Miscellany

#  Force proper EHLO/HELO introductions
smtpd_delay_reject = no
smtpd_helo_required = yes
smtpd_helo_restrictions =
        permit_mynetworks,
        check_helo_access hash:/etc/postfix/helo_access,
        reject_non_fqdn_hostname,
        reject_invalid_hostname,
        permit
#  Reject invalid senders
smtpd_sender_restrictions =
        permit_sasl_authenticated,
        permit_mynetworks,
        reject_non_fqdn_sender,
        reject_unknown_sender_domain,
        permit
#  More expensive tests
smtpd_recipient_restrictions =
        reject_unauth_pipelining,
        reject_non_fqdn_recipient,
        reject_unknown_recipient_domain,
        permit_mynetworks,
        permit_sasl_authenticated,
        reject_unauth_destination,
        check_sender_access hash:/etc/postfix/sender_access,
        check_recipient_access hash:/etc/postfix/recipient_access,
        check_helo_access hash:/etc/postfix/secondary_mx_access,
        check_policy_service inet:127.0.0.1:60000,
        permit