it will be a nice feature if you implement in the admin level a section to add, activate, deactivate differnt RBL servers.
At the moment the spam are horrible and if the customers add some forwarder to GMX, Hotmail, Web.de a.s.o. your server wil be added to the blacklist.
I did add the RBL servers manually to the main.cf (smtpd_recipient_restrictions)
This helped me a lot.
Yes i know i can use a listener, but i think this is a nice feature for the panel.