There's this myth that automated spam detection is hard because spammers are all very clever masters of disguise.

No. Spammers are stupid as a shoe. They have dog shit for brains.

Automated spam detection is hard because the line between spam and "legitimate" marketing activity is a fiction.

@danslimmon at least one email provider seems to err on the side of "That person who emails you three times a week mentioned a product, they must have suddenly turned into a spammer so we'll block them and not tell you"