That’s just Apple saying “hello” from Cupertino. Have you spotted other strange email headers? Share them in the comments—let’s decode together.
Apple Mail adds this header before handing the message off to your outgoing mail server. It’s not configurable in Settings, and it doesn’t affect deliverability. The Privacy Angle Because x-apple-i-md-m can contain a persistent device identifier, privacy-conscious users have raised concerns. Apple has not clarified whether this header is stripped when sending through iCloud mail servers (vs. third-party SMTP). x-apple-i-md-m
At first glance, it looks like a typo or a debugging artifact. But if you’re seeing this header, you’re likely looking at an email generated by an Apple device (iPhone, iPad, or Mac). Let’s pull back the curtain on this little-known signature. x-apple-i-md-m is a proprietary header added exclusively by Apple’s Mail application when sending email via an SMTP server that requires authentication. That’s just Apple saying “hello” from Cupertino
