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    Metrics

    Open Rate

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

    Open rate = (unique opens / delivered) × 100. Apple Mail Privacy Protection and other privacy features have made open rates less reliable since 2021 — they now significantly over-report opens for Apple users. Use open rate as a directional metric, not an absolute one. Click rate and revenue per email are now more meaningful.

    Related terms

    Click-Through Rate (CTR)

    The percentage of delivered emails where the recipient clicked at least one link.

    Apple Mail Privacy Protection (MPP)

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