Email marketing has long been one of the most effective ways to reach and engage customers. For years, open rates have been the go-to metric for measuring the success of email campaigns, with marketers eagerly tracking how many recipients open their emails as a primary indicator of engagement. After all, if someone opens your email, they’ve at least shown some interest, right?

However, as the digital landscape evolves and email platforms become more sophisticated, open rates are becoming increasingly unreliable as a measure of engagement. In the UK, where inboxes are flooded with messages and privacy concerns are top of mind, it’s time to reconsider how we assess the effectiveness of email campaigns. Here’s why open rates no longer paint the full picture—and why businesses should start looking beyond this metric to truly understand how their emails are performing.

The Evolution of Email Tracking Technology

The main reason open rates are no longer reliable is due to changes in email tracking technology. For many years, email platforms have used a tiny, invisible image—called a tracking pixel—embedded within the email to detect when the message is opened. When the email is opened, the image is loaded from the server, which registers as an “open.”

However, modern email systems and privacy features have rendered this method increasingly ineffective. Many of today’s email clients—such as Apple Mail, Gmail, and Outlook—automatically block images by default or load them from cached data without actually opening the email. This means that even if someone reads your email, it may not count as an “open.” In fact, Apple’s Mail Privacy Protection (MPP), introduced in 2021, made it even more difficult to trust open rates. MPP prevents senders from knowing when an email is opened, and it can even mask the recipient’s location and device information.

The result? A sharp decline in the accuracy of open rates as a true reflection of engagement.

Privacy Features and Their Impact

As consumer privacy becomes a growing concern, especially in regions like the UK, privacy features are increasingly being introduced to protect users. While these features are vital for protecting personal information, they also have a direct impact on how email opens are tracked.

Apple Mail’s MPP, for example, causes inflated open rates. Since emails are preloaded and opened automatically in the background, every recipient who uses an Apple device can show as having opened the email—even if they never actually viewed it. This can create a false sense of success in your email campaigns, leading marketers to overestimate the true level of engagement with their content.

Similarly, other email providers, including Gmail, have implemented enhanced privacy controls that limit the ability to track when an email is opened. These shifts are driven by a growing public awareness of data privacy issues, with GDPR regulations in the UK and EU playing a key role in encouraging more protective email practices.

Engagement Is More Than Just an Open

While open rates can tell you whether an email has been opened or not, they fail to provide any insight into what happens next. An open doesn’t necessarily mean the recipient engaged with the content of the email. They might have clicked through to a website, responded to a call-to-action (CTA), or ignored the email altogether. Open rates also fail to account for the quality of engagement. A user may open an email, glance at the subject line, and immediately delete it without ever taking action.

True engagement goes far beyond just opening an email. It’s about:

• Click-through rates (CTR): Did the recipient click on any links or calls to action within the email? CTR offers a more accurate reflection of engagement, as it directly measures the recipient’s interest in the content.

• Conversions: Did the recipient take the desired action, such as making a purchase, signing up for a webinar, or downloading a resource? Conversions are the ultimate goal of most email campaigns and give a clearer picture of engagement.

• Time spent reading: How long did the recipient spend engaging with your content? If your email has a detailed offer or content piece, the time spent reading can be a much stronger indicator of interest than a simple open.

• Reply rates: In some cases, especially with more personalised or conversational campaigns, the reply rate can provide a clearer signal of engagement.

By focusing on these other metrics, brands can better understand the true impact of their emails.

A Changing Landscape of Email Clients

The growing use of mobile devices also impacts open rates. Many people in the UK now read emails on mobile devices or tablets, where images may not load immediately or at all. This can prevent the open rate from accurately reflecting engagement. With mobile-friendly emails becoming the norm, marketers need to understand that just because a message was opened on a smartphone, it doesn’t mean the content was absorbed or acted upon.

Moreover, some users may read an email but never fully engage. For instance, a customer might view an email’s subject line and preview text, but not actually open it. If marketers solely rely on open rates, they miss out on understanding how and why people engage with the content. The focus should be on how people interact with the content inside the email, rather than the fact that it was opened in the first place.

The Rise of New Metrics

As the limitations of open rates become more apparent, marketers are turning to other metrics to better assess engagement:

1. Click-Through Rate (CTR): CTR gives a more concrete picture of how well your email content resonates with recipients. By tracking the percentage of people who click on links within your email, you can measure how compelling and relevant your message is.

2. Conversion Rate: Ultimately, conversions—whether that’s a purchase, sign-up, or any other business goal—are what matter most. Tracking the actions users take after engaging with your email gives a clearer picture of success.

3. Engagement Rate: This includes a combination of metrics, such as clicks, replies, forwards, and social shares. It measures how recipients are interacting with your email content and can give you a much fuller picture of your email’s effectiveness.

4. Unsubscribe Rate: While often seen as a negative metric, the unsubscribe rate can still provide valuable insight into whether your emails are landing well with your audience. If unsubscribe rates spike after a certain campaign, it could indicate that your content isn’t resonating or that you’re over-saturating your audience.

5. Time Spent on Email Content: How long a recipient spends reading an email can give you a better understanding of whether they’re truly engaged with your content.

What Marketers Should Do Next

To move beyond the limitations of open rates, UK marketers should consider implementing a broader, more holistic approach to email performance measurement:

• Focus on quality over quantity: Rather than simply tracking how many emails are opened, focus on the actions recipients take. Did they click on a link? Did they convert? These are far more meaningful signals of engagement.

• Rely on multi-metric analysis: Don’t rely on a single metric, like open rates, to gauge success. Look at a combination of metrics, including click-through rates, conversions, and time spent engaging with your emails.

• Leverage A/B testing: Experiment with different subject lines, content, and CTAs to understand what drives the most meaningful engagement. A/B testing allows you to optimise your emails for better results, beyond what open rates alone can tell you.

• Embrace new technologies: Consider using email analytics tools that offer deeper insights into user behaviour, including how recipients engage with your emails after they open them. Some tools can track scrolling, time spent on email content, and even heatmaps to provide more context on engagement.

Conclusion

While open rates have long been a trusted metric for measuring email engagement, they can no longer be relied upon as an accurate measure of success. Changes in email client technology, increased privacy controls, and the rise of mobile devices have all rendered open rates less reliable. To get a true picture of how your emails are performing, it’s crucial to look at a range of other metrics, including click-through rates, conversions, and overall engagement. By adopting a more comprehensive approach to email measurement, UK marketers can make more informed decisions and create more impactful, customer-centric campaigns that drive real results.