What I'm trying to tell you is hat this has de facto worked for me during the past 20+ years. I get ca. 100 spam mails a day and they all get neatly sorted in the spam folder. There is no server-side filtering at all, my email provider allows users to switch that off entirely (and better should because it's very faulty).
As I've said, I'm not interested in theoretical arguments. All of my domains wildcard forward to the same email address, too. Filtering client-side has never been a problem.
