Sender Policy Framework, or SPF, is a validation system, which is used to prevent the so-called e-mail spoofing where an email message is sent from one address, but to seem as being sent from another one, often with the objective to scam the recipient someway. When SPF protection is activated for a domain name, a unique record is made for it in the Domain Name System and all of the DNS servers globally get it. The record contains all e-mail servers that are permitted to send legitimate messages from an e-mail address within the domain. When a message is sent, the very first DNS server it goes to verifies the SPF record and in case its sending server is permitted, the message is forwarded to the targeted receiver. In case, however, the sending server is not contained in the SPF record for the specified domain, the email message will not be forwarded and it will be discarded. In the event that you use this service, it will prevent third parties from sending spam e-mails which look as if they have been sent from you.