How Does DMARC Work?

Learn the technical specification of DMARC and how a DMARC policy works

Email Security > DMARC

How Does DMARC Work?

Email communication is a crucial aspect of daily operations when you run an organisation. You and your team exchange emails daily, which may contain sensitive information that could be compromised by various risks. Therefore, the security of your email communication becomes crucial.

By Cian Fitzpatrick | 3 August, 2023

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Taking the necessary measures to safeguard your email communication will help protect your organisation‚Äôs valuable data and maintain your stakeholders’ trust. Hence, DMARC services (Domain-based Message Authentication, Reporting, and Conformance) play a powerful solution to enhance your organisation‚Äôs email security.¬†

What is DMARC in email?

DMARC stands for Domain-based Message Authentication Reporting & Conformance, a security protocol used to authenticate an email. It protects domain owners from spam, phishing, and other email scams that can happen through email.

It combines two essential components such as SPF (Sender Policy Framework) and DKIM (Domain Keys Identified Mail), that provide a framework to verify the authenticity of incoming email messages. Take a look at our comprehensive DMARC guide to get all the necessary information.

What Are SPF, DNS and DKIM?

Through SPF (Sender Policy Framework), you can specify which IP addresses can send emails from your domain. When an email is received, the receiving email server checks the SPF record to verify if the sender’s IP address is authorised to send emails for that particular domain. If the email fails the SPF check, it is considered potentially fraudulent.

‚ÄúDNS (Domain Name System) acts as a phonebook for the internet. When you type a domain name like ‚Äú‚ÄĚ into your web browser, the DNS system translates that domain name into the corresponding IP address (such as that identifies the server where the website is hosted. ‚Äú

DKIM (Domain Keys Identified Mail) is an email authentication method that adds an extra layer of security by digitally signing outgoing emails with a private key and attaching the signature to the email headers. The recipient’s server then uses the public key published in the DNS to verify the authenticity and integrity of the email. This ensures that the message originated from the authorised domain.

However, SPF and DKIM alone cannot fully protect against email fraud. This is where DMARC plays an important role. It builds upon SPF and DKIM to provide a comprehensive framework for email authentication and policy enforcement.

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The Link Between DMARC, SPF, and DKIM in Email Authentication

DMARC, SPF, and DKIM work together to authenticate emails and prevent fraudulent activities.

  • SPF helps verify the sender‚Äôs IP address.
  • DKIM verifies the integrity and authenticity of the email, and
  • DMARC allows domain owners to set policies and receive reports on email authentication.


Together, these protocols prevent email fraud, phishing, and spoofing attacks, providing more secure email communication.

Technical Specifications of DMARC

DMARC is a flexible protocol that domain owners can customise based on their needs. The technical specifications of DMARC are as follows:

DMARC Record

A DMARC record is a simple text file that stores a domain’s DMARC policy. It instructs email receivers on what actions to take when an email fails DMARC authentication and where to send reports.

The DMARC record includes various parameters, such as the chosen DMARC policy, which determines how emails that fail DMARC validation are handled.

Policy Modes

DMARC allows domain owners to specify different policy modes if an email fails the SPF or DKIM process. There are three different policy modes, such as “None,” “Quarantine,” and “Reject.”


Two alignment checks known as SPF Alignment and DKIM Alignment ensure the “From” header domains match the authenticated domains used in SPF and DKIM.


DMARC sends reports to domain owners known as “Aggregate Reports” and “Failure Reports”. These reports provide SPM and DKIM statistics, alignment results, sending sources, and more.

Subdomain Policy

DMARC allows domain owners to specify separate policies for subdomains to enable control over email authentication for different subdomains.

DMARC Tag-Value Syntax

DMARC uses a specific syntax to provide instructions or information. The common tags used in DMARC records include “v” for protocol version, “p” for policy, “rua” for aggregate report addresses, “ruf” for failure report addresses, and “sp” for subdomain policies.

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How Does DMARC Work?

DMARC offers domain owners and organisations a framework to specify how email receivers should handle unauthenticated emails that claim to come from their domain. It helps to ensure the safety and security of email communication.

Here’s a step-by-step explanation of how DMARC works:

  • Setting up DMARC Record: The domain owners add DMARC records to the DNS zone file. The record includes the DMARC policy for the domain and provides instructions to email receivers on handling incoming emails from that domain.

  • Incoming Email: When receiving an email, the server checks whether the DMARC record is in the sender’s domain DNS.

  • SPF and DKIM Checks: The recipient‚Äôs email server then performs SPF and DKIM checks for the email‚Äôs authenticity. SPF validates the sender‚Äôs IP address, while DKIM verifies the digital signature associated with the email.


