Run something like the following:

postconf -e "permit_mx_backup_networks = /etc/local-COMMON/postfix/mx_networks"
postconf -e "maps_rbl_domains = `cat /etc/local-COMMON/postfic/rbl_lookup_hosts"
postconf -e "smtpd_recipient_restrictions = permit_mynetworks,permit_mx_backup,reject_non_fqdn_recipient,reject_unauth_destination,reject_maps_rbl,reject"