So naturally for all your emails you have in your inbox the sender has them in their outbox...and every email you sent also exists as a copy in somebody else’s inbox.
And you can’t control whether the other parties host their own email server or if they use a hosted service...in which case, guess what: now a third party also has a copy.
Now to hosting your own email server...who is gonna stop your Datacenter from obtaining a copy of your emails? They call it backups ;)
It’s easy to talk to your Barista about decentralization and blockchain as the solution to privacy...but actually making that a reality is not.
And we haven’t even touched on spam...how you gonna fight that in a decentralized network? How about bots?
I could go on but I hope you get the picture.