Following the Zimbra Admin Guide I enabled the RLB's with the following command:

zmprov mcf zimbraMtaRestriction reject_invalid_hostname zimbraMtaRestriction
reject_non-fqdn_hostname zimbraMtaRestriction reject_non_fqdn_sender
zimbraMtaRestriction “reject_rbl_client dnsbl.njabl.org” zimbraMtaRestriction
“reject_rbl_client opm.blitzed.org” zimbraMtaRestriction “reject_rbl_client
relays.ordb.org” zimbraMtaRestriction “reject_rbl_client cbl.abuseat.org”
zimbraMtaRestriction “reject_rbl_client bl.spamcop.net” zimbraMtaRestriction
“reject_rbl_client dnsbl.sorbs.net”

How can I tell if these rules are working? Does it log when an incoming email matches an entry?