What is DMARC? A detailed guide

What is DMARC & why is email authentication important?

Email authentication is essential because email is a primary communication channel and a major target for cybercriminals. Without authentication, threat actors can easily impersonate your company’s domain, which can lead to financial, operational, and reputational damage.

Example:

A small business owner discovers that customers are receiving fraudulent invoices that appear to come from her company’s email address. By implementing Domain-based Message Authentication, Reporting, and Conformance (DMARC), she stops these spoofed emails, protecting both her customers and her brand’s reputation.

What is DMARC: The basics

What is DMARC in email? DMARC is an email authentication protocol that protects domains from email spoofing and phishing attacks. By implementing DMARC, organizations ensure that only authorized senders can use their domain and that messages haven’t been tampered with during transit. DMARC also helps improve email deliverability and strengthen recipient trust.

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What is DMARC: Understanding what DMARC does

DMARC enables domain owners to set policies that tell receiving email servers how to handle messages that fail Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM) evaluations. So, what is DMARC doing behind the scenes? DMARC verifies whether incoming emails pass either SPF or DKIM and then applies the specified policy – monitor, quarantine, or reject – if authentication fails.

This process helps prevent unauthorized use of your company’s domain in email communications and protects against cyberthreats like phishing and spoofing.

In simple terms:

DMARC acts as a set of instructions for email providers. It tells them how to verify whether an email sent from your business’s domain is legitimate and what action to take if it’s not. This not only blocks unauthorized emails (when a policy of p=reject is enforced) but also provides visibility through reporting, allowing organizations to monitor email activity and identify potential misuse.

What is DMARC & how does it protect?

What is DMARC’s role in your company’s security stack? DMARC works by building on two key standards:
  • SPF: Verifies if the sender’s IP address is authorized to send emails on behalf of a domain
  • DKIM: Uses cryptographic signatures to confirm that an email hasn’t been altered during transit
DMARC combines these protocols and allows domain owners to:
  • Define how unauthenticated emails should be handled (monitored, quarantined, or rejected)
  • Receive reports on unauthorized email activity
  • Gradually enforce stricter security policies over time
When a DMARC policy is configured, email providers are instructed on how to handle emails that appear to come from your business’s domain but fail authentication checks:
Policy Action
p=none Take no action but send detailed reports to the domain owner
p=quarantine Send suspicious emails to the Spam or Junk folder
p=reject Block unauthenticated emails entirely
By understanding DMARC, domain owners gain more visibility into their email environments. It significantly reduces the likelihood of phishing and spoofed emails reaching inboxes, strengthens email security, and helps maintain brand trust and integrity.

What is DMARC: DMARC explained simply

Think of DMARC as passport control for your organization’s email domain. Every email claiming to come from your company’s domain has to present valid documentation in the form of SPF and DKIM records. If the credentials are valid, the email goes through. If not, it’s either turned away or held for inspection, protecting your business from impersonation attempts.

What is DMARC: Key benefits

  • Protects against phishing and spoofing: DMARC blocks cybercriminals from sending fake emails that appear to come from your organization’s domain. This reduces the risk of phishing and spoofing attacks, which can damage your company’s brand and compromise sensitive information.
  • Improves email deliverability: Authenticated emails are more likely to reach inboxes and avoid being marked as Spam or Junk.
  • Builds trust: When recipients see that your business’s emails are authenticated, they’re more likely to trust communications from its domain. This trust leads to higher engagement and protects your organization’s reputation.
  • Provides visibility: DMARC generates detailed reports that show who’s sending emails on behalf of your company’s domain, both legitimate and unauthorized. These insights help identify potential vulnerabilities and unauthorized activity.
  • Reduces risk: By stopping unauthorized emails and minimizing the chance of your business’s domain being used in cybercrime, DMARC helps safeguard your organization from financial loss, reputational damage, and regulatory issues.

Learn more about the protocol’s benefits with Sendmarc’s DMARC management platform.

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What is DMARC & when might your company encounter it?

It might encounter DMARC in multiple common scenarios:

  • If your business’s marketing team wants to ensure their emails reach customers’ inboxes, DMARC can help. It tells email providers that your organization’s messages are legitimate, so they’re less likely to be marked as Spam.
  • If your company has ever had a cybercriminal try to impersonate it, DMARC can help stop this. By verifying which emails are truly from your business, DMARC protects its reputation and prevents scammers from tricking its contacts.
  • If your organization’s goal is to keep its customers, business partners, or employees safe from email scams, DMARC is a key tool. It blocks most fraudulent emails before they reach anyone’s inbox.

Understanding DMARC, even without technical expertise, enables better decision-making and helps your company enhance its email security posture.

What is DMARC: FAQs

What does DMARC do?
DMARC protects your business’s domain from being used in phishing and spoofing attacks by verifying that emails claiming to be from its domain are actually authorized. It helps ensure only legitimate emails are delivered, reducing the chance of financial loss, data breaches, and reputational harm.

DMARC stops cybercriminals from sending fake emails that look like they’re from your organization, reducing the risk of phishing, fraud, and brand damage.

The DMARC definition is: An email authentication protocol that works with Sender Policy Framework (SPF) and DomainKeys Identified Mail (DKIM) to verify the legitimacy of emails sent from your company’s domain. SPF checks if the sender is authorized, while DKIM uses cryptographic signatures to confirm that the message hasn’t been tampered with.

A basic understanding of SPF and DKIM is helpful, but not strictly required to understand the purpose of DMARC. DMARC was created to build on these two protocols, making email authentication easier to manage and enforce.

Businesses of all sizes, government agencies, and anyone who wants to protect their email domain from unauthorized use implement DMARC.
By blocking or quarantining unauthenticated emails, DMARC prevents most phishing and impersonation attacks from reaching your organization’s recipients, helping to protect clients and stakeholders.
A DMARC record is a line of text added to your company’s DNS settings. It tells email servers how to handle unauthenticated messages and where to send reports about email activity.

Ready to protect your business?

Take the next step in securing your organization’s email domain by booking a personalized demo or starting a free trial today. Understanding DMARC can help your company prevent phishing, spoofing, and other email-based threats while improving deliverability and building trust with recipients.

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