smtpd_recipient_restrictions =
        permit_mynetworks,
        reject_unknown_recipient_domain,
        reject_unauth_destination,
        reject_rbl_client sbl.spamhaus.org,
        reject_rbl_client dnsbl.sorbs.net,
        reject_unknown_sender_domain,
        reject_invalid_hostname,
        reject_non_fqdn_sender,
        reject_non_fqdn_hostname,
        reject_non_fqdn_recipient,
        permit