Sender Policy Framework, or SPF, is a validation system, that is intended to stop the so-called e-mail spoofing where an e-mail message is sent from one e-mail address, but to look as being sent from a different, ordinarily with the purpose to scam the recipient in some way. When SPF protection is enabled for a domain name, an exclusive record is generated for it in the Domain Name System and all of the DNS servers around the world get it. The record contains all mail servers that are permitted to send legitimate messages from an address within the domain. When an email is sent, the very first DNS server it encounters checks the SPF record and in case its sending server is authorized, the message is sent to the targeted receiver. When, however, the sending server doesn't exist in the SPF record for the given domain, the message will not be sent and it'll be removed. If you employ this solution, it will prevent third parties from sending spam emails which look as if they have been sent by you.