Sender Policy Framework, or SPF, is a verification system, which is intended to prevent the so-called email spoofing where an email message can be sent from one email address, but to appear as being sent from another, frequently with the idea to fraud the recipient for some reason. If SPF protection is enabled for a domain, a unique 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 address within the domain. When a message is sent, the very first DNS server it goes to checks the SPF record and if the sending server is permitted, the message is forwarded to the target destination. In case, 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 discarded. If you employ this service, it will stop third parties from sending spam e-mails that appear to have been sent from you.