How do SPF, DKIM, and DMARC Work Together?

Spam email messages have been a scourge since the Internet’s inception, and they’ve only gotten worse as the number of connected devices and people using the Internet has increased. Despite several efforts to develop anti-spam tools, a significant number of unwanted messages are still sent every day.

Fortunately, it seems like things are changing recently, with the widespread adoption of three relatively new tools: SPF, DKIM, and DMARC. Let’s have a quick look at each of these tools and what they achieve.

What are SPF, DKIM, and DMARC?

SPF (Sender Policy Framework) is a DNS text entry that displays a list of servers that are authorized to send mail for a particular domain. Since the owners/administrators are the only ones permitted to add/change the main domain field, the fact that SPF is a DNS entry can also be considered a way to enforce the fact that the list is authoritative for the domain.

DKIM (DomainKeys Identified Mail) can be thought of as a way to ensure that the messages’ content is authentic, that is, that it hasn’t been updated since they left the original mail server. The introduction of the traditional public/private key signing protocol adds an extra layer of trustability. 

The domain’s owners add a DNS entry with the public DKIM key, which receivers can use to verify that the message’s DKIM signature is right, while the server will sign the entitled mail messages with the corresponding private key on the sender side.

DMARC (Domain-based Message Authentication, Reporting, and Conformance) empowers SPF and DKIM by stating a simple policy for each of the aforementioned tools and allowing to set an address to submit information about the mail message statistics gathered by receivers against a particular domain.

How do they work?

All these tools rely heavily on DNS after the setup phase is finished, as explained below:

SPF

The receiving mail server retrieves the HELO message and the sender address upon receipt. The receiving mail server then performs a TXT DNS query against the alleged domain SPF entry. The SPF entry data is then used to validate the sender server. If the search fails, the sender server receives a rejection message.

DKIM

When sending an outgoing message, the domain infrastructure’s last server checks its internal settings to see if the domain used in the “From:” header is in its “signing table.” If the procedure does not end here, a new header named “DKIM-Signature” is applied to the mail message by using the private part of the key on the message content. 

The main content of the message cannot be changed from here on because the DKIM header will no longer fit. Upon receipt, the receiving server will perform a TXT DNS query to retrieve the key used in the DKIM-Signature sector. The DKIM header check result can then be used for deciding if a message is fraudulent or trustworthy.

DMARC

Upon receipt, the receiving mail server checks the DMARC record for any current DMARC policies and/or DKIM checks in the domain used by the SPF.

If either or both of the SPF and DKIM checks pass while remaining consistent with the DMARC policy, the check is considered successful; otherwise, if the DMARC check fails, based on the action published by the DMARC policy, it is marked as failed. If the check fails, based on the action published by the DMARC policy, different actions are taken.

Where Should You Start With Email Authentication?

The first move is to chat with your email support team on how to ensure that your emails are authenticated. 

We strongly advise using SPF, DKIM, and DMARC authentication for your messages, regardless of how you go about it. You’ll be able to acronym like the best of them while maintaining the safety and security of your brand’s reputation.

In Conclusion

ProDMARC assists you in ensuring DMARC implementation with both the company and third-party vendors. ProDMARC, as a product built on a mission to achieve safe and spoofing-free email networks across the entire internet room, allows DMARC reporting, providing volumes and patterns of outbound mails, including phishing campaigns, and yields proof for outbound mails’ reliability in terms of SPF, DKIM, and DMARC compliance. Get Started with top-class cybersecurity solutions for your business at ProgIST. Get in touch with us for the best cybersecurity solutions.