To blacklist an alias: echo "alias@ketrenos.com reject" | sudo tee -a recipient_restrictions sudo postmap hash:/etc/postfix/recipient_restrictions sudo systemctl restart postfix To black list a sender: echo "name@address.com" | sudo tee -a sender_access sudo postmap hash:/etc/postfix/sender_access sudo systemctl restart postfix To add a sender (eg firsttechfed.com) to the whitelist of sender DNS: echo "firsttechfed.com OK" | sudo tee -a sender_access sudo postmap hash:/etc/postfix/sender_access sudo systemctl restart postfix To add a new list, append entries to /etc/aliases and run: echo "alias" | sudo tee -a /etc/aliases sudo postalias /etc/aliases sudo systemctl restart postfix