How can I estimate real open rates with MPP?
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You can't get exact numbers on your open rate, but you can get closer with a few approaches.
Segment by email client. Most ESPs report opens by email client (Apple Mail, Gmail, Outlook, etc.). Pull out the Apple Mail segment and look at their open rate separately. Apple Mail Privacy Protection inflates opens for that segment, so you know those numbers are noisy. The open rates from Gmail and Outlook users are more reliable (though not perfect either, since some email clients do their own pre-fetching).
Use a ratio adjustment. If 40% of your list uses Apple Mail and they're showing an inflated 90% open rate, while the other 60% (non-Apple) shows 25%, you can apply a rough adjustment: assume Apple Mail opens are closer to the non-Apple baseline and calculate a weighted estimate. It's not precise, but it strips out some of the MPP inflation.
Look at click-to-open rate (CTOR) instead. CTOR measures clicks as a percentage of opens. Even with inflated opens, CTOR helps you understand what percentage of openers actually engaged. If your opens are inflated but your clicks stayed the same, CTOR will drop, which is a signal that the open count is noisy.
Use User Agent strings if your ESP exposes them. Requests from Apple Mail Privacy Protection come from Apple's proxy servers with identifiable User Agent strings. Some platforms let you filter these out to see only "real" opens, or at least separate them from proxy opens.
The honest answer is that there's no clean fix. Click-based engagement is your most reliable signal right now. If a campaign gets good click rates, that's real. If it gets good open rates but no clicks, that might be MPP noise.
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