You didn't even know what a pgp key was before this convo or read receipts, you have no idea what you're talking about. This is not a real problem and is already solved with outbox emails.

Your personal email server doesn’t count, because you can alter the log to show whatever you want. Nobody is going to take your word for it.

Falsifying evidence is a crime.

Manager tells worker they need to cover an emergency on the weekend, worker claims they never received the message.

Lol then the manager will say "why did you not respond", it's on the worker. They're not going to pull up a fucking blockchain, they're going to pull out their phone and say "see, I sent you this".

Business wants to cancel a work order, contractor shows up and says they weren’t properly notified of the cancellation.

That's the contractors fault. Blockchain is irrelevant. If they didn't check their email, they're sure as hell not going to check a dumb ass blockchain.

They know they sent you the message, even if you delete it or otherwise pretend they didn’t.

Crazy, I wonder how they know that? Maybe because they know they pressed the "send" button, and it's the other party's responsibility to accept.

Again, none of these situations need a dumb fucking blockchain.

You do understand that not every blockchain system is public, right?

https://www.blockchain.com/explorer