Are you being paid to let SPAM through?
Since Yahoomail is literally the very worst at filtering SPAM and very obvious scam emails, I've heard lots of people seriously suggest that you're being paid off by scammers to let their emails through. The filters we set up don't work, the **** scam emails are screaming in your face obvious and I know you're seeing them. People are actually talking about Yahoomail being on the take so set the record straight! I've been asking someone I know in the FBI and they may be investigating this.