Apple implemented a privacy update for their mail app as part of iOS 15.

This update entails Apple opening all emails that are routed through their mailbox app (regardless of ESP) and then rehosting them on a proxy server.

By Apple opening all of the emails, it is intended to help ensure privacy for the end user, but from an email marketing standpoint, does make accurately tracking opens more difficult. To combat this to the best of our ability, our system detects and removes any opens that it identifies as coming from apple proxies so that they are not included in our opens tracking.