Sender Policy Framework, or SPF, is a validation system, which is employed to stop the so-called email spoofing where an e-mail message is sent from one email address, but to look as being sent from another one, typically with the objective to scam the recipient in some way. When SPF protection is activated for a domain name, an exclusive record is created for it in the Domain Name System and all the DNS servers globally get it. The record features all of the mail servers that are permitted to send legitimate messages from an e-mail address within the domain. When an email is sent, the first DNS server it goes to verifies the SPF record and if the sending server is permitted, the message is forwarded to the target receiver. When, however, the sending server doesn't exist in the SPF record for the given domain, the e-mail message won't be forwarded and it'll be removed. In case you employ this service, it'll prevent third parties from sending spam emails that seem to have been sent by you.