DMARK verification failed

Question

Dear Team, Message trace of Contoso.com fails with an error message "domain contoso.com does not pass DMARK verification and has DMARK policy reject". How can I setup my DMARK verification and DMARK policy for smooth mail flow within Contoso.com (office 365) domain. It's an internal mail flow.

Answer 1

Hello Team, So far I have received following information from a reliable resource. If an email fails DMARC (not DMARK) validation, it means it hasn't passed the DMARC policy set by the domain owner. Here are some steps to resolve mail flow issues in such cases:

1. Review DMARC Reports: Check DMARC reports regularly to understand which emails are failing authentication and the sources of these emails.
2. Check SPF and DKIM: Ensure that SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) are properly configured for your domain. SPF validates the sender's IP address, while DKIM verifies the integrity of the message content.
3. Identify Unauthorized Sources: Determine if the failing emails are coming from legitimate sources or if they're spoofed or malicious. This may involve investigating the sending IP addresses and domains.
4. Adjust DMARC Policy: Depending on your organization's risk tolerance, you can adjust your DMARC policy. You may start with a policy of "none" to monitor email traffic without impacting delivery, then gradually increase to "quarantine" or "reject" as you gain confidence in your email authentication setup.
5. Educate Users: Train users to recognize phishing attempts and report suspicious emails. User awareness is crucial in preventing successful email attacks.
6. Implement Email Authentication: Consider implementing additional email authentication measures such as BIMI (Brand Indicators for Message Identification) to enhance email security and brand protection.
7. Use DMARC Monitoring Tools: Utilize DMARC monitoring tools and services to gain insights into your email authentication status and receive alerts about potential issues.
8. Engage with Service Providers: If emails from legitimate sources are failing DMARC checks, engage with your email service providers or third-party vendors to ensure proper authentication configurations.

By following these steps, you can troubleshoot and resolve mail flow issues related to DMARC failures effectively.