This is the opposite of other contacts where the contact URL has to be entered and then they can be followed or stop being followed which doesn’t apply to mail contacts. Additionally, mail contacts can’t follow back, they will only receive posts that is personally addressed to them.

Last but not least, mail contacts aren’t meant to be shared between Friendica users through a public record.

Thank you for the workflow description though, it helped me figure out exactly how these contacts are different.