Sender Policy Framework (SPF) is an email validation and authentication protocol that helps prevent email spoofing, phishing, and spam. It allows domain owners to define a list of authorized mail servers that are permitted to send emails on their behalf. This list of authorized servers is published in the domain's DNS (Domain Name System) records.

Key aspects and functionalities of SPF include:

Authorized Mail Servers: SPF enables domain owners to specify the IP addresses or hostnames of servers that are allowed to send emails using the domain in the From address.

DNS Records: SPF records are added to the domain's DNS records, detailing the authorized servers and their configurations.

Verification Process: Receiving mail servers can verify the authenticity of an email by checking the SPF records of the sending domain and comparing the sending server's IP address.

Action on Failures: Depending on the SPF policy, a receiving mail server may choose to accept, reject, or mark an email as spam based on the SPF verification result.

SPF helps in ensuring that emails sent using a specific domain are genuinely from authorized sources, enhancing email security and trust in email communications.