What Is DMARC? A Simple Guide to Email Protection

More than 300 billion emails are sent daily, making it one of the most prevalent communication channels worldwide. Unfortunately, this popularity also makes email a prime target for cybercriminals who exploit it through phishing, spoofing, and other fraudulent activities. 

In this article, we answer the question: What is DMARC, and why is DMARC important for securing your email communications and maintaining your brand’s reputation?

What is DMARC?

Domain-based Message Authentication, Reporting, and Conformance (DMARC) is an email authentication protocol designed to combat email fraud and phishing attacks. It allows email senders to specify policies for how their email should be handled if it’s received by a receiving server.

By verifying email senders and providing detailed reports on email activity, DMARC helps organizations improve email security and protect their domain reputation. Many businesses rely on trusted DMARC providers to help configure and manage these policies effectively. DMARC enables domain owners to set specific policies for how their emails should be authenticated and how to handle unauthorized messages. Essentially, DMARC allows companies to say:
“Emails from our domain must meet these specific criteria. If they don’t, they should be treated as suspicious.” For instance, HMRC estimates that the number of phishing emails sent from their domain decreased by 500 million in just 1.5 years after the implementation of DMARC.

DMARC builds on two existing protocols, SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail), to ensure that only authorized senders can use a domain. It’s an added layer of security but not a replacement for antivirus or firewall solutions. Organizations can use DMARC to specify actions for emails that fail authentication, such as rejecting, quarantining, or delivering them.

What Does DMARC Stand For?

DMARC stands for Domain-based Message Authentication, Reporting, and Conformance.

Each part of the acronym reflects a critical aspect of how DMARC works:

• Domain-based: DMARC runs at the domain level. The domain owner publishes a policy in their DNS record defining their email authentication practices and specifying how receivers should handle mail that fails authentication.
• Message Authentication: DMARC allows domain owners to designate the authentication protocols. These are used to validate incoming email messages. SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) are two such protocols. DMARC checks for alignment, meaning the domain in the “From” header must match the domain verified by SPF and/or DKIM.
• Reporting: You can enable feedback reports within your DMARC configuration. Following this, receiving MTAs will send over XML reports to your defined email address. These reports may contain DMARC aggregate (providing summaries of authentication results) or forensic data (providing details on individual failures).
• Conformance: Email domain owners can use DMARC to describe the actions (policy) for receiving mail servers. These actions (e.g., none, quarantine, reject) are implemented once an email fails the DMARC authentication and alignment checks.

Why is DMARC Important?

DMARC plays a critical role in enhancing email security by:

• Preventing email spoofing and phishing: By verifying the authenticity of emails claiming to originate from a specific domain, DMARC effectively thwarts spoofing attempts where attackers impersonate legitimate senders. This helps prevent phishing attacks that aim to steal sensitive information like login credentials and financial data. Statistics show roughly 1.2% of all emails sent are malicious, translating to 3.4 billion phishing emails per day.
• Improving email deliverability: By ensuring that only legitimate, authenticated emails from your domain reach inboxes, DMARC reduces the chances of your legitimate emails being flagged as spam. This improves your email deliverability rates and ensures that your messages reach the intended recipients.
• Protecting your brand reputation: By preventing unauthorized use of your domain for malicious activities like spam or phishing, DMARC safeguards your brand’s reputation and builds trust with your customers and partners.
• Providing valuable insights: DMARC generates comprehensive reports that provide valuable insights into your email sending activity across the internet. These reports help you identify and address potential issues like unauthorized senders, spoofing attempts, authentication misconfigurations, and compromised accounts.
• Meeting industry compliance requirements: DMARC is becoming increasingly important for compliance with industry standards and email provider requirements. Major email providers like Google and Yahoo may enforce stricter handling or even reject emails from domains that lack proper DMARC implementation.

By implementing and maintaining a robust DMARC policy, businesses can significantly enhance their email security posture, protect their brand reputation and customers, and ensure the effective delivery of legitimate email communications.

