Sender Policy Framework, or SPF, is a verification system, which is used to stop the so-called e-mail spoofing where an e-mail message can be sent from one address, but to look as being sent from a different, often with the purpose to scam the recipient in some way. If SPF protection is activated for a domain, a unique record is created for it in the Domain Name System and all DNS servers worldwide get it. The record features all of the mail servers that are allowed to send legitimate messages from an email address under the domain. When a message is sent, the very first DNS server it goes to checks the SPF record and if its sending server is permitted, the message is sent to the target receiver. In case, however, the sending server doesn't exist in the SPF record for the particular domain, the e-mail message will not be sent and it'll be discarded. If you employ this solution, it will stop third parties from sending spam emails that look as if they have been sent by you.