How can I BLOCK email?

I am constantly getting spam email from McAfee in my spam folder How do I BLOCK them? I have created a discard rule, but I think it only applies to the inbox. Since the emails are in the spam folder, nothing happens. Is there a way to block them completely? I went into my spam folder today and had 74 emails, most from McAfee, and over 3 days old, so the discard rule isn't working.

How do I BLOCK emails?