Postfix was written in 1998. Dovecot in 2002. Roundcube in 2008. The foundation of SMTP — RFC 821 — dates back to 1982. As you read these lines, the world's digital communication infrastructure runs largely on software with some components now 44 years old. Why has the email stack been frozen for so long? And if we designed it from scratch today, could spam be made mathematically impossible?

https://panelica.com/blog/postfix-dovecot-roundcube-email-stack-stagnation