Sender Policy Framework, or SPF, is a validation system, which is intended to stop the so-called e-mail spoofing where an email message is sent from one email address, but to appear as being sent from another, typically with the purpose to scam the recipient for some reason. When SPF protection is activated for a domain name, a unique record is generated for it in the Domain Name System and all DNS servers globally get it. The record contains all the mail servers that are allowed to send authentic messages from an email address within the domain. When an e-mail is sent, the very first DNS server it goes to checks the SPF record and if its sending server is permitted, the message is sent to the target receiver. In case, however, the sending server is not contained in the SPF record for the particular domain, the email message won't be forwarded and it'll be removed. In case you employ this service, it will stop third parties from sending spam emails which look as if they have been sent by you.