That RFC by definition doesn't apply to domains that don't support email. Right in the abstract is this line: > ...organizations which support email exchanges

That RFC by definition doesn't apply to domains that don't support email. Right in the abstract is this line: > ...organizations which support email exchanges with the Internet are encouraged to support AT LEAST each mailbox name These recommendations are all for domains that don't run mail servers. If you do have a mail server, then yeah it is best practice to have those present but these recommendations won't apply to you.