smtpd_delay_reject = yes
#strict_rfc821_envelopes = yes
# Above is optional
smtpd_helo_required = yes
smtpd_helo_restrictions =
        permit_mynetworks,
        check_helo_access
                hash:/etc/postfix/helo_access,
        reject_non_fqdn_hostname,
        reject_invalid_hostname,
#       reject_unknown_hostname,
#can cause high rejection of valid mail
        permit
disable_vrfy_command = yes
smtpd_sender_restrictions =
        permit_sasl_authenticated,
        permit_mynetworks,
        reject_non_fqdn_sender,
        reject_unknown_sender_domain,
        permit
smtpd_recipient_restrictions =
        reject_non_fqdn_recipient,
        reject_unknown_recipient_domain,
        permit_mynetworks,
        permit_sasl_authenticated,
        reject_unauth_destination,
# ABOVE ENTRY REQUIRED to prevent open relay!
        reject_rbl_client list.dsbl.org,
# Above line rejects open relays
        reject_rbl_client zen.spamhaus.org,
# Above line rejects based on spamhaus listing
#        check_policy_service unix:private/policy
# Above line for greylisting (install postgrey)
#        check_policy_service inet:127.0.0.1:10023
# Above line for SPF check (install an SPF checker)
        permit
smtpd_data_restrictions =
        reject_unauth_pipelining
        permit