Sender Policy Framework, or SPF, is a verification system, that is employed to prevent the so-called email spoofing where an email message can be sent from one email, but to seem as being sent from another, often with the purpose to scam the recipient for some reason. If SPF protection is enabled for a domain name, a special record is generated for it in the Domain Name System and all of the DNS servers worldwide get it. The record contains all of the mail servers that are allowed to send authentic messages from an email address within the domain. When an email is sent, the first DNS server it encounters 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 given domain, the e-mail message will not be sent and it'll be discarded. When you use this service, it'll prevent third parties from sending spam e-mails which look as if they have been sent from you.