Email is currently more decentralized than Nostr is in practice.

"I have been self-hosting my email since I got my first broadband connection at home in 1999. I absolutely loved having a personal web+email server at home, paid extra for a static IP and a real router so people could connect from the outside. I felt like a first-class citizen of the Internet and I learned so much.

Over time I realized that residential IP blocks were banned on most servers. I moved my email server to a VPS. No luck. I quickly understood that self-hosting email was a lost cause. Nevertheless, I have been fighting back out of pure spite, obstinacy, and activism. In other words, because it was the right thing to do.

But my emails are just not delivered anymore. I might as well not have an email server.

(After self-hosting my email for twenty-three years I have thrown in the towel, Carlos Fenollosa, 2022)"

From the article, quoting this other article

https://cfenollosa.com/blog/after-self-hosting-my-email-for-...

If you do all the stuff (DKIM etc) AND you're not on a banned IP, you're fine. It seems like this person couldn't find a non-banned IP. I know plenty of people who self host email and successfully send to Gmail.

Yep. Know plenty of selfhosters who run email successfully. In fact, with all the email in a box packages out there, it's never been easier to self-host emails. One recommendation for those who are interested, is to choose a reputable VPS host with clean IP:s.

considering most people today only use 3 or 4 big email providers i can see the exact same happening for nostr, the p2p part seems more like a gimmick than a protocol requirement

It's actually advised to use 3/4 relays in your clients

Using NIP-65 (https://github.com/nostr-protocol/nips/blob/master/65.md) you can broadcast a note to the network to mention your preferred relays.

Most clients fetch that note when you first sign in and make sure you connect to your preferred relays