Authentication, Reporting, and Conformance (ARC): Bridging the Email Authentication Gap

Shivendra Pratap Singh


High Court Lucknow


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Authentication, Reporting, and Conformance (ARC): In an age where cyber threats are ever-evolving, email remains one of the primary channels for communication, but it also remains a significant vector for cyberattacks. The evolution of email security has brought forward several protocols aimed at ensuring sender authenticity and message integrity. One such advanced method in the arsenal of email security is the Authentication, Reporting, and Conformance (ARC) protocol. Let’s dive into the depths of ARC, exploring its function, significance, and how it complements other email security mechanisms.

1. Understanding Authentication, Reporting, and Conformance (ARC)

ARC is designed to preserve email authentication results when emails undergo subsequent intermediary handling, such as forwarding or mailing list processing. In simpler terms, while some protocols focus on verifying the original sender’s authenticity, ARC ensures that authentication results remain intact even when the email passes through various mail servers or services.

2. Why ARC? The Challenge with Email Forwarding

Traditional authentication mechanisms like SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) often break when an email is forwarded. This is because:

  • SPF: Validates that the sending server is authorized to send on behalf of a domain. Forwarding can alter this, causing SPF to fail.
  • DKIM: Ensures message integrity. Forwarding or modifications by mailing lists can change the message content, causing DKIM checks to fail.

When these authentication methods fail, the forwarded emails might be deemed suspicious or fraudulent, leading to delivery issues.

3. How ARC Works

ARC operates by preserving the original authentication results and adding its own signature every time an email undergoes changes, like when forwarded:

  • Authentication: ARC retains the initial SPF, DKIM, and DMARC (Domain-based Message Authentication, Reporting, and Conformance) results, even when the email is modified or forwarded.
  • Reporting: Provides a history of the email’s journey, including all intermediaries it passed through.
  • Conformance: Ensures that DMARC policies are applied correctly, based on the preserved authentication results.

4. Benefits of Implementing ARC

a. Improved Email Delivery:

ARC ensures that legitimate forwarded emails or emails passed through mailing lists are not mistakenly flagged as suspicious.

b. Enhanced Visibility:

With ARC’s reporting, administrators can track an email’s journey, providing clarity on why certain authentication results were obtained.

c. Compatibility:

ARC complements existing email security protocols, ensuring that they function effectively in various email handling scenarios.

5. Implementing ARC

For domain owners or email service providers:

  • a. Configuration: Start by setting up ARC on your mail servers. Depending on the server software, this may require specific modules or plugins.
  • b. Testing: Like all email security mechanisms, it’s crucial to test ARC in varied scenarios, ensuring it functions as expected.
  • c. Monitor: Regularly review ARC reports to maintain an understanding of email flow and any potential issues.

6. Considerations with ARC

  • It’s Not a Replacement: ARC doesn’t replace SPF, DKIM, or DMARC. Instead, it acts as a supplement, ensuring their effectiveness in more complex email scenarios.
  • Adoption Rate: For ARC to be truly effective, it requires widespread adoption by email service providers and receivers.


ARC is an innovative step in ensuring email authentication’s robustness in the modern, complex email ecosystem. By preserving the results of initial authentication checks and offering insights into email routing, it fills a critical gap left by traditional email authentication methods. For businesses and domain owners, understanding and implementing ARC can mean the difference between essential communications reaching their destination or being wrongly flagged. In the vast landscape of email security, ARC stands as a testament to the industry’s commitment to adapting and evolving in the face of new challenges.