Sender Policy Framework (SPF)

What is it?

What is it?

The "Sender Policy Framework (SPF)" is an email authentication protocol used to prevent email spoofing and unauthorized use of domain names in email messages. SPF allows domain owners to specify which mail servers are authorized to send emails on behalf of their domains, helping to detect and block forged or fraudulent emails and enhance email security and deliverability.

Key points to remember

Key points to remember

  • Authentication Mechanism: SPF uses DNS records to publish a list of authorized mail servers for a domain, indicating to receiving email servers which sources are permitted to send emails using the domain name.

  • Domain Ownership Verification: By authenticating the origin of email messages, SPF helps verify the legitimacy of sender domains and prevents domain spoofing, impersonation, or phishing attacks.


  • Mechanism Types: SPF records can include mechanisms such as "include," "a," "mx," and "ip4/ip6" to specify authorized sources, allowing domain owners to designate specific mail servers, IP addresses, or domains as legitimate senders.


  • Soft Fail vs. Hard Fail: SPF evaluation results in either a "soft fail" (neutral or non-compliant) or "hard fail" (failed authentication) outcome, indicating the level of strictness in handling unauthorized emails, such as marking them as spam or rejecting them outright.


  • Interoperability: SPF works with other email authentication mechanisms, such as DKIM and DMARC, to protect against fraud, spoofing, and abuse, improving email deliverability and trustworthiness.

Example of Use

Example of Use

  1. Domain Authentication: An organization publishes an SPF record in its DNS settings to specify the authorized mail servers permitted to send emails using its domain name, preventing unauthorized use of the domain for phishing or spamming purposes.


  2. Email Filtering: Receiving email servers use SPF authentication results as part of their spam filtering and email security measures to verify the legitimacy of incoming emails and assess their trustworthiness, helping to reduce the risk of spam, spoofing, and phishing attacks.

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