Understanding DMARC: A Guide for Organisations

In today’s digital age, email remains a critical communication tool for businesses. However, it is also a prime target for cyberattacks such as phishing and email spoofing. To combat these threats, organisations can implement DMARC (Domain-based Message Authentication, Reporting, and Conformance). This blog will explore what DMARC is and what steps organisations need to take to comply with this important email security protocol. 

What is DMARC?

DMARC is an email authentication protocol designed to give domain owners the ability to protect their domain from unauthorized use, commonly known as email spoofing. It builds on two existing mechanisms: Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM). By using DMARC, organisations can specify how the email receivers should handle messages that fail SPF or DKIM checks; this prevents fraudulent emails from reaching their intended recipients. 

How does it work?

DMARC aligns the domain in the email’s “From” field with the domains used in SPF and DKIM checks. If the alignment fails, the email can be rejected, quarantined, or allowed through based on the policy set by the domain owner. Additionally, DMARC provides a reporting mechanism that allows domain owners to receive feedback on emails that pass or fail DMARC checks. 

Why do you need it? 

From March 2025, DMARC will be mandatory in PCI Data Security Standards version 4.0. DMARC, recommended by the PCI SSC as a future-dated requirement as it protects companies from email-based attacks like phishing. After the deadline, companies processing card data must implement DMARC for robust email authentication. 

Steps to comply with DMARC

1. Implement SPF and DKIM: Before setting up DMARC, ensure that your domain has SPF and DKIM records configured. SPF specifies which IP addresses are allowed to send an email on behalf of your domain, while DKIM adds a digital signature to your emails. 

1. Publish a DMARC Record: Create a DMARC record and publish it in your DNS. This record will define your DMARC policy, including how to handle emails that fail authentication checks and where to send reports. 

1. Monitor and analyse reports: Use the reports generated by DMARC to monitor your email traffic. These reports will help you identify any unauthorised use of your domain and adjust your policies as needed. 

1. Gradually enforce policies: Start with a “none” policy to monitor your email traffic without affecting delivery. Once you are confident that your legitimate emails are passing DMARC checks, you can move to a “quarantine” or “reject” policy to block fraudulent emails. 

1. Regularly review and update: Continuously review your DMARC reports and update your SPF, DKIM, and DMARC records as necessary to adapt to changes in your email infrastructure and threat landscape. 

Benefits

Implementing DMARC offers several benefits: 

• Enhanced Security: Protects your domain from being used in phishing and spoofing attacks. 

• Improved Email Deliverability: Helps ensure that legitimate emails reach their intended recipients. 

• Brand Protection: Prevents unauthorised use of your domain, safeguarding your brand’s reputation. 

By following these steps, organisations can effectively implement DMARC and enhance their email security posture. As cyber threats continue to evolve, staying ahead with robust email authentication protocols like DMARC is essential for protecting your business and maintaining trust with your customers. 

Grey Matter – cyber security licensing experts 

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