Notes:
smtpd_client_restrictions =
permit_mynetworks
permit_sasl_authenticated
check_client_access hash:/etc/postfix/access
reject_unknown_client
smtpd_etrn_restrictions =
permit_mynetworks
check_etrn_access hash:/etc/postfix/etrn_access
smtpd_helo_restrictions =
permit_mynetworks
check_helo_access hash:/etc/postfix/helo_access
check_helo_access pcre:/etc/postfix/helo_access_regex
reject_non_fqdn_hostname
warn_if_reject reject_unknown_hostname
smtpd_sender_restrictions =
check_sender_access hash:/etc/postfix/sender_access
reject_unknown_sender_domain
check_sender_mx_access hash:/etc/postfix/mx_access
reject_non_fqdn_sender
smtpd_recipient_restrictions =
permit_mynetworks
permit_sasl_authenticated
reject_invalid_hostname
reject_unauth_destination
reject_unknown_recipient_domain
check_recipient_access hash:/etc/postfix/recipient_access
check_recipient_mx_access hash:/etc/postfix/mx_access
smtpd_data_restrictions =
reject_unauth_pipelining