Apple Mail seems to include a user‑agent string (x-mailer) in outgoing messages which exposes both the device model and the iOS version used. It’s worth mentioning this in the email clients guide so PG readers are aware of the potential device fingerprinting risk.
iOS shows:
- iOS/iPadOS version (from the build number),
- whether it’s an iPhone or iPad.
MacOS shows:
- mail app version (can reveal which macOS version is being used)
PrivacyGuides only recommends the MacOS version. I guess they could add that the header is removable in Terminal.
Open Terminal
defaults write com.apple.mail UserHeaders '{"X-Mailer" = ""; "Mime-Version" = "";}'
reload mail app