Understanding SPF, DKIM, and DMARC: The Guardians of Email Security

In the digital age, email has become a primary communication tool, both in our personal and professional lives. However, this popularity also makes it a prime target for spammers and phishers. To combat this, three main email authentication standards have been developed: SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting & Conformance). Let’s dive into what each of these standards means and how they contribute to email security.

SPF (Sender Policy Framework)

SPF is an email authentication technique that helps in verifying the sender's identity. This is done by checking the sender's IP address against the list of IP addresses authorized by the domain's administrators. In simple terms, SPF allows a domain to declare which mail servers are permitted to send emails on its behalf.

How it works:

• A domain administrator publishes the policy in the DNS records.

• When an email is sent, the receiving server checks these records to verify if the email comes from an authorized server.

• If the check passes, the email is considered legitimate. If not, it can be flagged or rejected.

DKIM (DomainKeys Identified Mail)

DKIM takes authentication a step further by adding a digital signature to the email. This signature is attached to the email’s header and is verified using a public cryptographic key published in the domain's DNS records.

How it works:

• The sending server attaches a unique DKIM signature to the header of each outgoing email.

• The receiving server then uses the public key listed in the sender's DNS records to decrypt the signature.

• If the decrypted signature matches the content of the email, it proves that the email has not been tampered with after it was sent and that it indeed comes from the claimed domain.

DMARC (Domain-based Message Authentication, Reporting & Conformance)

DMARC is a protocol that uses SPF and DKIM to determine the authenticity of an email message. It enables domain owners to publish policies in their DNS records that define how receiving email servers should handle messages that don’t pass SPF and DKIM checks.

How it works:

• DMARC inspects both SPF and DKIM authentication results.

• Based on the domain's DMARC policy, the email will either be delivered, quarantined, or rejected if it fails the checks.

• DMARC also provides reporting capabilities, so domain owners can get feedback on emails being sent from their domain.

By MaximiseMedia