DMARC Configuration Guide: Enhancing Email Deliverability

DMARC, which stands for Domain-based Message Authentication, Reporting, and Conformance, is an email authentication protocol that helps protect email domains from being used for email spoofing, phishing, and other malicious activities.

DMARC builds on the SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) protocols, providing additional layers of authentication and reporting.

Importance of DMARC

Email phishing attacks often involve using forged sender addresses, making distinguishing legitimate emails from malicious ones challenging.

DMARC addresses this issue by allowing domain owners to specify how their emails should be authenticated and what action should be taken if authentication fails. This helps organizations protect their brand and users from phishing attempts.

Key components of DMARC

1. DNS Records

   • SPF (Sender policy framework): Specifies the authorized mail servers for a domain. To configure, refer to more on this document.

   • DKIM (DomainKeys Identified Mail): Enables domain owners to sign their emails with a digital signature. To configure, refer to more on this document.

2. DMARC Record
   • Combines SPF and DKIM results and defines the domain’s DMARC policy.
   • Specifies whether to quarantine or reject emails that fail authentication.
   • Includes a reporting mechanism to get reports for feedback on the authentication issues.

Configuring DMARC

Create a DMARC TXT record in your DNS.

Example DMARC Record

_dmarc.example.com.   IN   TXT   "v=DMARC1; p=quarantine; rua=mailto:dmarc@example.com; ruf=mailto:dmarc@example.com"

• v=DMARC1: Indicates the use of DMARC version 1.
• rua: Specifies the email address to receive aggregate reports.
• ruf: Specifies the email address to receive forensic (failure) reports.
• p=quarantine: Specifies the DMARC policy, e.g., quarantine or reject.

Here are additional options for the “p=” parameter,

1. none: Indicates no action should be taken if the message fails authentication.
   This is often recommended during the initial implementation phase to monitor and analyze DMARC reports without impacting the delivery of emails.

   Example DMARC Record with “p=none”:

   _dmarc.example.com.   IN   TXT   "v=DMARC1; p=none; rua=mailto:dmarc@example.com; ruf=mailto:dmarc@example.com"
   

2. quarantine: Specifies that the email should be delivered to the recipient’s spam or quarantine folder.

   Example DMARC Record with “p=quarantine”:

   _dmarc.example.com.   IN   TXT   "v=DMARC1; p=quarantine; rua=mailto:dmarc@example.com; ruf=mailto:dmarc@example.com"
   

3. reject: Instructs the receiving mail server to reject the message outright.

   Example DMARC Record with “p=reject”:

   _dmarc.example.com.   IN   TXT   "v=DMARC1; p=reject; rua=mailto:dmarc@example.com; ruf=mailto:dmarc@example.com"
   

Recommendation

It’s advisable to start with “p=none” during the initial implementation. This allows you to collect and analyze DMARC reports without affecting the delivery of emails.

Once you are confident that legitimate emails are properly authenticated, you can gradually transition to a more restrictive policy, such as “p=quarantine” or “p=reject.”

Example DMARC Record with “p=none” for Initial Setup:

_dmarc.example.com.   IN   TXT   "v=DMARC1; p=none; rua=mailto:dmarc@example.com; ruf=mailto:dmarc@example.com"

Remember to regularly review DMARC reports and adjust the policy based on your analysis and evolving email authentication practices.

Monitor and analyze reports

Regularly review the DMARC reports to identify and address any authentication issues and adjust the DMARC policy if needed.

Conclusion

Implementing DMARC enhances email security by preventing unauthorized use of your domain.

To ensure a secure email environment, monitor the reports and update configurations based on feedback regularly.

Note: It is crucial to tailor SPF, DKIM, and DMARC records according to your specific email infrastructure and requirements. Additionally, always use secure methods to manage DNS records and store private keys.