  • DMARC Alignment: Once the SPF and DKIM checks are completed, DMARC checks if the “From” header domain matches the domain authorised in the SPF and DKIM checks. The DMARC alignment ensures the email is sent from an authorised sender and hasn‚Äôt been spoofed.

  • DMARC Policy Evaluation: The recipient‚Äôs email server evaluates the SPF and DKIM results based on the specified DMARC policy. There are three types of DMARC policies:

    • None Policy (“p=none”): In the None policy, no specific action is taken on unauthenticated emails. However, reports are still generated and sent to the domain owner for monitoring.

    • Quarantine Policy (“p=quarantine”): Under Quarantine policy, an email that fails authentication is considered suspicious and placed in the recipient‚Äôs spam or quarantine folder.

    • Reject Policy (“p=reject”): When the Reject policy is specified, all unauthenticated emails are immediately rejected and do not reach the recipient‚Äôs inbox. They are outright discarded to protect against potential phishing attacks.

  • DMARC Reporting: The recipient‚Äôs email server generates DMARC aggregate reports that contain insights into the email traffic, authentication results, and potential attacks. These reports are sent to the administrator‚Äôs email address.

  • Monitoring and Conformance: DMARC allows domain administrators to monitor the DMARC reports received from servers regularly. By analysing the reports, they can identify unauthorised email sources, detect potential email spoofing, and identify configuration issues.

This process enhances security, improves email deliverability, and maintains compliance with DMARC policy. 

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How to Check DMARC?

It is essential to regularly check the DMARC configuration, review reports, and make any necessary adjustments for better efficiency and proper implementation.

Different Methods and Tools for Checking DMARC

  • Perform DNS Lookup: You can perform a DNS lookup for the DMARC record of the domain by using various online DNS lookup tools or command-line tools like ‚Äėnslookup‚Äô or ‚Äėdig‚Äô to retrieve the DMARC record of the domain you want to check.

  • Analyse the DMARC Record: To understand the policy and configuration settings better, manually review the DMARC record that has been published. Look for these tags that provide information about the DMARC policy and reporting preferences:

    • “v” (version)
    • “p” (policy)
    • “pct” (percentage)
    • “rua” (aggregate report URI)
    • “ruf” (forensic report URI)


  • Validate SPF and DKIM Alignment: Check if the domain has been correctly implemented in SPF and DKIM. Ensure that SPF and DKIM are properly configured and aligned with the “From” domain specified in the DMARC record.

Tools such as SPF validators and DKIM checkers help validate the records and ensure they are correctly set up.

  • Review DMARC Reports: When your domain has implemented DMARC, you will receive DMARC aggregate reports from email receivers. Analyse these reports regularly to identify any issues or authentication failures.

  • Use DMARC Analyzers: Utilise online DMARC analyzer tools, such as DMARC Analyzer, to simplify the checking process. These tools will analyse your domain configuration, provide a summary, or underline any potential attacks.

  • Implement DMARC Monitoring: Use DMARC monitoring services that monitor your DMARC implementation. You will receive real-time alerts for issues or any changes to the DMARC record and analytics to help you track the performance of your DMARC setup.

How Does DMARC Enhance Email Deliverability?

  • ¬†DMARC enhances email deliverability in the following ways:

    • DMARC reduces email spoofing, thus protecting a brand’s reputation.

    • Ensures legitimate email reaches the intended recipient‚Äôs inbox rather than spam.

    • Establish trust in email providers and ISPs, which can positively influence email deliverability as they prioritise email from trusted domains.

    • Helps the domain owner identify sources of unauthorised email or attempted email spoofing.

DMARC and Phishing

Many malicious attackers attempt to deceive recipients into sharing sensitive information, such as financial details or login credentials, by impersonating them via email. DMARC plays a crucial role in combating these phishing attacks.

Does DMARC protect against phishing?

  • ¬†Implementing DMARC protects against phishing. It protects recipients from being victims of a phishing attempt and safeguards domain reputations. Here‚Äôs how DMARC helps mitigate phishing attacks:

    • DMARC quickly identifies legitimate emails, making it difficult for phishing emails to pass through authentication checks.

    • As DMARC verifies the “FROM” header, it ensures that the email hasn‚Äôt been compromised or spoofed in transit. Often, phishing emails involve domain spoofing to trick recipients, but DMARC‚Äôs alignment makes it harder for them to impersonate legitimate domains.

    • DMARC policies also play an important role, as they automatically discard any potentially harmful emails, thus reducing the chances of these emails reaching recipients.

