The Sender Policy Framework (SPF) is a method used to detect and prevent email spoofing, which is when attackers send emails that appear to be from a legitimate domain, but are actually sent from a different domain. SPF works by allowing the owner of a domain to specify which mail servers are authorized to send email on behalf of their domain.
When an email is received by a mail server, the server can check the SPF record for the domain that the email claims to be sent from. The SPF record is a DNS record that specifies which servers are authorized to send email for that domain. If the server that sent the email is not included in the SPF record, the email can be marked as spam or rejected.
To use SPF, the domain owner must publish an SPF record in the domain's DNS records. This record specifies which servers are authorized to send email on behalf of the domain. When an email is received, the recipient's mail server can check the SPF record to see if the server that sent the email is listed as an authorized sender. If the server is not listed, the email may be marked as spam or rejected.
In summary, SPF is a way for email recipients to verify that an email was actually sent by a server that is authorized to send email on behalf of the domain it claims to be sent from. It helps to protect against email spoofing by allowing the recipient to check that the email was not sent from an unauthorized server.