The definition of spam changed. Originally, it was scattershot bulk email, where the sender would just send to any address they had ever acquired for any reaso

The definition of spam changed. Originally, it was scattershot bulk email, where the sender would just send to any address they had ever acquired for any reason. Now spam means "anything the user doesn't want to receive". Even if the user previously deliberately created a relationship with the sender. Gmail successfully trained users into clicking the spam button for anything such. People just click Gmail's magic make-it-go-away button for things as legitimate as a mailing list they deliberately signed up for and are simply too lazy to properly unsubscribe. Legitimacy isn't a binary either-or, it's a continuum. You bought from a merchant ten years ago and they email you again, is that spam? How about the company that acquired that merchant which is now trying to sell you a completely different line of business? You donated to a politician and now their successor in the same party emails you, is that spam? That's what modern spam filtering deals with.