Amazon SES Now Supports DMARC Validation and Reporting for Incoming Email

Amazon SES now adds DMARC verdicts to incoming emails, and publishes aggregate DMARC reports to domain owners. These two new features will help combat email spoofing and phishing, making the email ecosystem a safer and more secure place.

What is DMARC?

DMARC stands for Domain-based Message Authentication, Reporting, and Conformance. The DMARC standard was designed to prevent malicious actors from sending messages that appear to be from legitimate senders. Domain owners can tell email receivers how to handle unauthenticated messages that appear to be from their domains. The DMARC standard also specifies certain reports that email senders and receivers send to each other. The cooperative nature of this reporting process helps improve the email authentication infrastructure.

How does Amazon SES Implement DMARC?

When you receive an email message through Amazon SES, the headers of that message will include a DMARC policy verdict alongside the DKIM and SPF verdicts (both of which are already present). This additional information helps you verify the authenticity of all email messages you receive.

Messages you receive through Amazon SES will contain one of the following DMARC verdicts:

• PASS – The message passed DMARC authentication.
• FAIL – The message failed DMARC authentication.
• GRAY – The sending domain does not have a DMARC policy.
• PROCESSING_FAILED – An issue occurred that prevented Amazon SES from providing a DMARC verdict.

If the DMARC verdict is FAIL, Amazon SES will also provide information about the sending domain’s DMARC settings. In this situation, you will see one of the following verdicts:

• NONE – The owner of the sending domain requests that no specific action be taken on messages that fail DMARC authentication.
• QUARANTINE – The owner of the sending domain requests that messages that fail DMARC authentication be treated by receivers as suspicious.
• REJECT – The owner of the sending domain requests that messages that fail DMARC authentication be rejected.

In addition to publishing the DMARC verdict on each incoming message, Amazon SES now sends DMARC aggregate reports to domain owners. These reports help domain owners identify systemic authentication failures, and avoid potential domain spoofing attacks.

Note: Domain owners only receive aggregate information about emails that do not pass DMARC authentication. These reports, known as RUA reports, only include information about the IP addresses that send unauthenticated emails to you. These reports do not include information about legitimate email senders.

How do I configure DMARC?

As is the case with SPF and DKIM, domain owners must publish their DMARC policies as DNS records for their domains. For more information about setting up DMARC, see Complying with DMARC Using Amazon SES in the Amazon SES Developer Guide.

DMARC reporting is now available in the following AWS Regions: US West (Oregon), US East (N. Virginia), and EU (Ireland). You can find more information about the dmarcVerdict and dmarcPolicy objects in the Amazon SES Developer Guide. The Developer Guide also includes a sample Lambda function that you can use to bounce incoming emails that fail DMARC authentication.