[dingleberry420]

For what it's worth, I'm a google workspace administrator and we've had issues with legitimate business emails going to our spam folders. We used various tools in the workspace admin console to whitelist the sender, but their mails kept going to our spam. We contacted google support, they verified our settings were correct, then kind of shrugged and said they can't explain why gmail flags things as spam. They clarified that it wasn't just that they weren't allowed to tell me, but that it was literally impossible for them to know.

So I'm not sure if there is such a thing as a "quality score", but there certainly is a machine learning black box.