Sender Policy Framework, or SPF, is a validation system, which is used to prevent the so-called email spoofing where an email message can be sent from one email, but to seem as being sent from a different one, generally with the objective to scam the recipient someway. When SPF protection is enabled for a domain name, a specific record is made for it in the Domain Name System and all DNS servers around the world get it. The record features all mail servers that are allowed to send legitimate messages from an email address under the domain. When an e-mail is sent, the first DNS server it goes to verifies the SPF record and if its sending server is authorized, the message is sent to the targeted destination. When, however, the sending server is not contained in the SPF record for the particular domain, the email message will not be submitted and it will be discarded. In case you employ this solution, it'll stop third parties from sending spam e-mails which seem to have been sent by you.