to unsubscribe. In looking at the unsubscribe data over the course of a year, Retention Science found 28 percent of total unsubscribes occurred in August, the highest of any month. The holiday season saw fewest unsubscribes during the year – November accounted for 4% and December for 5% – likely because consumers are on the lookout for deals and gift ideas. Marketers may also want to amp up their efforts in April and October, which accounted for above-average amounts of unsubscribes (8 percent and 9 percent, respectively).

Click Rates Highest in October, Conversions Highest in July


While open rates are consistent throughout the year, click rates are highest at the beginning of the holiday season, reaching 30 percent in October and 27 percent in November. Likely due to Fourth of July holiday sales, July has the best conversion rate of any month, with rates 21 percent higher than average. December ranks second, with rates 10 percent above the norm.

There is, of course, no single email format that will magically convert 100% of the time. This is because each customer is different, and therefore what motivates each person to click on your email is slightly different. The truly perfect marketing email, then, is achieved through personalization, where each customer receives content and offers that have been optimized to their unique preferences. Still, the above insights will help boost your email marketing efforts to get you started on that path. Enjoy the ride!

Research Methodology

Retention Science analyzed more than 1 billion emails sent by a cross-section of retailers in the past two years. Results were normalized to account for varying sample sizes. The campaigns involved retailers involved in specialty goods, apparel, baby products, and wellness products, among others.


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