Sender Policy Framework, or SPF, is a verification system, which is employed to prevent the so-called email spoofing where an email message can be sent from one e-mail address, but to appear as being sent from another, often with the purpose to fraud the recipient someway. When SPF protection is enabled for a domain, a special record is generated for it in the Domain Name System and all DNS servers around the world have it. The record includes all the mail servers that are allowed to send legitimate messages from an email address part of the domain. When an e-mail is sent, the first DNS server it encounters verifies the SPF record and if the sending server is permitted, the message is sent to the targeted destination. If, however, the sending server is not contained in the SPF record for the specified domain, the email message won't be sent and it will be removed. In the event that you employ this solution, it'll prevent third parties from sending spam messages that appear to have been sent from you.