Last year, Apple’s iOS 15 update included Mail Privacy Protection (MPP). Devices with this update would automatically cause email service providers to register emails as “opened”. This has made the “open rate” KPI less reliable for email marketers.
In response, HubSpot has started providing adjusted open rates to offer a better estimate of the percentage of email opens. Naturally, I was curious and wanted to see how reliable this new metric is.
How Adjusted Open Rate Works?
HubSpot calculates an adjusted open rate for an email with this formula:
Reliable opens: opens by recipients on non-apple devices
Unreliable opens: opens by recipients that HubSpot suspects to have MPP enabled
Unique delivered: total number of unique deliveries of the email
Can We Rely On This Metric?
HubSpot makes sure to highlight that adjusted open rate is just an estimation. Since it’s not possible to definitely attribute unreliable opens to a bot or actual person, we should take this metric with a grain of salt.
However, since open rates are unreliable in general these days, this estimation can still provide some value when assessing a campaign’s performance.
