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What is SPF?

What is SPF?

Sender policy framework (SPF) is an email authentication method that helps identify the mail servers allowed to send email for a given domain. Using SPF, internet service providers (ISPs) can identify emails from spoofers, scammers, and phishers as they try to send malicious emails from a domain belonging to a company or brand.


How does SPF work?

Generally, SPF establishes a policy called an SPF record that outlines which mail servers are authorized to send email from a domain. When an inbound server receives incoming mail, it references the rules for the bounce domain in the DNS and compares the IP address of the incoming mail to the authorized addresses defined in the SPF record. The receiving server then uses SPF record rules to determine if the incoming message will be accepted, rejected, or flagged.

Read also: What is an SPF record and why you need it 


Importance of SPF

A sender policy framework provides users with an additional layer of cybersecurity. It enables domain owners to create a list of approved inbound domains to minimize the risk of receiving malicious emails. It helps other servers verify your domain's legitimacy.

Without an SPF record, malicious actors can spoof your domain and networks, harm your reputation, and carry out cyberattacks that result in financial loss. Furthermore, if you don’t have an SPF, servers that receive your emails may flag or reject them because they can't determine the authenticity of your domain.

Go deeper: 

What is spoofing?

Cyberattacks on the healthcare sector 


The limits of SPF

While the sender policy framework offers some protection against spam and spoofing, it is not a complete email security solution. A forwarded email will evade an SPF test, and the SPF protocol can only spot email that spoofs the "from" address – the address that's visible to users.

Additionally, for SPF to work, organizations must keep their SPF records constantly updated – a time-consuming and cumbersome task that gets harder as companies change ISP providers.



DMARC, or domain-based message authentication, improves the sender policy framework protocol and the DKIM protocol. It prevents spoofing more successfully by requiring that the information in the "from" address align with other information about the sender. DMARC also requires that a message be authenticated with either SPF, DKIM, or both. It also improves reporting and details how messages that fail authentication should be handled.

See also: HIPAA Compliant Email: The Definitive Guide  



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