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What is DMARC and why is it important for your email security

Updated: Mar 31


What is DMARC

DMARC (Domain-based Message Authentication, Reporting, and Conformance) is an email authentication and reporting protocol that helps prevent email spoofing, phishing, and other fraudulent activities by allowing domain owners to set policies for email sources (such as email providers, i.e. Yahoo Mail, Outlook and Gmail, etc.) on how to handle emails that claim to be from their domain. DMARC works alongside SPF and DKIM to verify the authenticity of incoming emails and enables domain owners to specify actions for unauthenticated emails, such as quarantining or rejecting them. This enhances email security and protects both senders and recipients from potential email-based attacks.

What is DMARC

Journey of DMARC over the years

In 2007, SPF and DKIM were separately introduced to help combat email abuse and improve email deliverability. SPF focused on preventing sender address forgery, while DKIM added cryptographic signatures to emails to verify their authenticity. DMARC was proposed by a group of organizations, including PayPal, Google, Microsoft, Facebook, and Yahoo, to provide a standardized framework for email authentication and reporting 2012. The goal was to bring together SPF and DKIM to enhance email security and reduce domain spoofing. From 2012 to 2015, DMARC gained traction among email service providers and domain owners as a solution to prevent email-based attacks. Major email providers like Google and Microsoft began to support DMARC policies. Since 2015, DMARC adoption continued to grow, and it has become an essential tool in the fight against phishing and email fraud. Organizations across various industries, including financial services, government, and technology, embraced DMARC to protect their domains and users.


DMARC allows domain owners to publish policies that specify how email receivers should handle messages that fail authentication checks. It also provides valuable feedback through reporting mechanisms, allowing domain owners to monitor and analyze email activity related to their domains. It has played a pivotal role in improving email security, reducing domain impersonation, and enhancing the trustworthiness of digital communication. Its adoption continues to expand as businesses and organizations recognize its significance in safeguarding their online communications.



Why DMARC is important?

DMARC enhances email security, authenticity, and control while providing valuable insights to domain owners for maintaining a secure and reliable email ecosystem.

Email Security

Here are the key benefits as follows:

  1. Email Security: DMARC helps protect against email phishing and spoofing attacks, reducing the risk of fraudulent emails reaching recipients.

  2. Authentication: It ensures that emails sent on behalf of a domain are authenticated, increasing the trustworthiness of email communications.

  3. Policy Enforcement: DMARC allows domain owners to set policies for handling unauthenticated emails, giving them control over email delivery.

  4. Visibility: DMARC provides detailed reports on email authentication results, helping domain owners identify and fix authentication issues.

  5. Brand Protection: By preventing unauthorized use of their domain, organizations can safeguard their brand reputation.

  6. Improved Deliverability: Implementing DMARC correctly can improve email deliverability rates as it reduces the chances of emails being marked as spam or rejected.

  7. Global Adoption: DMARC is widely supported, making it an effective and standardized solution for email authentication.


Security Risk without DMARC

Without DMARC, organizations are more susceptible to various risks related to email security and brand reputation.

Email Impersonation

Some of the key risks include:

  1. Phishing Attacks: Without DMARC, it becomes easier for malicious actors to impersonate an organization's domain and send phishing emails to trick recipients into disclosing sensitive information or downloading malicious content.

  2. Email Spoofing: Attackers can forge the "From" address in emails, making it appear that the email is sent from a legitimate source, leading to potential trust violations and damaging the organization's reputation.

  3. Loss of Customer Trust: If customers receive phishing emails purportedly from the organization, it can erode trust and confidence in the brand, leading to customer dissatisfaction and loss of business.

  4. Data Breaches: Phishing attacks can lead to successful data breaches, where sensitive information such as login credentials, financial data, or personal information can be stolen.

  5. Financial Fraud: Fraudulent emails, claiming to be from the organization, can deceive customers or employees into making unauthorized financial transactions.

  6. Blacklisting and Deliverability Issues: If attackers abuse the organization's domain for spam or phishing activities, email providers may blacklist the domain, affecting legitimate emails' deliverability.

  7. Damage to Brand Reputation: High-profile phishing attacks or email scams associated with the organization's domain can severely damage its reputation and credibility.

  8. Lack of Visibility: Without DMARC, organizations miss out on valuable insights and reports about email authentication, making it harder to identify and rectify email authentication issues and credibility.

  9. Damage to Brand Reputation: High-profile phishing attacks or email scams associated with the organization's domain can severely damage its reputation and credibility.


