DMARC in a Multi-Domain Environment: Best Practices for Complex Setups

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While handling single domains with DMARC is easy, DMARC in a multi-domain environment is also possible, though it may seem challenging.

Email is a standard cyberattack tool used by malicious actors, and attacks through email have significantly intensified as more business organizations migrate to the cloud environment. Hence, cybersecurity focuses on plugging the gaps and preventing malicious actors from exploiting the email route.

Statistics show that the most common cyberattack vectors threat actors use through email are phishing, spoofing, whaling, BEC, etc. DMARC is a recognized email authentication protocol that protects your domain from such cyberattack attempts. The following discussion shows configuring DMARC for multiple domains is as easy as for a single domain.

The Role of DMARC

DMARC (Domain-based Message Authentication, Reporting, and Conformance) is the ideal solution to protect email domains and prevent email phishing, spoofing, and fraud. DMARC verifies the sender’s ID and domain and instructs the recipient’s network servers on handling unauthenticated email messages.

While most DMARC users know how to handle individual domains using DMARC, many are unsure how to use DMARC to manage multiple domains. The below practical tips make it easy to manage the DMARC environment in a multiple-domain setup. 

Understanding DMARC for Email Protection

DMARC offers a comprehensive solution to the pressing issue of email security. It is designed to prevent unauthorized use of domains and protect against various cyberattack vectors, including phishing, spoofing, and business email compromise (BEC). By verifying the authenticity of email senders, DMARC enables organizations to ensure that incoming emails are legitimate and not forged by malicious actors.

While many DMARC users are familiar with how to handle the configuration for individual domains, the process becomes more complex when managing multiple domains. However, with the right approach and practical tips, managing DMARC for multiple domains can be as seamless as managing it for a single domain.

Select a DMARC Policy Level

Firstly, set up the DMARC configuration to manage multiple domains by choosing a policy level to suit your requirements. As most users know, DMARC has the following three policy levels:

• p=none
• p=quarantine
• p=reject

 Accordingly, the DMARC server takes the following actions respectively:

• Monitors but does not take any action
• Marks unauthenticated email messages and spam and moves them to a separate folder
• Rejects the email and returns it to the sender, respectively

You can choose your preferred level for each domain based on the requirements. It is advisable to start with ‘p=none’ and then graduate to ‘p=quarantine,’ followed by ‘p=reject’ once the email authentication and sending issues are adequately addressed.

Simplifying DMARC for Multiple Domains

One of the key steps in managing DMARC for multiple domains is to carefully select the appropriate policy level for each domain based on specific requirements. DMARC offers three policy levels: “p=none,” “p=quarantine,” and “p=reject.” Each policy level dictates the actions the DMARC server takes when it encounters unauthenticated emails.

Starting with “p=none” allows organizations to monitor email traffic without taking any action. Gradually, they can move to “p=quarantine,” marking unauthenticated emails as spam and moving them to a separate folder. Finally, when authentication and sending issues are addressed, organizations can implement “p=reject,” where unauthenticated emails are outright rejected and returned to the sender.

By adopting this step-by-step approach, organizations can carefully fine-tune their email authentication process and gradually enhance their email security while minimizing potential disruptions to legitimate email communication.

DMARC Configuration with SPF and DKIM

The next step is configuring SPF and DKIM for each domain and subdomain because DMARC configuration depends on these authentication methods. SPF approves the DNS record authorizing specific IP addresses to send emails on the domain’s behalf. And DKIM uses digital signatures to validate the email’s integrity and origin.

Therefore, your DMARC configuration involves creating and publishing SPF and DKIM records for all domains and subdomains. However, you must ensure they align with your DMARC policy.

Enhancing Email Security with DMARC Policies

To effectively implement DMARC for multiple domains, it is essential to configure SPF and DKIM for each domain and subdomain. SPF (Sender Policy Framework) allows organizations to authorize specific IP addresses to send emails on their domain’s behalf, while DKIM (DomainKeys Identified Mail) uses digital signatures to validate the integrity and origin of emails. These authentication methods play a crucial role in DMARC configuration and ensure that the DMARC policy aligns with the organization’s email authentication practices.

Once SPF and DKIM are set up and aligned with the DMARC policy, organizations must publish DMARC records for all domains and subdomains. These records define the DMARC policy itself, contact information, and reporting preferences. By creating and publishing DMARC records for each domain, organizations ensure a cohesive and consistent approach to email security, matching their SPF and DKIM records accurately.

Publishing DMARC Records for All Domains

Step 3 constitutes publishing DMARC records for each domain and subdomain. This record defines the DMARC policy, your contact information, and reporting preferences. Creating and publishing DMARC records for all domains ensures matching your SPF and DKIM records. It is best to use a DMARC generation template for creating your DMARC records which you can add to your DNS server.

Monitoring and Analyzing DMARC Reports

DMARC reports provide comprehensive information regarding the authentication results and the email traffic sources. Generally, two types of DMARC reports are generated for monitoring and analysis:

• Aggregate reports summarize the overall DMARC performance, the proportion and volume of authenticated/unauthenticated messages, and each sender’s IP address and domains.
• Forensic reports provide details of failed messages, including the email header, body, and failure reason. The DMARC analyzer tool on your dashboard can interpret these reports and identify issues for remediation.

Tweak Your DMARC Policy as Required

Tweaking your DMARC policy optimizes email security and deliverability while enhancing the DMARC server’s reputation. You can change the policy level, reporting frequency, alignment mode, or subdomain policy depending on your requirements. It allows you to whitelist or blacklist specific senders, IP addresses, and domains or delegate the DMARC policy to third-party services.

Educating Your Staff and Other Stakeholders

The final step in managing multiple domain setups is to educate your staff about the importance and utility of DMARC in managing cybersecurity threat vectors. Encouraging your customers, vendors, and clients to adopt robust DMARC policies and secure their network systems is also advisable.

Final Words

The procedure for enabling DMARC is the same for individual or multiple domains, with the only difference being that you repeat the same process with different domains. Though it may seem complicated or tedious, managing DMARC for multiple domains and subdomains is easy if you follow the tips carefully.