Sender Policy Framework (SPF) is an email authentication method designed to detect forged sender addresses in emails (email spoofing), a technique often used in phishing and email spam.
SPF allows the receiver to check that an email claiming to come from a specific domain comes from an IP address authorized by that domain’s administrators. The list of authorized sending hosts and IP addresses for a domain is published in the DNS records for that domain.
Sender Policy Framework is defined in RFC 7208 dated April 2014 as a “proposed standard”.