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If you want to sell something in big numbers via email marketing, you’d better make it dull and boring.

That’s one (over-simplified) finding in a new study from Retention Science, which collected data from 1 billion emails over the course of the last two years. According to this study, novelty items don’t generate the kind of sales one might expect.

So what do we mean by “novelty items” in this context?

“We define novelty items as products that are marketed/promoted for special campaigns, be it seasonal items, partnership promotions, or promotions that coincide with some other big event,” Jerry Jao, CEO of Retention Science told me. “We also define them as big-ticket items, like TVs and other higher-priced electronics.”

Why do vanilla purchases fare better than sparkly promotions?

“Hot topic, seasonal, and time-sensitive items catch the eye of shoppers in their inboxes, but when it comes to final purchase, they tend to stick to the more ‘basic’ items they really need, buy often, and are not necessarily special,” Jao said. “Similarly, if the email subject line teases sales or offers on these big-ticket, expensive items, more people are likely to click, but won’t actually complete purchase on those items. People like to be on top of any perceived deals on big-ticket items, but don’t tend to purchase unless there is a specific need.”

The research shows some interesting trends in what does and doesn’t work in email promotion — still the channel with the highest return on investment in marketing.

Subject lines, for example, perform best when kept short.


Six to 10 words is the optimal length for email subject lines, ranking highest for open rates (21 percent). Second highest is zero to five words, 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. Anything longer than that causes the open rates to drop further.

Another key finding is that your choice of punctuation in subject lines 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.

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My own research on personalization in marketing shows that people will give up their email address for either a guarantee of an offer, or for absolutely no reason at all! Promises or weak offers perform least well. I wondered how my findings aligned with the data Retention Science has access to.

“That’s an excellent point, and while I don’t have hard numbers that align specifically with your research, I would say that we see a very similar trend overall,” Jao said. “Email collection, after all, is about effectively targeting the type of people who come to your site. While this is a generalization, I’d say it’s pretty accurate to state that people come across your site for one of two reasons. Someone purposefully went to your site based on referral, marketing/content, or some sort of existing interest in your brand, or someone found your site while searching for a specific item. The latter need strong offers to entice them to convert/give up email addresses, because they are likely looking at other options. The former are already interested in the brand, value proposition, or story — they therefore don’t need much encouragement, or any at all.”

In the end, it comes down to that oldest of sales adages — providing value.

“Weak offers or promises don’t register with either group in terms of value, so companies should work on their branding/story to entice the first kind of customer, but also provide compelling enough offers to at least get the second type of prospective customers through the door,” Jao said.

Regardless which email service you choose to use — and there’s a metaphorical minefield of choices available to the budding email marketer right now — the advice gathered from 1 billion sales-oriented emails is clear.

Keep it short. Ask questions. And push items that people both need and value, not the shiny objects they might want but ultimately decide not to buy.

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