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 look as being sent from a different one, generally with the idea to scam the recipient someway. If SPF protection is activated for a domain name, a special record is generated for it in the Domain Name System and all of the DNS servers around the world get it. The record contains all of the email servers that are allowed to send authentic messages from an address part of the domain. When an e-mail is sent, the very first DNS server it encounters verifies the SPF record and when its sending server is permitted, the message is forwarded to the target receiver. When, however, the sending server doesn't exist in the SPF record for the specified domain, the email message will not be sent and it will be discarded. When you use this service, it'll prevent third parties from sending spam emails that look as if they have been sent by you.