Simplify DMARC with PowerDMARC!

How DMARC Works

DMARC enhances email security by adding a layer of policy enforcement and reporting on top of existing authentication methods: SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail). A sender domain publishes a DMARC record in DNS specifying its policy. When an email is sent claiming to be from that domain:

1. Email Sending & Initial Checks: The sending server typically applies DKIM signatures. The email undergoes standard transit.
2. Email Reception & Authentication: The receiving server performs the following checks:
   • SPF Check: Verifies if the sending IP address is listed in the domain’s SPF record.
   • DKIM Check: Validates the email’s digital signature using the public key in the domain’s DNS to ensure it hasn’t been tampered with.
   • Alignment Check: DMARC requires identifier alignment. This means the domain used in the ‘From’ header (visible to the user) must match the domain validated by SPF and/or the domain specified in the DKIM signature (d= tag). An email can pass SPF or DKIM individually but still fail DMARC if the domains don’t align.
3. DMARC Policy Enforcement: The receiving server checks the sender domain’s DMARC record in DNS.
   • If the email passes SPF or DKIM checks *and* achieves alignment for at least one of them, it passes DMARC and is typically delivered normally.
   • If the email fails both SPF and DKIM, or fails alignment for both, the receiving server applies the DMARC policy specified in the sender’s DMARC record (e.g., p=none for monitoring, p=quarantine to send to spam, or p=reject to block the email).
4. Reporting: The receiving server generates aggregate (RUA) reports summarizing authentication data (pass/fail counts, IPs, alignment results) and potentially forensic (RUF) reports detailing individual failures. These reports are sent to the addresses specified in the sender domain’s DMARC record.

Many organizations choose to simplify and automate this entire process using solutions like PowerDMARC. For example, UK-based Managed Service Provider PrimaryTech partnered with PowerDMARC to streamline the management of SPF, DKIM, and DMARC records across multiple client domains. 

This not only helped them ensure accurate DNS record configuration and policy enforcement but also enhanced their clients’ email deliverability and protection against spoofing attacks, demonstrating the real-world impact of effective DMARC implementation.

How to Configure DMARC?

Here’s a step-by-step breakdown of how to configure DMARC:

1. Configure SPF and DKIM

Before implementing DMARC, ensure SPF and DKIM are properly configured for your domain and all legitimate sending sources:

• SPF: Defines which IP addresses and servers are authorized to send emails on behalf of your domain.
• DKIM: Adds a digital signature to your emails, verifying the sender and ensuring the message hasn’t been tampered with during transit.

These protocols form the foundation for DMARC. DMARC requires at least one of SPF or DKIM to pass and align, though implementing both is strongly recommended for enhanced security. Ensure you identify *all* legitimate email sources (including third-party services like marketing platforms or CRMs) and authorize them via SPF/DKIM.

2. Create a DMARC Record

A DMARC record is a TXT (Text) record published in your domain’s DNS (Domain Name System) settings. It specifies your email authentication policy. It includes:

• Mandatory Tags:
  • v=DMARC1: Indicates the DMARC version (currently always DMARC1).
  • p=none/quarantine/reject: Defines the policy for handling emails that fail DMARC authentication and alignment checks.
• Optional but Recommended Tags:
  • rua=mailto:dmarc-agg@example.com: Specifies the email address(es) for receiving aggregate reports (XML format). Multiple addresses can be listed, separated by commas.
  • ruf=mailto:dmarc-forensic@example.com: Specifies the email address(es) for receiving forensic reports (detailed failure reports, also XML). Support for RUF varies among receivers due to privacy concerns.
  • pct=100: Specifies the percentage of failing emails to which the DMARC policy should be applied (e.g., pct=20 applies the policy to 20% of failing mail). Allows for gradual policy rollout. Default is 100.
  • sp=none/quarantine/reject: Defines the policy for subdomains if not explicitly defined by a subdomain DMARC record. If omitted, the main domain policy (p=) applies to subdomains.
  • adkim=r/s: Specifies strict (s) or relaxed (r) alignment for DKIM. Relaxed (default) allows subdomain alignment.
  • aspf=r/s: Specifies strict (s) or relaxed (r) alignment for SPF. Relaxed (default) allows subdomain alignment.

