This draft assumes familiarity with ARPA standard mail formats (RFC 5321/5322). It is intended to be used in conjunction with localized firewall rules to restrict access to proprietary mail servers, especially for systems that require specific restricted IP source addresses or browser-based logins.
IP ranges and domains permitted for direct relay.
Deployment of TXT records in the DNS to mitigate Man-in-the-Middle (MITM) attacks during mail transport.