What is Apple Mail Privacy Protection (MPP)?

Apple Mail Privacy Protection (MPP) is a privacy feature introduced in iOS 15, iPadOS 15, and macOS Monterey in September 2021. When enabled, it prevents senders from knowing when an email is opened, where the recipient is located, and what device they're using.

MPP works by routing email content through Apple's proxy servers. Images (including tracking pixels) are prefetched automatically, regardless of whether the recipient actually opens the email. This triggers open tracking for messages that were never truly read.

For email marketers, MPP fundamentally changed the reliability of open rate as a metric. With Apple Mail commanding significant market share (often 50% or more of opens in consumer-facing lists), open data became inflated and unreliable for a large portion of subscribers.

The lighthouse still flashes, but you can no longer tell which ships are actually watching.