The cloud services providers have some of the worst IP blocks for spam. Cheap hosting blocks are a distant second place. Google for example, doesn't even hide

The cloud services providers have some of the worst IP blocks for spam. Cheap hosting blocks are a distant second place. Google for example, doesn't even hide the fact you have to request whitelisting using their online business services portal. They don't give a toss what kind of sender authentication/signing hoops you have jumped through already, and user letters may still end up in the spam bin. Many users have indeed migrated to the web platforms, and don't care about people data-mining their business communications. The real issue is so have many spammers/scams, a side-effect keeping their trade on life support by removing technological administrative barriers for the desperate... and you can't block Google/Outlook/Redmond.