Sender Policy Framework, or SPF, is a validation system, which is used to prevent the so-called email spoofing where an e-mail message can be sent from one address, but to seem as being sent from another, often with the purpose to fraud the recipient in some way. If SPF protection is enabled for a domain name, a unique record is made for it in the Domain Name System and all of the DNS servers globally have it. The record includes all the email servers that are allowed to send valid messages from an address within the domain. When an e-mail is sent, the first DNS server it encounters verifies the SPF record and if the sending server is authorized, the message is sent to the targeted destination. If, however, the sending server is not present in the SPF record for the given domain, the e-mail message won't be forwarded and it will be removed. In case you use this solution, it will prevent third parties from sending spam emails which look as if they have been sent from you.