Sender Policy Framework, or SPF, is a validation system, which is intended to prevent the so-called email spoofing where an e-mail message is sent from one e-mail, but to look as being sent from another one, ordinarily with the idea to scam the recipient in some way. When SPF protection is activated for a domain, an exclusive record is generated for it in the Domain Name System and all of the DNS servers worldwide receive it. The record contains all mail servers that are allowed to send authentic messages from an e-mail address under the domain. When an email is sent, the very first DNS server it goes to verifies the SPF record and if its sending server is permitted, the message is sent to the targeted receiver. In case, however, the sending server is not present in the SPF record for the given domain, the message won't be submitted and it will be removed. When you use this service, it'll prevent third parties from sending spam which look as if they have been sent by you.