Using spamassassin + dovecot/postfix, how do you block messages from a blacklisted address instead of route to junk folder?

Question

I have set up an email server using a wizard tool, although I was hoping to alter the default behavior configuration such that when I receive emails from addresses I explicitly blacklist, those messages are immediately deleted as opposed to routed to the Junk folder.

I have currently been manually blacklisting addresses by adding blacklist_from address@domain.com to /etc/mail/spamassassin/local.cf and restarting the daemons. Is there a better method of doing this without using a particular client?

This my current rules for handling junk mail as set in contents of /var/lib/dovecot/sieve/default.sieve.

require ["fileinto", "mailbox"];
if header :contains "X-Spam-Flag" "YES"
        {   
                fileinto "Junk";
        }