Sender Policy Framework, or SPF, is a validation system, which is intended to prevent the so-called email spoofing where an email message is sent from one e-mail, but to seem as being sent from another, typically with the idea to scam the recipient for some reason. If SPF protection is activated for a domain, a special record is made for it in the Domain Name System and all the DNS servers globally get it. The record includes all mail servers that are allowed to send legitimate messages from an email address part of the domain. When a message is sent, the very first DNS server it encounters checks the SPF record and if the sending server is permitted, the message is forwarded to the targeted destination. When, however, the sending server doesn't exist in the SPF record for the specified domain, the e-mail message won't be submitted and it will be removed. In the event that you employ this service, it'll prevent third parties from sending spam messages which look as if they have been sent from you.