The Most Useful (Sometimes Overlooked) Email Marketing KPIs

There’s no question about it—email is an essential marketing channel for brands around the world. While some consumers may gripe about inbox overload, studies continue to show that email still captures their attention, with 58% of adults reportedly checking their email first thing in the morning and 72% choosing email as their preferred method to receive brand communications.  To go one step further, according to Adobe, millennials are the most likely demographic to check their email numerous times in a given day: 70% from bed (who doesn’t, right?), 57% from the bathroom (wash your hands, please), and even 27% while driving (hopefully hands-free, beep-beep). All of these data points add up to abundant opportunities for brands to make an impression and drive conversions via email.

Yet it’s not enough to simply send beautiful and relevant emails. Measurement lies at the heart of all successful marketing campaigns. But, which email marketing KPIs (key performance indicators) really matter and why? Beyond the basics of measuring conversion, click-through rates, bounces and list churn, we dug a bit deeper to revisit email marketing metrics to look for other KPIs that are not as often measured, but just as critical.


Marketers are likely well aware that nearly half of all emails in the United States are now read on mobile devices, making responsive email design a must. Yet, it is still important to know what devices YOUR specific email subscribers are using. Depending on your target audience, the devices and email clients used may be over or under the national statistics. Additionally, segmenting your list to measure which platforms earned the highest engagement and conversion may provide valuable insight into the customer journey experience and areas that need improvement. For example, you may identify that while more mobile users click on email call-to-action buttons, desktop users actually convert and purchase at a higher rate – highlighting a gap in your mobile website experience that if optimized could greatly impact ROI.

Example Screenshot – Devices & Clients Breakdown
Example Screenshot – Devices & Clients Breakdown



It is widely known that email open rates can be a misleading, inaccurate, and often unreliable metric. That’s because typically open rates are counted by tracking when the images embedded in outgoing emails are viewed or whenever a link is clicked. But because many webmail services and email clients block images by default, many ‘opens’ may actually go uncounted.  Additionally, if the recipient uses a preview pane to scroll through their inbox, an email viewed briefly will be counted as an open even if the content was never read. For these reasons, tracking open rates only makes sense when comparing emails sent by the same brand to a similar group of recipients, but are not recommended for benchmarking across an industry. The Click-To-Open Rate is more widely used as an accurate assessment of email performance.

One metric you might not yet be measuring is read rate. Essentially, this KPI measures what happens between an open and a click, specifically how long the recipient engages with an email. This rate is typically broken down by three different time intervals:

  • Read – the consumer engaged with the email for eight or more seconds
  • Skimmed – engagement lasted from two to less than eight seconds
  • Glanced/deleted – engagement lasted less than two seconds

In IBM’s 2016 Email Marketing Metrics Benchmark Study, more than half of emails sent were classified as read (52%), followed by glanced/deleted (26%) and skimmed (22%). By measuring your specific read rate and segmenting further by device and email client, you can follow the customer experience journey and identify trends to help optimize your email and landing pages. Do significantly more mobile users glance/delete? Perhaps looking at implementing a responsive design or changing the time your email is sent could impact read rate.

If 8 seconds doesn’t seem like a lot of time to you, keep in mind that attention spans have gotten dramatically shorter. From 2000 to 2015, Microsoft researchers found that the average adult attention span dropped from 12 seconds to eight seconds, meaning humans now have shorter attention spans than goldfish. (You must be a super-human to have read this far!)



It may sound like a no-brainer, but another important metric to watch is the growth in the number of subscribers to your various lists. Often marketers spend more time on the actual email communications, and less time working on tactics for adding new subscribers to the top of their funnel. List churn typically ranges between 25-30% every year, making setting goals and measuring your growth rate essential to staying ahead of the effects of churn.

Calculate your monthly subscriber growth rate as:
Growth – Loss (or # New Subscribers – # of Unsubscribers – #Hard Bounces) / Previous Month’s List Size * 100




When subscribers continue to receive your emails, but for whatever reason don’t open them and don’t unsubscribe… maybe they’re just not that into you. What’s a marketer to do?

Obviously, there is a cost involved in sending emails to inactive subscribers, but it’s not only a financial hit. Sending emails to unengaged subscribers can actually hurt the deliverability of your entire email campaign because some email clients and Internet Service Providers are able to decipher which email senders have low engagement rates, and may delay sending your email, send it straight into the Junk/Clutter folder or worse, blacklist your entire domain. Blacklisting is just one danger (among many) that could result from buying an email list (don’t do it!).

The timeframe used to define an inactive subscriber will depend on your email frequency. For a list receiving 1 email a week, a 6-week review might make sense. For less frequent or more frequent emails, adjust accordingly. Overall, it’s critical to watch your engagement rate and attempt to re-engage inactive subscribers before purging.

Over To You

What other email marketing KPIs do you feel are important, but sometimes overlooked? If you are already tracking these KPIs, what have been some of the learnings you’ve seen?  Please share in the comments.

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