

Update: Took the time to check "Handoff" with copying/pasting that email address between iOS and macOS. Perhaps, it happens with using non-native Safari and Mail.

However, I don't recall ever having this problem. I'll have to test it later but the mailto: redirection works on macOS that I'm sitting at right now. The "mailto:" function is removed whenever you select and follow the link Whenever the OS opens the default mail client from that link and inserts it into the "Send to" input, then it will automatically remove the "mailto:".

Whenever you context menu click to copy, then you're copying the entire string which includes the "mailto:" redirection. If you're using a context-menu and it has the option available, then selecting "Copy email address" does not copy the entire string as "Copy Link" or just "Copy" functions do.
