Nostr has many issues with the decentealizatuon concept. And if we are honest Nostr is already some kind of centralized as we have not thousands of relays. You can solve the issue with spam with paid relays but then the whole concept is senseless

You can install it but it's a mission to maintain and ensure other large centralised providers accept your email (gmail and outlook).

I know this article but still you can install your own SMTP and use it