DMARC Policies : The Ultimate Email Gatekeeper

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DMARC (Domain-based Message Authentication, Reporting, and Conformance) is an email authentication protocol that is designed to give email domain owners the ability to protect their domain from unauthorized use, also known as email spoofing. Simply put, DMARC permits an email sender’s domain to publish a policy that details which mail servers are allowed to send emails on that domain’s behalf as well as what to do in the event that an email fails SPF (Sender Policy Framework) or DKIM (Domain-Keys Identified Mail) checks.

Leading email providers like Google, Yahoo, and Microsoft have widely adopted DMARC as an essential part of an overall email authentication strategy to help stop phishing and email fraud.  In-depth information about DMARC, including its features, advantages, and implementation strategies, will be provided in this blog.

How DMARC Works?

DMARC works by building upon the existing email authentication protocols of SPF and DKIM. While DKIM uses digital signatures to confirm the authenticity of an email message, SPF allows a domain owner to specify which mail servers are permitted to send email on behalf of their domain.

When an email is received, an email client first determines whether the SPF check was successful. If the email fails the SPF check, the email client then checks if the email passes the DKIM check. If the email passes either the SPF or DKIM check, it is considered a valid email and is delivered to the recipient’s inbox.

However, if the email fails both the SPF and DKIM checks, the email client checks if the sending domain has a published DMARC policy. The email client can then carry out the instructions specified in the DMARC policy, such as rejecting the email, designating it as spam, or delivering it to the recipient’s inbox, if the sending domain has a published DMARC policy.

DMARC Policies.

DMARC policies are published as TXT records in a domain’s DNS (Domain Name System) records. The DMARC policy specifies the following information:

  • The domain owner’s preferred handling of emails that fail SPF and DKIM checks (e.g., reject, quarantine, or accept)
  • The email addresses of the individuals or organizations that should receive failure reports (also known as aggregate reports)
  • The frequency at which aggregate reports should be sent

A DMARC policy can be published with one of the following three actions:

  • p=none: This policy allows email clients to continue to receive emails that fail SPF and DKIM checks, but requires the email client to generate a DMARC failure report. This is useful for monitoring and tracking the use of a domain for unauthorized purposes.
  • p=quarantine: This policy instructs email clients to mark emails that fail SPF and DKIM checks as spam. This is useful for blocking phishing and other malicious emails.
  • p=reject: This policy instructs email clients to reject emails that fail SPF and DKIM checks, and not deliver them to the recipient’s inbox. Although this is the option with the highest level of security, it can also lead to false positives, where legitimate emails are mistakenly ignored.

Example DMARC Policy:

Here is an example of a DMARC policy for the domain example.com:

_dmarc.example.com. TXT “v=DMARC1; p=quarantine; pct=100; rua=mailto:dmarc-reports@example.com; ruf=mailto:dmarc-reports@example.com; sp=none; fo=1; rf=afrf; adkim=r; as =s; ri=86400”

In this example, the DMARC policy is set to “quarantine” with a 100% enforcement percentage. The aggregate reports will be sent to dmarc-reports@example.com, and the reports will use the Authentication Results Format (ARF). The policy also specifies that DKIM alignment should be relaxed and SPF alignment should be strict. The reports will be delivered daily, with a 86400-second reporting interval. 

Benefits of implementing DMARC.

There are several benefits to implementing DMARC in your organization, including:

  • Protects against email spoofing: DMARC helps to prevent email spoofing by allowing domain owners to specify which mail servers are authorized to send emails on behalf of their domain.
  • Prevents phishing attacks: Phishing attacks often involve the use of a spoofed email address to trick the recipient into providing sensitive information. By enabling email clients to reject or mark as spam emails that fail SPF and DKIM checks, DMARC helps to prevent phishing attacks.
  • Increases brand protection: DMARC helps to protect a domain owner’s brand by ensuring that emails sent from their domain are legitimate and not being used for malicious purposes.
  • Improves email deliverability: By reducing the number of phishing and malicious emails that are sent from a domain, DMARC can help to improve email deliverability by reducing the risk of emails being marked as spam or rejected.
  • Provides detailed reports: DMARC provides detailed reports that can be used to monitor and track the use of a domain for unauthorized purposes.

Implementing DMARC.

Implementing DMARC in your organization involves the following steps:

  • Set up SPF and DKIM: In order for DMARC to work, your organization must have both SPF and DKIM set up and configured correctly.
  • Publish a DMARC policy: Your organization will need to publish a DMARC policy in its DNS records, specifying the desired handling of emails that fail SPF and DKIM checks, the email addresses that should receive DMARC reports, and the frequency of reports.
  • Monitor DMARC reports: Your organization should regularly monitor DMARC reports to ensure that the policy is working as expected and to detect any potential abuse of your domain.
  • Adjust the DMARC policy as necessary: Your organization may need to adjust the DMARC policy as needed, based on the results of the DMARC reports and the overall email authentication strategy.

DMARC is an important component of an overall email authentication strategy that helps to protect a domain from unauthorized use, prevent phishing and email fraud, and improve email deliverability. Increased brand protection and the capacity to watch over and track any unauthorized use of your domain are just two advantages of implementing DMARC in your company.

DMARC implementation is strongly advised if your company is worried about email security and wants to safeguard its reputation. By taking the necessary steps to set up and configure DMARC, you can help to ensure that your domain is protected and that your emails are delivered as intended.

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