https://app.knowbase.one/vault/rfc/docid/7826
RFC7208: Sender Policy Framework (SPF) for Authorizing Use of Domains in Email, Version 1
Internet Engineering Task Force (IETF) S. Kitterman Request for Comments: 7208 Kitterman Technical Services Obsoletes: 4408 April 2014 Category: Standards Track ISSN: 2070-1721 Sender Pol...