How can I use DMARC to prevent spammers from using my domain?

Summary

DMARC is a crucial email authentication protocol that helps prevent spammers from using your domain. It works by allowing domain owners to specify how receiving mail servers should handle emails that fail authentication checks (SPF and DKIM). The common approach is to create a DMARC record in the DNS settings of the domain that specifies a policy: 'none' (monitor), 'quarantine' (mark as spam), or 'reject' (block). Monitoring DMARC reports is vital to identify both legitimate sending sources and unauthorized attempts to use your domain. Implementing a gradual approach, starting with monitoring ('p=none') and progressing towards stricter policies ('p=quarantine' then 'p=reject') is generally recommended to avoid blocking legitimate emails. It is crucial to ensure that SPF and DKIM are properly configured before implementing DMARC. DMARC ultimately protects brand reputation, improves email deliverability, and enhances overall email security by limiting spoofing and phishing attacks.

Key findings

  • Domain Protection: DMARC protects your domain's reputation by controlling who can send emails using your domain and preventing malicious actors.
  • Authentication Policies: DMARC allows you to define policies (none, quarantine, reject) for handling unauthenticated emails.
  • Visibility & Security: Implementing DMARC improves visibility into email traffic, enables enforcement of anti-spoofing policies, and enhances email security.
  • DMARC Setup: DMARC allows domain owners to specify how email receivers should handle unauthenticated email purporting to be from their domain.
  • Brand Reputation: Without DMARC spammers can send email that appears to be coming from your domain, damaging your reputation, deliverability and customer trust.

Key considerations

  • Reporting Tools: Use a reporting tool to ensure all sources are aligned and passing authentication checks before enforcing a 'reject' policy.
  • Gradual Implementation: Implement DMARC gradually, beginning with a 'monitor' policy to understand legitimate email sources.
  • DMARC Monitoring: Continuously monitor DMARC reports to optimize email authentication and promptly identify potential threats.
  • SPF/DKIM Dependency: DMARC requires properly configured SPF and DKIM records; these protocols must be set up first.
  • Uncontrolled Servers: You cannot prevent emails from being sent on your behalf from uncontrolled servers, but DMARC can prevent them from being received.

What email marketers say
15Marketer opinions

DMARC (Domain-based Message Authentication, Reporting, and Conformance) is a crucial email authentication protocol that helps prevent spammers from using your domain. By implementing DMARC, you can instruct recipient servers on how to handle emails that fail authentication checks (SPF and DKIM). This includes options to monitor, quarantine, or reject unauthenticated emails, effectively protecting your domain's reputation and improving email deliverability. Monitoring DMARC reports is essential for identifying legitimate sending sources and unauthorized attempts to use your domain. A gradual implementation, starting with monitoring ('p=none') and progressing to stricter policies ('p=quarantine' then 'p=reject'), is recommended to avoid blocking legitimate emails.

Key opinions

  • DMARC Protection: DMARC protects your domain's reputation by giving you control over who can send emails using your domain.
  • Policy Enforcement: DMARC allows you to specify policies for handling unauthenticated emails: monitor, quarantine, or reject.
  • Visibility: DMARC provides visibility into who is sending emails on behalf of your domain, helping identify spoofing attempts.
  • Email Security: Improves email security by enforcing policies that prevent spoofing and phishing attacks.
  • Reduces Impersonation: Configured DMARC, SPF, and DKIM can significantly reduce the chance of spammers impersonating your domain.
  • Authentication Protocol: Without DMARC spammers can send email that appears to be coming from your domain, damaging your reputation, deliverability and customer trust.
  • Sender Reputation: DMARC improves sender reputation and deliverability, thus boosting trust with mailbox providers and recipients.

Key considerations

  • Reporting Tool: Use a reporting tool to ensure all email sources are aligned and passing authentication before changing DMARC policy to 'reject'.
  • SPF & DKIM: Implement SPF and DKIM correctly before setting up DMARC. If SPF and DKIM are not setup then DMARC will not work.
  • Gradual Rollout: Implement DMARC gradually, starting with 'p=none' to monitor and identify legitimate senders before enforcing stricter policies.
  • DMARC Reports: Continuously monitor and analyze DMARC reports to optimize email authentication and maintain a strong security posture.
  • Reject Doesn't Stop Attempts: Setting p=reject won't stop spoofing attempts, but it will prevent unauthenticated emails from being delivered.
  • Reputation Damages: Without DMARC your domain can be impersonated and this damages your reputation, deliverability and customer trust.
Marketer view

Email marketer from Email Geeks advises to use a reporting tool to ensure all sources are aligned and passing before changing the DMARC policy to 'reject'. He emphasizes the importance of aligning the return-path with the friendly from and DKIM signing with the correct key.

