Web links on the subject of SPF
On this page we present further useful links
Professional domain management for resellers and business customers. The complete solution for your domain portfolio.
Wikipedia
Very good summary of the topic Sender Policy Framework with theoretical and practical hints.
SPF project
Official site of the SPF project. Very extensive information and hints for DNS administrators in English.
RFC 7208
Sender Policy Framework Standard of the Internet Engineering Task Force, Version 1 in english.
