main.cf

# You can put the following access restrictions that the Postfix SMTP server
# applies in the context of the RCPT TO command
smtpd_recipient_restrictions =
    permit_mynetworks
    permit_sasl_authenticated
    reject_non_fqdn_helo_hostname
    reject_invalid_helo_hostname
    reject_invalid_hostname
    reject_unauth_destination
    reject_unauth_pipelining
    reject_non_fqdn_sender
    reject_non_fqdn_recipient
    reject_unknown_sender_domain
    reject_unknown_recipient_domain
    check_client_access hash:/usr/local/etc/postfix/access
    reject_rbl_client zen.spamhaus.org
    reject_rbl_client cbl.abuseat.org
    permit