Someone

smtpd_recipient_restrictions =
        check_client_access hash:/etc/postfix/helo_client_exceptions
        check_sender_access    hash:/etc/postfix/sender_checks,
        reject_invalid_hostname,
        reject_non_fqdn_hostname,
        reject_non_fqdn_sender,
        reject_non_fqdn_recipient,
        reject_unknown_sender_domain,
        reject_unknown_recipient_domain,
        permit_mynetworks,
        reject_unauth_destination,

# Add RBL exceptions here, when changing rbl_client_exceptions, this
# file must be regenerated using postmap <file>, to generate a
# Berkeley DB

        check_client_access hash:/etc/postfix/rbl_client_exceptions,
        reject_rbl_client cbl.abuseat.org,
        reject_rbl_client sbl-xbl.spamhaus.org,
        reject_rbl_client bl.spamcop.net,
        # reject_rhsbl_sender    dsn.rfc-ignorant.org,
        # check_policy_service inet:127.0.0.1:60000
        permit