Open rate is the share of sent emails recorded as opened, a metric that used to signal recipient engagement but is now inflated by privacy features and security scanners that load a message's images before a human sees it.
Open rate works off a tracking pixel, a tiny image loaded when a message is opened. That mechanism used to make it a reasonable proxy for attention. It stopped being reliable once mail systems started loading images automatically, before any human involvement, which is now common enough to make the raw number close to meaningless on its own.
Apple's Mail Privacy Protection pre-loads every image in an email, tracking pixels included, on Apple's own servers before a person ever opens the message. Postmark, an email infrastructure provider, has documented that this can push measured open rates toward 100 percent for Apple Mail recipients, whether anyone actually read the email or not. Corporate security gateways scan and pre-fetch content the same way, before a message ever reaches an inbox. A number on a dashboard can reflect infrastructure behavior more than it reflects human interest.
The metric hierarchy that still holds up puts open rate below three others: reply rate first, positive reply rate second, someone who wants to talk rather than just anyone who replied, and meetings booked third. None of those three get faked by a privacy feature loading an image server-side.
Open rate still gets watched as a directional, secondary number, mostly to spot something badly broken, like a subject line that isn't rendering. It shouldn't be the metric that decides whether a test won or a campaign is working, since a rising number can just mean more Apple Mail or corporate-gateway recipients in the mix that week, not more actual interest.
A high or climbing open rate gets read as proof a subject line or send time is working. It might be. It might also just be the recipient mix shifting toward more Apple Mail addresses or more corporate security gateways, both of which report an open with zero human involvement. The number moving doesn't tell you which one happened.
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