You can use online tools to help generate your DMARC record syntax correctly.

3. Select a DMARC Policy

DMARC policies tell email receivers how to handle messages that fail DMARC checks (authentication failure or alignment failure). You should start with ‘none’ and gradually increase strictness:

• p=none (Monitoring Mode): Receivers take no specific action based on DMARC failure but send reports. This is the essential first step for discovering legitimate sending sources, identifying authentication issues, and understanding your email ecosystem without impacting mail delivery. Monitor reports carefully.
• p=quarantine: Instructs receivers to treat failing emails with higher suspicion, often moving them to the spam or junk folder. This is an intermediate step towards full enforcement.
• p=reject: Instructs receivers to block/reject emails that fail DMARC checks entirely. This is the strictest policy and offers the highest level of protection against spoofing, but should only be implemented after thorough monitoring confirms all legitimate mail passes DMARC.

4. Publish Your DMARC Record

Once your DMARC record is created, publish it in your DNS settings as a TXT record:

• Host/Name Field: Enter _dmarc (e.g., _dmarc.yourdomain.com).
• Record Type: Select TXT.
• Value/Data Field: Paste your DMARC record string (e.g., “v=DMARC1; p=none; rua=mailto:report@yourdomain.com;”).
• TTL (Time to Live): Typically set to 1 hour (3600 seconds) or your DNS provider’s default.

This makes your DMARC policy accessible to email receivers worldwide.

5. Verify Your DMARC Setup

Use a DMARC checker tool online to verify your DMARC record is correctly published in DNS and the syntax is valid. This step helps identify and resolve any configuration errors quickly.

6. Enable and Monitor Reporting

Ensure your DMARC record includes the `rua` tag pointing to a dedicated mailbox to receive aggregate reports. These reports, typically sent daily in XML format, are crucial for monitoring:

• Aggregate Reports (rua): Provide an overview of email authentication results from various receivers, including IP addresses sending mail claiming to be from your domain, SPF/DKIM pass/fail counts, and alignment status. Analyzing these reports (often with a DMARC analyzer service) helps identify legitimate sending sources needing configuration adjustments and spot unauthorized use.
• Forensic Reports (ruf): Offer detailed information (including headers and sometimes content snippets) about specific individual email delivery failures. Due to volume and privacy concerns, not all receivers send RUF reports, and processing them requires careful handling.

Regularly review reports, especially after starting with `p=none`, to fix SPF/DKIM/alignment issues for legitimate senders before moving to `p=quarantine` or `p=reject`. Keep DNS records accurate and up-to-date as sending sources change.

What Does DMARC Record Look Like?

The structure of a DMARC record is defined in the DNS (Domain Name System) as a TXT record associated with the domain, specifically at the `_dmarc` subdomain. It contains several tag-value pairs separated by semicolons, including ones that specify the policy mode and reporting options. Here’s an example of what a DMARC record might look like:

_dmarc.example.com. IN TXT “v=DMARC1; p=reject; rua=mailto:dmarc-agg@example.com; ruf=mailto:dmarc-forensic@example.com; sp=reject; pct=100; adkim=r; aspf=r;”

In this example:

