Sender Policy Framework, or SPF, is a verification system, which is designed to stop the so-called e-mail spoofing where an email message can be sent from one e-mail, but to look as being sent from a different, often with the idea to fraud the recipient for some reason. If SPF protection is enabled for a domain name, a specific record is generated for it in the Domain Name System and all the DNS servers worldwide get it. The record features all mail servers that are allowed to send legitimate messages from an e-mail address under the domain. When a message is sent, the first DNS server it goes to checks the SPF record and in case the sending server is permitted, the message is forwarded to the target receiver. In case, however, the sending server is not contained in the SPF record for the given domain, the message will not be submitted and it will be discarded. In case you employ this solution, it will prevent third parties from sending spam that seem to have been sent from you.