Something

smtpd_client_restrictions =
        permit_sasl_authenticated
        permit_mynetworks
        check_client_access regexp:/etc/postfix/checks/white_list
        check_client_access regexp:/etc/postfix/checks/rejections
smtpd_sender_restrictions =
        permit_sasl_authenticated
        permit_mynetworks
        check_recipient_access regexp:/etc/postfix/checks/white_list
smtpd_recipient_restrictions =
        permit_sasl_authenticated
        permit_mynetworks
        check_recipient_access regexp:/etc/postfix/checks/white_list
        reject_non_fqdn_recipient
        reject_unauth_destination
        reject_unauth_pipelining
        reject_invalid_hostname