"Reversed" spam filter - it works !

I am receiving 20-40 spams every day, and have found nothing that helps.
Most solutions are worse than the problem.

However, this works :

1. Make mail rules that automatically sends all emails from known sources to special subfolders of the inbox.
2. Make an additional subfolder of the "inbox", for all personal email that escapes the former rules, called e.g. "unanswered".
3. Download email - to the inbox.
4. Single out personal email in the inbox and move it to the "unanswered" subfolder.
5. Delete the rest of the email in the inbox.