What is ARC and how does it affect the trustworthiness of emails?

Email communication is still one of the main ways people and organizations share information. However, with the growth of phishing and spoofing, email security has become a key concern. Standards such as SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail) and DMARC (Domain-based Message Authentication, Reporting & Conformance) help protect email communications. However, these standards can fail when email is forwarded across different servers. ARC (Authenticated Received Chain) comes as a solution to solve this problem.

What is ARC?

ARC (Authenticated Received Chain) is an email authentication system designed to maintain the trustworthiness of emails that pass through different forwarding servers. This protocol helps recipients verify that the email has not been altered or tampered with during transmission through multiple servers, ensuring that the original authentication information remains intact.

How does ARC work?

ARC adds special headers to email messages that allow you to track and authenticate each step of the email journey across multiple servers. This header contains three main components:

1. ARC-Authentication-Results (AAR): This header contains the results of the authentication checks (SPF, DKIM, DMARC) performed by the forwarding server.
2. ARC-Message-Signature (AMS): This header contains a digital signature that verifies that the contents of the email and its authentication results have not been altered during transmission.
3. ARC-Seal (AS): This header contains a signature that confirms the authenticity and integrity of ARC headers added by forwarding servers.

Each server that forwards the email adds its own set of these three headers, allowing the final receiving server to verify the entire forwarding chain.

Why is ARC important?

1. Preserving Authentication Results: When forwarding email across different servers, the authentication protocols (SPF, DKIM, DMARC) may fail because the forwarding servers may change the content of the email or its headers. ARC ensures that these authentication results are preserved and can be verified at the end of the chain.
2. Spoofing Protection: ARC helps recipients verify that the email has not been altered or spoofed as it travels through different servers, reducing the risk of spoofing.
3. Improves deliverability: Emails that pass authentication checks and are verified by ARC are more likely to be delivered to the recipient's inbox, improving the efficiency of email communications.

Implementing ARC

Implementing ARC involves several steps:

1. Update your email servers: Ensure that your email servers support ARC. Many modern email servers already offer this support, but you may need to make updates or configuration changes.
2. Configure your email servers to add and validate ARC headers for forwarded emails.
3. Monitoring and Maintenance.

Conclusion

ARC (Authenticated Received Chain) is an important tool for maintaining the trustworthiness and integrity of forwarded emails. It helps to preserve the results of authentication checks while email is being transmitted across different servers, thus protecting against spoofing and improving email deliverability. Implementing ARC along with other authentication protocols such as SPF, DKIM, and DMARC provides strong protection against cyber threats and enhances the security of email communications.