How does DMARC work?

The DMARC policy is a set of instructions that domain owners define to specify how email receivers (such as email providers) should handle incoming emails claiming to be from their domain. The policy can be set to one of three possible actions:

  • None: In "none" mode, the DMARC policy is set to monitor-only. Email receivers will not take any action on unauthenticated emails but will send DMARC aggregate reports to the domain owner. This allows the domain owner to analyze potential email authentication issues without impacting email delivery.

  • Quarantine: When the DMARC policy is set to "quarantine," email receivers may choose to deliver unauthenticated emails to the recipient's spam or junk folder instead of the inbox. This action helps protect recipients from potentially malicious emails.

  • Reject: In "reject" mode, email receivers will outright reject any email that fails DMARC authentication, ensuring that unauthenticated emails are not delivered to the recipient's inbox. This is the most secure setting and provides stronger protection against email-based attacks.

  • Approve: If the email meets the defined DMARC policy, then it is approved.

DMARC Policy
Source: Postmark App (https://postmarkapp.com/guides/dmarc)

Difference between SPF and DKIM:

SPF validates the sending mail server's IP address against the authorized list in the domain's SPF record, while DKIM verifies the integrity of the email's content using cryptographic signatures. SPF and DKIM are often used together with DMARC (Domain-based Message Authentication, Reporting, and Conformance) to provide comprehensive email authentication and protection against email spoofing and phishing attacks.

SPF (Sender Policy Framework)

DKIM (DomainKeys Identified Mail)

SPF is a simple email authentication protocol that relies on DNS (Domain Name System) records.

​DKIM uses cryptographic signatures to validate the integrity of the email's content and ensure that it hasn't been altered during transit.

When an email is received, the recipient's email server checks the SPF record of the sender's domain to verify if the sending mail server is authorized to send emails on behalf of that domain.

When an email is sent, the sender's domain adds a digital signature to the email header using a private key, which is stored in the domain's DNS records.

The SPF record contains a list of IP addresses or hostnames that are allowed to send emails for the domain. If the sender's IP address matches one of the entries in the SPF record, the email is considered authenticated.

When the email is received, the recipient's email server retrieves the public key from the sender's domain DNS and verifies the signature. If the signature is valid, it confirms that the email's content remains unchanged since it was signed.

SPF primarily validates the envelope sender, which is used in the SMTP (Simple Mail Transfer Protocol) communication, but not the content of the email itself.

DKIM focuses on validating the content of the email and provides a level of assurance that the email is from the claimed sender and hasn't been tampered with.


Which Organisations Need a DMARC Managed Service?

All organisations should implement DMARC, so any organisation is a potential client for this managed service, especially those that use 3rd parties to send emails to staff and/or customers. Organisations that invest in email marketing (e.g. Retail, B2C, and others) rely heavily on successfully delivering emails to their customers. For them, DMARC-compliant emails have significantly higher delivery rates.


Organisations using this service will have visibility to:

  • How many emails are being sent (from all sources, not just their mail server)?

  • How many emails are failing DMARC?

  • How many emails failing DMARC have been sent by hackers?

  • The detailed reasons why emails fail DMARC, enabling the fine tuning of their email authentication.


How Can Spartans Security Help?

Spartans Security helps businesses by providing a managed service that enables clients to achieve and maintain DMARC compliance.

Email Delivery

The service aggregates the DMARC email reports for a client’s domains and details DMARC compliance per email source. The service also identifies issues and non-compliant email source details in the form of tasks and the remediation required to maintain or enable a DMARC reject policy per domain.


With the reject policy applied, it becomes impossible for the email from that domain to be spoofed, protecting the client and their staff and customers from this common and very successful form of phishing.


The following per-domain service flow shows DNS changes and remediation in blue and the DMARC managed service in green.

Steps to DMARC Compliance

Conclusion

In summary, SPF validates the sending mail server's IP address against the authorized list in the domain's SPF record. At the same time, DKIM verifies the integrity of the email's content using cryptographic signatures. SPF and DKIM are often used with DMARC (Domain-based Message Authentication, Reporting, and Conformance) to provide comprehensive email authentication and protection against email spoofing and phishing attacks. In DMARC, alignment is crucial. It demands that the domains authenticated by SPF or DKIM match the domain in the email's From header. Unlike SPF and DKIM, which don't directly relate to the From address, DMARC ensures this alignment. If the domains don't match, DMARC fails, providing vital control against phishing and unauthorized domain use.

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