The optimal email marketing frequency

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📝 Context

Topic: Customer Experience | Ecommerce
For: B2C. Can be tested for B2B
Research date: December 2017
Universities: University of Toledo, Indian School of Business, Indiana University.

You’re coordinating your email marketing to customers for promotions, new offerings, seasonal sales and other campaigns. As you do, you’re trying to decide the number of emails to send to maximize ROI.

Your instinct is probably to double down on your most loyal customers. If they have already bought, sending them a few more emails will probably nudge them to buy even more - right?

Wrong. Science says the opposite is usually true, and that less really is more when it comes to the link between emails and buying.

📈 Recommendation

When doing email marketing, send 12-14 emails monthly to people you think are less likely to buy, and only 5-7 emails to those most likely to buy from you.

If you’re unsure how likely someone is to buy, send around 7 emails monthly.

You will maximize sales and revenue per customer.

🎓 Findings

• Lifetime revenue from customers is higher when frequent buyers receive fewer marketing emails, and occasional buyers receive more emails.

• In an analysis of over 53,000 emails and 5,300 purchases by 200 customers at a US home improvement store over 3 years, researchers found the optimal number of emails to send monthly was:

  • 5-7 emails for heavy buyers

  • 6-10 for medium buyers 

  • 12-14 for customers who bought less frequently

• When customers weren’t segmented by how often they buy, 7 emails monthly led to the most email opens and most purchases over time.

  • Reducing this to 4 emails monthly led to 32% less lifetime profit per customer

  • Increasing this to 10 emails monthly led to 16% less lifetime profit per customer

🧠 Why it works

• While we do buy more after marketing emails, the dynamics are often reversed. If we buy frequently from a brand, we might ignore their emails as we know their offerings. In contrast, when we buy less often, we might read more emails, as we’re seeking information about the brand. 

• Similarly, after signing up for email alerts, our interest often declines the more we buy. When we’re not familiar with a brand, we might buy less but open more of their emails. As we become more familiar, we might buy more while ignoring their emails, because we feel we know what we want.

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✋ Limitations

• The study looked at the number of emails sent, without differentiating based on the content of the emails sent. The subject line, content, and relevance (e.g. giving personalized recommendations) would impact whether and how customers respond to the emails.

• The research looked at a random sample of 200 customers of a single US home improvement store selling in multiple categories (e.g., kitchen, plumbing, electrical, flooring, paint, outdoors). The optimum number of emails might differ for subscription-based services (e.g. Canva, Audible, Duolingo) or occasional large purchases (e.g. high-end electronics, travel packages). 

👀 Real-life example

Ecommerce giant Temu is a prolific emailer, often sending more than one email a day to customers.

❌ Issue: Sending so many emails to customers is likely to annoy them, leading to low open rates or higher unsubscribe rates.

✅ Solution: Temu can optimize their email marketing by:

• Linking the frequency of emails to how often a customer buys.

• Using customers’ purchase history, customers can be divided into tiers, with the number of emails sent monthly depending on the tier a customer falls in.

• Sending no more than 14 emails monthly (one every alternate day) to customers who buy the least. Frequent customers could be sent 1-2 emails per week at most.

• Using GIFS or emojis (but not both) for simple, direct and short messages (e.g. a discount or countdown for a promotion ending)

• Vary the fonts in their emails based on the products being highlighted, with handwritten fonts for pleasurable items and machine-like fonts for functional items.

🔍 Study type

Market observation (analysis of over 53,820 emails and 5,300 purchases from 200 customers of a US home improvement retailer over 39 months)

📖 Research

Dynamically Managing a Profitable Email Marketing Program. Journal of Marketing Research (December 2017). 

🏫 Researchers

• Xi (Alan) Zhang. University of Toledo

• V. Kumar. Indian School of Business

• Koray Cosguner. Kelley School of Business, Indiana University.

Remember: This is a scientific discovery. In the future it will probably be better understood and could even be proven wrong (that’s how science works). It may also not be generalizable to your situation. If it’s a risky change, always test it on a small scale before rolling it out widely.

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