Why email and Nostr have a similar architecture.

Both are open, federated protocols where identity and infrastructure are separated. In email: your address is [email protected], servers (SMTP/IMAP) store and route messages, and any email client can talk to any server. In Nostr: your identity is your public key, relays store and route events, and any Nostr client can talk to any relay. Neither is owned by one company. You can self-host the infrastructure. The key difference is that Nostr replaces domain-based identity with cryptographic keys, which is strictly stronger.