I don’t buy this. I’m still using SMTP on my own domain and it’s working fine, a bit of spam but not unmanageable, real messages get read. Main challenge is digesting so many potentially-interesting list messages, indicating email’s continued dominance for professional topics. Seems this author has another agenda.
Having said that, it’s a pity the world never agreed a protocol for micro-payment for emails (and for many other services), which would resolve the spam problem, and not be a burden for honest users.