What is SPF?

SPF stands for Sender Policy Framework, is an email authentication standard developed by AOL, in which domain of an e-mail sender can be authenticated for that sender. SPF compares the email sender’s actual IP address to a list of IP addresses authorized to send mail from that domain. thereby discouraging spam mailers, who routinely disguise the origin of their e-mail, a bad practice known as spoofing

The IP list is published in the domain’s DNS record.