Are open rates accurate?

If you've ever celebrated a 60% open rate, there's a good chance you were partly celebrating your subscribers' email clients doing automated housekeeping. Open rates have never been perfectly accurate, but right now they're more noise than signal for a lot of senders.

Here's how open tracking actually works. Your ESP embeds a tiny invisible image (a tracking pixel) in each email. When that image loads, it counts as an open. The problem is that image can load without a human ever reading your email. Security scanners fetch it to check for malicious content. Corporate gateways pre-load it to scan for threats. And since September 2021, Apple Mail's Mail Privacy Protection (MPP) pre-fetches every image in every email, automatically, before a subscriber even opens the message.

That last one is the big one. Litmus data has consistently shown Apple Mail handling 40 to 55% of email opens tracked across their user base. If even half your Apple Mail recipients trigger a phantom open, your reported open rate can be inflated by 20 percentage points or more. Some senders saw their open rates jump 10 to 20 points overnight when MPP rolled out. That's not engagement. That's automation.

And it's not just Apple. Outlook and Google Workspace both have image pre-fetching or security scanning behavior that can trigger pixels, too. The scale is smaller, but it adds up.

So what can you actually trust?

• Clicks are a much stronger signal. A human has to actually interact with a link for that to fire (though bots do click, too, so watch for patterns like instant clicks from the same IP).
• Trend direction still matters. If your open rate drops sharply month over month with no obvious change in list composition, something real has likely shifted, even if the absolute numbers are off.
• Relative comparisons are still useful. Comparing segment A to segment B, or subject line A to subject line B, is valid as long as both are affected by the same noise sources in roughly equal measure.

What you shouldn't do is set an "open rate threshold" to trigger re-engagement campaigns or suppress contacts. If someone is being counted as an opener purely because MPP pre-fetched your pixel, suppressing them based on non-opens, or keeping them active based on phantom opens, both lead to bad list decisions.

The honest answer is that open rates still have some use, just not as a precise metric. Treat them like a barometer. They tell you if pressure is rising or falling, but they won't tell you the exact temperature.

If you want metrics that actually reflect engagement, clicks, replies, conversions, and unsubscribe rates are all closer to the truth. Those are worth building your decisions around.