What they got wrong --- the Screener doesn't prevent spam and it consumes a lot of my time with the screening. What I want is real privacy --- reject anything

What they got wrong --- the Screener doesn't prevent spam and it consumes a lot of my time with the screening. What I want is real privacy --- reject anything that isn't from an "allowed address list". The "allowed list" gets updated by either sending an email to the address or by sending an email to myself with the address to be added as the subject line. To delete an address from the list, send to myself but use a minus (-) as the first character followed by the address in the subject line. Use the word "List" as the subject to receive a follow up email with the current allowed address list. Why would this not work to totally eliminate spam?