What is the purpose of Sender Policy Framework (SPF)?

The purpose of Sender Policy Framework (SPF) is to list authorized email servers for a domain. SPF is a protocol used by domain owners to specify which mail servers are permitted to send email on behalf of their domain. By creating an SPF record in the domain's DNS settings, domain owners can help prevent unauthorized users from sending emails that appear to come from their domain, which is a common tactic used in phishing and spam attacks.

When an email is received, the receiving mail server checks the SPF record of the sending domain to verify that the IP address of the mail server sending the email is included in the authorized list. If the sending server's IP is not included, the email may be flagged as suspicious or rejected altogether. This mechanism significantly enhances the integrity and security of email communication by helping to combat email spoofing.

The other options, such as assigning IP addresses and encrypting email traffic, do not directly relate to the core function of SPF. While validating incoming emails is a step that might occur in conjunction with other protocols, SPF specifically addresses the authorization of sending mail servers.