It’s in the headers. Send an email to your self from Mail and open the source in the inbox. There is your IP.
Using Mail: Version 16.0 (3864.600.51.1.1).
Sent from a Google Apps mail.
Have you tried a VPN? I wonder, if Apple manages to expose IP despite a VPN. They had issues with stuff like that before.
I'm not actually doubting it. saagarjha knows his stuff. I just don't see it, so maybe I'm holding it wrong.
I would need to test with my hosting Webmail client, so maybe tomorrow.
I’ll mess around, today, and see what comes up.