Sender Policy Framework, or SPF, is a verification system, which is used to stop the so-called email spoofing where an email message can be sent from one email, but to appear as being sent from another, often with the purpose to scam the recipient in some way. When SPF protection is activated for a domain, a specific record is generated for it in the Domain Name System and all DNS servers around the world get it. The record contains all of the e-mail servers that are allowed to send legitimate messages from an email address part of the domain. When a message is sent, the first DNS server it goes to checks the SPF record and when its sending server is permitted, the message is sent to the targeted receiver. In case, however, the sending server is not included in the SPF record for the particular domain, the email message won't be submitted and it'll be removed. Whenever you employ this service, it'll stop third parties from sending spam e-mails which seem to have been sent from you.