• “_dmarc.example.com.” specifies the DNS hostname for the DMARC record of “example.com.”
• “IN TXT” indicates the record type as a text record.
• “v=DMARC1” signifies the DMARC protocol version being used is version 1. This tag is mandatory.
• “p=reject” sets the DMARC policy for the main domain to “reject”. This instructs receiving email servers to reject emails that fail DMARC checks for example.com. This tag is mandatory.
• “rua=mailto:dmarc-agg@example.com” specifies the email address as the destination to receive aggregate reports (summaries of authentication results). This tag is highly recommended for monitoring.
• “ruf=mailto:dmarc-forensic@example.com” designates the email address as the destination to receive forensic reports (details on individual failures). This tag is optional.
• “sp=reject” sets the subdomain policy to “reject,” ensuring that this DMARC policy also applies strictly to subdomains (e.g., mail.example.com), unless they have their own DMARC record. This tag is optional.
• “pct=100” indicates that the policy (reject in this case) should apply to 100% of emails failing DMARC checks. Optional; defaults to 100.
• “adkim=r” sets DKIM alignment requirement to relaxed (subdomain matches allowed). Optional; defaults to relaxed (r).
• “aspf=r” sets SPF alignment requirement to relaxed (subdomain matches allowed). Optional; defaults to relaxed (r).

DMARC, SPF, and DKIM: The Trio of Email Security

Implementing DMARC, SPF, and DKIM together creates a powerful, multi-layered defense against email spoofing, phishing, and other email-based threats. While DMARC technically only requires one of SPF or DKIM to pass and align, using all three is essential for robust email security:

1. Comprehensive Protection
   • SPF verifies that emails are sent from IP addresses authorized by the domain owner.
   • DKIM ensures email integrity by adding a cryptographic digital signature that confirms the message hasn’t been tampered with and verifies the signing domain.
   • DMARC builds upon SPF and DKIM by checking for domain alignment (matching the ‘From’ header domain) and enforcing domain owner policies (none, quarantine, reject) based on SPF/DKIM results and alignment. It also provides reporting.

   This combination offers strong protection against various forms of spoofing, phishing, and unauthorized senders. DMARC provides the crucial policy and reporting layer that SPF and DKIM lack on their own.

2. Enhanced Email Deliverability
   By properly authenticating emails using SPF and DKIM, and signaling this via a DMARC policy, organizations demonstrate legitimacy to receiving mail servers. This reduces the chances of legitimate emails being incorrectly flagged as spam or rejected, ensuring messages reach the intended recipients.
3. Brand Reputation Protection
   Email spoofing and phishing attacks using a company’s domain can severely damage its brand reputation and erode customer trust. SPF, DKIM, and DMARC work together to prevent unauthorized use of the domain in the ‘From’ field, safeguarding the brand’s integrity.
4. Improved Security Posture
   These protocols collectively make it much harder for malicious actors to successfully send fraudulent emails impersonating your domain. By ensuring only legitimate, authenticated emails conforming to policy are delivered, they strengthen overall email security and reduce the risk of email-borne cyber threats impacting recipients.
5. Reporting and Visibility
   A key advantage of DMARC is its reporting capability. It provides detailed aggregate (and optionally forensic) reports on authentication results (SPF, DKIM, DMARC pass/fail, alignment) for mail claiming to be from your domain. This visibility helps identify configuration issues, legitimate third-party senders needing setup, and malicious activity, enabling a continuously improving email security strategy.

Why Use All Three?

DMARC, SPF, and DKIM work best as a cohesive system:

• SPF addresses the question: “Is this email coming from an authorized server IP for the domain?”
• DKIM addresses the question: “Was this email signed by the domain owner and has it been altered in transit?”
• DMARC addresses the questions: “Do the domains authenticated by SPF/DKIM align with the ‘From’ address?” and “What should I do if the email fails these checks, and where should I send reports?”

Key Benefits at a Glance

By implementing all three protocols correctly, organizations create a strong defense against email threats while improving deliverability, protecting their brand, and gaining valuable insights into their email ecosystem.

Common DMARC Mistakes and How to Avoid Them

Implementing and managing DMARC can be complex, and even experienced administrators run into common pitfalls. This practical guide highlights real-world issues that can make or break the effectiveness of your DMARC setup. Understanding these mistakes and how to avoid them will help you get the most out of DMARC and keep your email domain secure.

