Security First, the importance and application of mail server SPF

The main function of SPF is to let the receiving mail server actively report the SPF record to the DNS server to which the sender belongs according to the sender's domain data. The receiving mail server then decides whether to accept or not according to the comparison result. This anti-spam mechanism is not restricted by SMTP SERVER, IMAP SERVER, POP3 SERVER.

Let's take an example: a fraudulent incident in news or newspapers mentions someone calling you to claim to be a bank and making money fraud. The middle means is nothing more than defrauding your trust with false lines. On the Internet, the same situation has been repeated: spam sources stealing someone else's email account to prevent letters from being returned to their real email address; fraud groups stealing other people's email accounts to avoid their own whereabouts; computer viruses or The worm wants to deliberately blur its source and randomly use any email account; hackers dress up as someone's friends to steal private secrets, and so on.

At this point, the SPF mechanism allows the sender to present his "good citizen card" on the envelope that is sent to tell the other party: "I am a good person!". The receiving end can be authenticated with the DNS server to which the sending end belongs. At the same time, the receiving end can also make a judgment on the response of the sender's DNS, is this email a spam?

How to build this mechanism? For most ADSL network solutions that SMEs use, ISPs usually only issue a fixed set of IP addresses to customers. Simply put, the SPF record requires only a short line to handle the network environment of most users, such as: [v=spf1 a mx ptr ~all].