[sjau]

if you want to use some more checks you could also add this:

        reject_invalid_hostname,
        reject_non_fqdn_hostname,
        reject_non_fqdn_sender,
        reject_non_fqdn_recipient,
        reject_unknown_sender_domain,
        reject_unknown_recipient_domain,

Those are just standards checks on whether the email "appears" to be from a legit site.
In order to see whether you rbls work you can look at your mail.log and see if any of the lists rbls will appear in there.