Misconfiguring Your Policy

One of the most frequent errors is misconfiguring the DMARC policy in your DNS record. This could mean using incorrect syntax, unsupported tags, or missing required tags like v= (which specifies the DMARC version) and p= (which sets the policy action, such as none, quarantine, or reject).

Incorrect or missing policy tags can cause serious issues, from emails not being properly enforced to legitimate messages failing to deliver. Ensuring your policy syntax is correct and only includes supported tags is essential for DMARC to work as intended.

Not Monitoring Reports

Many organizations set up DMARC but then overlook the critical step of monitoring reports. Enabling and regularly reviewing DMARC aggregate (rua) and forensic (ruf) reports is key to understanding how your domain is being used or abused.

Ignoring these reports means missing out on valuable insights about failing authentication attempts, unauthorized senders, and misaligned sources. Since DMARC reports come in XML format, their complexity often leads to neglect. Using user-friendly tools and dashboards like Postmark, DMARCian, or similar services can turn this data into actionable insights that strengthen your email security.

Forgetting SPF/DKIM Alignment

It’s important to remember that DMARC is not just about having SPF (Sender Policy Framework) and DKIM (DomainKeys Identified Mail) configured; it requires proper alignment. This means the domain in the visible “From” address must match the domain authenticated by SPF and/or DKIM.

Even if SPF and DKIM pass individually, DMARC will fail if the domains don’t align correctly. Misunderstanding or overlooking alignment can lead to unexpected failures and impact your email deliverability.

Moving to ‘Reject’ Too Quickly

Jumping straight to a strict p=reject policy without sufficient monitoring can backfire. Without collecting data in none or quarantine mode first, you risk blocking legitimate emails, especially from third-party services like CRMs (Customer Relationship Management), marketing platforms, or support tools that may not be fully configured.

A gradual approach is best: start with p=none to gather reports, carefully review and fix issues, then move to p=quarantine, and finally to p=reject once you’re confident all legitimate senders pass authentication. This staged rollout ensures smooth enforcement without disrupting your email flow.

PowerDMARC’s Cloud-Based DMARC Solution

As a business owner maintaining an online domain, having DMARC implemented serves as a feather in your cap in terms of security. While you can do so manually, there are certain additional benefits of choosing a third-party vendor like PowerDMARC. With us, you get a host of reporting, management, and monitoring facilities at a very affordable rate. These don’t fall within the scope of a manual DMARC setup and can really make a difference for your business!

By configuring our DMARC analyzer you can:

1. Configure hosted DMARC and other email authentication protocols easily
2. Monitor your authentication results through simplified, human-readable reports parsed from complex XML data
3. Get real-time alerts on email, slack, discord, and webhooks for failures or policy changes
4. Improve your email deliverability over time by identifying and fixing authentication issues

Our customers enjoy dedicated support from our in-house DMARC experts to configure the solutions tailored to their needs. Get in touch with us today for a free DMARC trial!

“Extensively searched for a high-value DMARC platform and found it!”

Dylan B.

Frequently Asked Questions

Is DMARC required by law?

DMARC is not legally required in most countries, but many industries and organizations adopt it as a best practice to protect their email domains and customers from phishing and spoofing.

Can DMARC stop all phishing attacks?

While DMARC significantly reduces phishing by blocking unauthorized senders, it can’t stop every attack. Some phishing tactics bypass email authentication, so DMARC should be part of a broader security strategy.

How long does it take to implement DMARC?

Implementation time varies—from a few hours for basic setup to several weeks for full monitoring, policy tuning, and alignment with all email sources. Careful planning and gradual enforcement help ensure success.

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Maitham Al Lawati

Maitham is a tech entrepreneur, cybersecurity expert, CEO and Founder of PowerDMARC with 15+ years of industry experience. Maitham holds a Global MBA from the University of Manchester and various professional certifications including CISSP, CISM, CRISC, and ISC2 CCSP.

Latest posts by Maitham Al Lawati (see all)

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