Sender Policy Framework

The final SPFv1 specification: RFC 4408

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This is the final specification for the v=spf1 record syntax and semantics. It is based on the last draft series, draft-schlitt-spf-classic, and was published by the Internet Engineering Task Force (IETF) on 2006-04-28.

Historical editions of the specification

SPF has a long history reaching back to mid-2003, when it was created as a spin-off from Gordon Fecyk's then-current Designated Mailers Protocol (DMP) draft. SPF was also strongly influenced by Hadmut Danisch's Reverse MX proposal.

In December 2003, the first stable SPF draft was released. Since then, a number of editions have been released, differing mostly in details, and leading up to the final specification published as RFC 4408.