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    Metrics

    Apple Mail Privacy Protection (MPP)

    A privacy feature that pre-fetches every email image, making open rates unreliable for Apple Mail users.

    Launched in iOS 15 (2021), MPP loads all email content (including tracking pixels) on Apple servers as soon as a message arrives — whether or not the user actually opens it. This inflates reported open rates by 20–60% for senders with significant Apple Mail audiences. Modern ESPs offer "MPP-adjusted" open rate metrics; some have shifted to engagement scoring instead.

    Related terms

    Open Rate

    The percentage of delivered emails that were opened by the recipient.