Sender Policy Framework, or SPF, is a validation system, which is intended to prevent the so-called e-mail spoofing where an email message can be sent from one email address, but to look as being sent from another, often with the purpose to scam the recipient for some reason. When SPF protection is activated for a domain, an exclusive record is made for it in the Domain Name System and all DNS servers around the world have it. The record includes all of the email servers that are permitted to send authentic messages from an email address within the domain. When a message is sent, the very first DNS server it goes to verifies the SPF record and when its sending server is authorized, the message is sent to the targeted receiver. When, however, the sending server is not included in the SPF record for the specified domain, the e-mail message won't be sent and it will be removed. In case you employ this service, it'll stop third parties from sending spam e-mails that seem to have been sent by you.