Email open rate is one of the most cited metrics in email marketing and one of the most misunderstood. Many founders track it as if it were a reliable measure of how many people are reading their emails, without understanding the technical limitations that make the data increasingly unreliable. Understanding what open rate measures, what affects it, and how to interpret it is important for anyone using email marketing seriously.
An email open rate is the percentage of delivered emails recorded as opened, typically measured by whether a tracking pixel in the email is loaded by the recipient's email client. The metric has become significantly less reliable as email clients — particularly Apple Mail — pre-load tracking pixels regardless of whether the email is actually read, inflating measured open rates. Open rate is best understood as a directional indicator rather than a precise measure of engagement.
Click-through rate — the percentage of recipients who click a link — is a more reliable indicator than open rate, as it reflects a deliberate action rather than a technical loading event. Tracking clicks, replies, and conversions provides a more accurate picture of programme performance. Our guide to email marketing metrics covers how to measure what actually matters and how to improve the numbers that do.