Email open rates are the most watched metric in email marketing and one of the least understood.
Most people read their open rate as a simple measure of success: high open rate means good, low open rate means bad. Improve the subject line, improve the open rate, everything gets better.
This is not quite right. Here’s what open rates are actually telling you and what they aren’t.
What open rates measure is the percentage of emails that were opened by at least one device, detected by the loading of a tracking pixel embedded in the email. Since Apple’s Mail Privacy Protection launched in 2021, any email opened in Apple Mail — which represents a significant portion of email clients — automatically triggers the tracking pixel regardless of whether the human actually opened the email. This means open rates are inflated and increasingly unreliable as an absolute metric.
What open rates are actually useful for is relative comparison. Is this email getting more opens than that email? Is this subject line outperforming that one? Is this list more engaged than that one? The direction of the metric is still meaningful even if the absolute number isn’t.
What open rates don’t measure: whether the email was read, whether the content resonated, whether the reader took any action, or whether the email generated any revenue. You can have a 60% open rate on an email that generates zero clicks and zero clients. You can have a 15% open rate on an email that generates ten client inquiries.
The metric that actually matters is click-through rate on emails that contain a call to action. Clicks are a proxy for engagement that can’t be gamed by privacy protection. If someone clicks a link in your email, they read it, found something relevant to them, and took action. That’s what you’re trying to create.
Beyond that, reply rate is arguably the most meaningful metric for service businesses. Replies require genuine engagement — the reader read the email, had a response, and typed it. A 2% reply rate on an email is extraordinarily high and represents real conversations with potential clients.
Watch the click-through rate. Watch the reply rate. Watch the unsubscribe rate after each send. Use open rates to compare, not to evaluate absolute performance.