root@mxbackup ~ # cat /etc/postfix/main.cf
relay_domains = $mydestination my.domain1 my.domain2

smtpd_client_restrictions =
        permit_mynetworks,
        reject_unknown_reverse_client_hostname,
        reject_rbl_client zen.spamhaus.org,
        reject_rbl_client bl.spamcop.net,
        reject_rbl_client cbl.abuseat.org,
        permit

smtpd_helo_restrictions =
        permit_mynetworks,
        reject_invalid_hostname,
        reject_unknown_hostname,
        permit

smtpd_sender_restrictions =
        reject_non_fqdn_sender,
        permit_mynetworks,
        reject_unknown_sender_domain,
        permit

smtpd_recipient_restrictions =
        reject_non_fqdn_recipient,
        permit_mynetworks,
        reject_unknown_recipient_domain,
        reject_unauth_destination,
        permit

smtpd_data_restrictions =
        reject_unauth_pipelining