It looks interesting as a hackathon project. I might be short sighted but how does this is YC S25 level good?

This looks like one of the easiest way to get your domain blacklisted in all the email providers.

I think its the energy and passion that YC is investing in. At times too much understanding stops you from doing things which may seem infeasible/wrong/illegal/unethical and one does not even goes in that direction.

However at scale or in some circumstances people may strike gold. Stripe is a good example I can think of, existing knowledgeable folks were scared of even getting into PCI compliance