Sender Policy Framework, or SPF, is a validation system, that is designed to stop the so-called e-mail spoofing where an email message can be sent from one email address, but to look as being sent from a different, often with the idea to fraud the recipient someway. When SPF protection is activated for a domain, an exclusive record is created for it in the Domain Name System and all DNS servers globally get it. The record contains all email servers that are permitted to send legitimate messages from an email address within the domain. When an e-mail is sent, the very first DNS server it goes to verifies the SPF record and when the sending server is permitted, the message is sent to the targeted receiver. If, however, the sending server is not contained in the SPF record for the given domain, the e-mail message will not be submitted and it will be discarded. Whenever you use this service, it'll stop third parties from sending spam e-mails that look as if they have been sent from you.