Detecting spammers with artificially generated target class
Machine learning is the process of automatically discovering (inductively) the formula/rule that models a certain random variable. If you can discover the rule by yourself, you don't need the machine to aid you.

You (or your boss), as the domain expert, has written a rule to model the target class. As long as this rule is deemed good enough for the business, there's no need to spend resources to generate another model.