I really don't get this. I use eXpurgate which works by monitoring thousands of email addresses for incoming similar emails and rejecting emails during SMTP delivery. I have seen zero spam mails in 20 years and there have also been zero false positives that I know of. So it seems to me that spam is in principle a solved problem, it's just spam filters that try to classify individual emails by machine learning that to this day do not work reliably. Still most providers insist on using filters that work this way.