What is RFC 7208 (SPF)?

RFC 7208 defines SPF (Sender Policy Framework), an authentication mechanism allowing domains to specify which IP addresses are authorized to send email on their behalf. Receivers check sending IPs against SPF records to verify authorization.

The RFC specifies SPF record syntax in DNS, mechanism types (ip4, ip6, include, a, mx), qualifiers (pass, fail, softfail, neutral), and processing rules. It defines how receivers should evaluate records and handle errors.

SPF provides foundational authentication by verifying the sending server is authorized by the domain in the MAIL FROM or HELO. Combined with DKIM, SPF enables DMARC alignment verification that protects against domain spoofing.

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