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Benefits of DMARC

  • DMARC provides a strong email authentication framework by combining SPF and DKIM protocols. It ensures the email has not been tampered with and protects against fraudulent activities.

  • Implementing DMARC enhances legitimate email deliverability rates and reduces the risk of emails being flagged as spam.

  • DMARC protects organisations‚Äô brand reputations by reducing phishing and spoofing attempts and maintaining the integrity of customers and stakeholders.

  • DMARC generates aggregate reports that help domain owners identify and address security threats and enhance email security.

Limitations of DMARC

  • Setting up and configuring DMARC records, SPF, and DKIM can be difficult, especially for organisations with multiple domains or complex email infrastructure. It may require numerous back-and-forth communications between email service providers to adopt DMARC effectively.

  • If a company uses third-party services such as email marketing campaigns and does not correctly configure the DMARC setting, it will not effectively protect its brands.

  • In some cases, legitimate emails may be marked as spam or rejected due to misconfigurations or misinterpretations of DMARC policies. Organisations should carefully monitor and adjust their DMARC policies to avoid unintended consequences.

  • DMARC primarily focuses on email-based attacks, such as phishing or spoofing attempts. It does not protect a company against non-email-based attacks such as scams on social media or SMS phishing attacks.

How to Choose a DMARC Service Provider?

Selecting a DMARC service provider is a crucial process that requires domain owners to evaluate various factors carefully.

Below are some checklists to consider while choosing a DMARC service provider:

  • Look for a provider with a good track record of assisting organisations with DMARC deployment and expertise in understanding industry best practises.

  • Ensure the service provider offers comprehensive DMARC capabilities, including DMARC reporting, monitoring, and analysis.

  • Consider whether the DMARC service provider can accommodate your organisation‚Äôs growth and scale as your email volume increases.

  • Assess the level of customer service provided by the DMARC service provider to see if they offer assistance and are available to address your issues.

  • Evaluate their pricing plan and features with different providers to ensure you get value for your investment.

  • Check out if they provide additional features or services, such as security enhancement or email deliverability consulting, that enhance your email security strategy.

  • The most important one is that you need to re-review their data handling and privacy policies to ensure the confidentiality of your email data.

An Overview of Topsec DMARC Services

Topsec Cloud Solutions offers comprehensive DMARC services to address businesses’ email security concerns. As the only managed email service provider, we provide an end-to-end service, ensuring that all your email security needs are met efficiently. Our DMARC services leverage AI and machine learning models for ultimate threat protection, analysing millions of emails daily.

Partner with Topsec for reliable and effective DMARC services, enhancing your email security framework with our expertise and AI-driven approach. Our technical professionals are available 24/7, providing round-the-clock support. Let us manage your entire DMARC process, so you can focus on your business needs.

The Future of DMARC and Email Security

Many organisations are realising the importance of DMARC and are rapidly adopting it. The evolution of email authentication protocols like SPF, DKIM, and DMARC will result in a stronger mechanism for verifying email authenticity, which makes email communication more secure.

DMARC will play a central role in comprehensive email security frameworks, integrating with advanced threat detection technologies, machine learning, and artificial intelligence. This layered approach will enhance overall email security and safeguard against emerging threats.

The future of DMARC and email security is dynamic. With increased technological advancements, collaboration, and user education, DMARC will continue to be a critical component of email security strategies, ensuring secure and trustworthy communications channels for domain owners and organisations.

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Yes, DMARC relies on SPF (Sender Policy Framework) and DKIM (Domain Keys Identified Mail) to ensure the authenticity of the sender’s domain. SPF verifies the sender’s IP address, and DKIM verifies the integrity of the email’s digital signature. SPF and DKIM work together to provide a layered approach to email authentication, and DMARC builds upon their foundations to enforce policies and provide reporting capabilities.

DMARC works by verifying the authenticity of emails through SPF and DKIM checks and aligning the “From” header domain with the authorised domains. It enforces policies for handling unauthenticated emails, such as marking them as spam, quarantining them, or outright rejecting them. DMARC also generates aggregate reports that provide insights into email authentication results, sources of abuse, and potential configuration issues.

Email receivers primarily implement DMARC to check the presence of a DMARC record in the sender’s domain DNS. However, it also allows senders to control how they handle unauthenticated emails.

Thus, it collaborates between senders and receivers to enhance email security and deliverability.

A domain should have only one DMARC record. Having multiple records for the same domain can lead to inconsistent policies, and email receivers won’t know which one to follow. This will lead to potential deliverability issues and misinterpretations of intended policies. If you need to modify your DMARC policy or configuration, updating the existing DMARC record is recommended rather than creating additional ones.