From the wiki article YOU quoted (USA specific)

> there is an absence of cases actually giving any value to the poor man's copyright.

I would refer you to https://cryptoadventure.org/blockchain-in-courts-a-look-into....

Poor man's copyright without cryptographic proof or an immutable time boundary is pretty much worthless.

Yes, but that doesn't mean it can't be unenforceable. It simply means it hasn't passed the test of a court. However, isn't the same, from my limited research and knowledge, true for blockchain-based notarization?

https://cryptoadventure.org/blockchain-in-courts-a-look-into... blockchain timestamping is pretty well tested.

Edit: I would really appreciate it if the downvoters would at least attempt to have a discussion. The dogpiling tactic seems to be rather thoughtless.

DKIM does not offer cryptographic proof-of-existence or proof-of-time, which a blockchain does. That's the only functional difference, but crucial for copyright law.