(550 5.1.1 Relay not allowed APPLE) I can't send an email from a gmail address to a private apple address

Question

I set up my domain name and private email address in Certificates, Identifiers & Profiles. Both are SPF checked. I just want to send manually an email from my email(the one from certificate which matches bot private email and domain from Certificates...) to an apple generated private email which exists because I take it from my app after Apple Sign In. After sending an email I receive this error.

Answer 1

I've found a documentation link. It says you must register your domain to use relay service.

https://help.apple.com/developer-account/?lang=en#/devf822fb8fc