Except there is no need for that whatsoever.
1. If you only want email relays to make onboarding easy, check how DeltaChat works.
2. If you want email to not depend on ICANN then the solution is fixing DNS not fixing SMTP, SMTP is fine. Nostr can't replace ICANN because there is no way to lookup a key to get MX records. I am working on this if you care at https://github.com/Nuhvi/mns
Of course if the purpose is to get funding from Nostr focused foundations, then it is pointless to argue about technology.
