I use RBL lists on my qmail server, how do I allow certain email addresses to bypass RBL?

assuming you're using tcpserver to block the blacklisted servers, have it instead set an environment variable, then test it in a shell script you invoke in place of qmail-smtpd.

The script either invokes qmail-smtpd or, if the variable tells it the server is blacklisted, invokes a modified version of qmail-smtpd that accepts email only to postmaster@ and abuse@ addresses.