Email open rate useful, but less honest than it used to be

How the pixel actually works

The tracking pixel is a tiny invisible image served from the sending platform's domain. When a mail client renders HTML and requests that image, the server logs it: which recipient, when, which message. That's an open. Simple, and it worked well enough for years. What changed is who fetches the pixel.

Why Apple's MPP broke the number

In 2021 Apple shipped Mail Privacy Protection on iOS Mail, macOS Mail, and the Apple Mail app on iPad. When enabled (and it's on by default), it pre-fetches every image in every email through Apple's proxies, whether or not the user actually opens the message. The pixel fires regardless. Your platform records an "open" that never happened. Outlook and Gmail have their own image-proxy behaviour that also distorts the signal differently.

The practical effect is open rates that look great while engagement quietly falls. A list of dead addresses can show a high open rate just from Apple's pre-fetch. That's why "we have 40% open rates" stopped meaning what it used to mean around 2022.

What you can still use it for

Open rate is still useful in three narrow ways. First, relative comparison across two campaigns to the same list, sent close in time, with the same subject-line style — the noise floor is roughly equal, so the delta is real. Second, identifying total non-engagement: if a list segment has effectively zero opens, those addresses are dead even after the pixel noise. Third, A/B testing subject lines, since the only difference between variants is the line itself.

Use click rate as your real signal

For actual engagement, click-through rate is the cleaner number. A click is something a human deliberately did. There are still bots (corporate security scanners click every link), but the noise floor on clicks is far lower than on opens. Pair CTR with reply rate where possible, and you have a better picture of engagement than open rate alone gives you.

How sendmsg.io reports it

We report open rate, with the caveat above understood. The dashboard surfaces it alongside CTR, bounce rate, and complaint rate so you don't anchor on opens alone. Engagement signals (clicks especially) factor into the reputation engine's view of how the inbox sees you — high engagement means mailbox providers trust your sending more, which keeps your inbox placement healthy.