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SPF (Sender Policy Framework)
What is SPF?
Email authentication protocols are in place to ensure the authenticity of emails being sent or received. SPF, or Sender Policy Framework, is one of the main email authentication protocols used today.
SPF allows domain owners to list which email servers have authorization to send emails using the domain. It is added as a DNS (Domain Name System) record by the domain owner.
Example SPF record
v=spf1 ip4:192.0.2.0/24 include:example.com -all
What is the purpose of SPF?
By listing the servers/IP addresses allowed to send emails from the domain, SPF helps the receiving server verify if the incoming email has originated from an authentic or approved source. This can prevent email attacks like spoofing and phishing.
How does SPF work?
- A domain publishes an SPF record in its DNS (Domain Name System) settings.
- This record lists IP addresses or hostnames permitted to send emails from that domain.
- When an email is received, the recipient's mail server checks the SPF record to see if the sender is authorized.
- One of the following results can be returned:
- Pass: The IP is authorized.
- Fail: The IP is not authorized.
- Soft fail: The IP is probably unauthorized but not definitively blocked.
- Neutral: No policy is defined.
Based on the result of the SPF check, the email is delivered, rejected, or quarantined.