Sender Policy Framework, or SPF, is a validation system, that is used to stop the so-called email spoofing where an email message can be sent from one e-mail address, but to seem as being sent from a different, frequently with the objective to scam the recipient in some way. If SPF protection is enabled for a domain name, a unique record is generated for it in the Domain Name System and all of the DNS servers around the world get it. The record features all of the mail servers that are allowed to send legitimate messages from an email address within the domain. When a message is sent, the very first DNS server it encounters checks the SPF record and when the sending server is authorized, the message is sent to the target receiver. When, however, the sending server is not present in the SPF record for the particular domain, the e-mail message will not be sent and it'll be removed. In case you employ this solution, it will prevent third parties from sending spam messages that appear to have been sent by you.