An Essential Sender Policy Framework (SPF) Guide For You

  • With the rise in phishing emails from malicious senders, SPF becomes essential than ever.
  • It is an email-validation system that is devised to detect email spoofing.

Email addresses can easily be spoofed. It has become one of the most lucrative methods to trap the target and steal sensitive data or money without their knowledge. In some cases, these phishing emails are used to distribute information-stealing malware.

With the rise in phishing emails from malicious senders, SPF becomes essential than ever.

What is SPF?

It is a simple email-validation system that is devised to detect email spoofing. SPF or Sender Policy Framework provides a mechanism to allow receiving mail exchangers to verify if the incoming mail arrives from a genuine domain and from a host that is authorized by that domain administrator.

What are the other features?

It is an open standard that specifies a technical method to combat the forgery of the sender address. The present versions of SPF are SPFv1 also known as SPF Classic. It provides protection to the envelope sender address — used for the delivery of messages. Even more precisely, SPFv1 allows the owner of a domain to specify their mail sending policy, e.g. which mail servers they use to send mail from their domain.

What is an SPF Record?

It is a record that is used to communicate to mail exchanges that hosts are authorized to send mail for a domain. It is defined in RFC 4408 and clarified by RFC 7208. The SPF records are defined in a specific format — using TXT record type. In addition, there is also an SPF record Type which is used. However, it is deprecated and thus users should always have at least the TXT record definition present.

What is the mechanism of SPF?

There are several parameters that define what IP addresses are allowed to send email from the domain. The parameters include - a, mx, ip4, ip6, and Exists.

The IP addresses defined in the mechanisms will help a mail server compare them against the IP address of the sender.