DMARC Record Best Practices:
How To Strengthen Your Email Security

The importance of email security is at an all-time high. As cyberattacks grow more advanced, it is essential for organizations to strengthen their email systems against dangers such as phishing, spoofing, and impersonation. A key resource available to you is DMARC (Domain-based Message Authentication, Reporting & Conformance). When implemented effectively, DMARC not only secures your domain but also enhances the trustworthiness of your brand among customers and partners.


What is DMARC and Why It Matters


DMARC is a protocol designed for email authentication that enhances two pre-existing systems: SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail). It allows domain owners to establish guidelines for how email recipients should manage messages that are deemed unauthorized. Additionally, DMARC includes reporting capabilities that assist organizations in overseeing and refining their email authentication methods.

In the absence of DMARC, cybercriminals can impersonate your domain to distribute deceptive emails, harming your reputation and possibly resulting in financial repercussions. Discover more by clicking this source.



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Best Practices for Implementing DMARC Records


1. Start with Monitoring Mode (p=none)

When you initially implement DMARC, it's advisable to start with a policy that only monitors (p=none). This strategy enables you to gather essential information without affecting the delivery of your emails. You will obtain DMARC reports that reveal details about who is sending emails on behalf of your domain and the authentication status of those messages.

Important advice: Consistently examine these reports to gain insights into the authentic sources of emails for your domain and to detect any unauthorized activities.


2. Gradually Enforce Stronger Policies

After gathering enough data and ensuring that authentic email sources are correctly verified, you can implement more stringent DMARC policies:

  • Quarantine (p=quarantine): Emails deemed suspicious will be directed to the recipients' spam or junk folders.

  • Reject (p=reject): Emails that do not pass DMARC verification will be entirely blocked.

  • Recommended approach: Gradually implement changes and conduct thorough testing at every phase to prevent unintentional interruptions to legitimate email communications.


3. Align SPF and DKIM with Your Domain

To ensure DMARC functions properly, either SPF or DKIM (ideally both) must be properly aligned with your domain:

  • For SPF alignment: The domain in the "Return-Path" (envelope sender) should correspond to the domain in the "From" field.

  • For DKIM alignment: The domain specified in the "d=" tag of the DKIM signature must be the same as the "From" domain.

A frequent cause of DMARC failures is misalignment. Make sure that all legitimate email sources have correctly set up SPF and DKIM to align with your domain.


4. Use Subdomain Policies

Cybercriminals frequently exploit subdomains when the main domain has security measures in place, but the subdomains do not. To safeguard your subdomains, utilize DMARC's sp tag to enforce specific policies.

For instance:

sp=reject; - This configuration guarantees that every subdomain associated with your primary domain is secured by the "reject" policy.

Insider Tip: It’s essential to set clear policies for subdomains rather than relying on the assumption that the policy of the main domain will automatically extend to them.


Optimizing DMARC Reports for Better Insight


1. Set Up Aggregate and Forensic Reporting

DMARC provides two categories of reports:

  • Aggregate reports (RUA): These offer a summary of overall DMARC performance.

  • Forensic reports (RUF): These deliver in-depth details regarding specific instances of authentication failures.

To enhance your insight into email operations, ensure you set up both RUA and RUF email addresses in your DMARC configuration.

For instance:

rua=mailto:dmarc-aggregate@yourdomain.com; ruf=mailto:dmarc-forensics@yourdomain.com;



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2. Monitor Reports Consistently

Gathering DMARC reports is only beneficial if you actively keep track of them. Establish a routine for evaluating these reports, which can be done through manual checks, automated tools, or external DMARC monitoring services.

Key Point: Pay attention to patterns such as abrupt increases in unauthenticated traffic, the emergence of unfamiliar sources, or fluctuations in pass/fail rates, as these may signal emerging threats or configuration problems.


Common Pitfalls to Avoid


  • Overlooking third-party service authentication: It's crucial to properly authenticate services such as Customer Relationship Managements, marketing tools, and helpdesk applications that send emails for you.

  • Ignoring DNS record updates: Make it a habit to check and revise your SPF, DKIM, and DMARC records to align with any modifications in your email system.

  • Rushing into a “reject” policy: Implementing a strict policy without adequate oversight can lead to the blockage of legitimate emails.