So technically this is DKIM, except pushing the verification down from the domain level to the individual user level. And instead of publishing the public key in the DNS record, you manually give individual senders one/many time keys to send emails to you.
Wouldn't it be easier to just set up a whitelist for emails in your inbox, that only allows senders you specify through?
I'm not sure about your conclusion since that would violate the number one feature of email, but yes, the author's proposals do seem very unwieldy and ignore existing solutions.
Wouldn't it be easier to just set up a whitelist for emails in your inbox, that only allows senders you specify through?