I feel like this is a solvable problem without making any changes to email whatsoever. The problem is the email recipient hosts are suspicious of the sender (as

I feel like this is a solvable problem without making any changes to email whatsoever. The problem is the email recipient hosts are suspicious of the sender (as opposed to the message itself being suspicious). So the solution is to have a standardized way for senders to acquire an instantaneous reputation by tying their real-world identity to it (which lets them be held accountable if they do spam), and perhaps by throwing some money at it too. If there was some company that did identity checks, similar to how EV certificates are given out, then that ties your real-world identity to it (this could in fact be done by literally requiring an EV certificate for the hostname of the sender). This company could also take a decent-sized deposit (so you're staking money on not being a spammer) and hold it in trust for a set amount of time. Once the time has passed, and you've sent enough emails for recipients to draw meaningful conclusions, if you have in fact not spammed, then you get your deposit back (minus a service fee). Then all the big email hosts would pay this company to query it about senders the host doesn't already trust, and similarly they'd report any spam from these hosts back to the service. Heck, this doesn't even have to be a new company. A big host like Google could just start offering this service anyway, as a way to simplify their own handling of unknown senders, although I'd feel more comfortable if this was done by someone else.