February 2023 - Email Geeks
Marketer view

Email marketer from Email Geeks explains that setting p=reject instructs mailbox providers to reject unauthenticated emails using your domain, but it doesn't stop spoofing attempts. He suggests that blocking the IP address of the spoofer is limited to inbound mail on controlled servers.

August 2024 - Email Geeks
Marketer view

Email marketer from ZeroBounce shares that DMARC monitoring is a crucial aspect of implementing DMARC. By setting up and regularly reviewing DMARC reports, you can gain insights into how your domain is being used, identify potential spoofing attempts, and adjust your DMARC policy to effectively protect your domain.

September 2024 - ZeroBounce
Marketer view

Email marketer from Email Marketing Forum recommends starting with a DMARC policy of 'quarantine' before moving to 'reject'. This allows you to monitor how email providers are handling your email and identify any legitimate sending sources that are failing authentication without immediately blocking them.

February 2022 - Email Marketing Forum
Marketer view

Email marketer from Reddit explains that properly configured DMARC, SPF, and DKIM can significantly reduce the chance of spammers impersonating your domain. The user stresses the importance of monitoring DMARC reports to identify any unauthorized sending sources and adjusting the policy accordingly.

July 2024 - Reddit
Marketer view

Email marketer from Sendinblue answers that DMARC is email authentication protocol, and without it, spammers can send email that appear to be coming from your domain. This damages your reputation, deliverability and customer trust. Implementing DMARC is essential to protect the reputation of the sender domain.

July 2023 - Sendinblue
Marketer view

Email marketer from Proofpoint explains how DMARC improves email security. Implementing DMARC provides visibility into who is sending emails on behalf of your domain and allows you to enforce policies that prevent spoofing and phishing attacks. It also mentions that continuous monitoring and analysis of DMARC reports are essential for optimizing email authentication and maintaining a strong security posture.

October 2021 - Proofpoint
Marketer view

Email marketer from Email Geeks details that DMARC aggregate reports contain data about the RFC5322.From header, including properly authenticated mail, unauthenticated mail, and spoofing attempts. He mentions that spoofed mail should fail authentication but could pass due to overly permissive SPF records or DKIM replay.

January 2025 - Email Geeks
Marketer view

Email marketer from Email Geeks agrees with Todd Herr, stating that you cannot prevent emails from being sent on your behalf from uncontrolled servers, but DMARC can prevent them from being received.

August 2022 - Email Geeks
Marketer view

Email marketer from Mailjet shares that DMARC protects your domain's reputation. By implementing DMARC, you can gain control over who is sending emails using your domain, preventing malicious actors from damaging your brand. Mailjet emphasizes that DMARC helps increase email deliverability rates by ensuring that legitimate emails are properly authenticated.

March 2025 - Mailjet
Marketer view

Email marketer from EmailToolTester explains that DMARC's best practice should be a gradual implementation strategy to monitor email traffic. By doing this you are ensuring legitimate emails are not being rejected, and also helping prevent malicious senders from damaging your brand.

October 2023 - EmailToolTester
Marketer view

Email marketer from EasyDMARC details the steps to implement DMARC, starting with setting up SPF and DKIM, then monitoring DMARC reports with a 'p=none' policy to identify legitimate sending sources. They recommend gradually moving to 'p=quarantine' and finally 'p=reject' once you're confident that all legitimate emails are properly authenticated, thus effectively preventing spammers from using your domain.

March 2021 - EasyDMARC
Marketer view

Email marketer from SparkPost shares that DMARC lets you specify policies for handling unauthenticated email, such as 'none' (monitor), 'quarantine' (mark as spam), or 'reject' (block). Setting a DMARC policy allows you to prevent spammers from using your domain by instructing receiving servers to reject unauthorized emails, protecting your domain's reputation.

February 2022 - SparkPost
Marketer view

Email marketer from GlockApps shares that DMARC is crucial for improving sender reputation and deliverability. Properly configured DMARC policies help ensure that your legitimate emails reach the inbox while preventing spammers from using your domain, thus boosting trust with mailbox providers and recipients.

August 2022 - GlockApps
Marketer view

Email marketer from Email Geeks shares information about DMARC aggregate reports being sent as individual XML sheets daily and suggests using a service to make sense of the data. He mentions the objective of ensuring all legitimate senders pass DMARC before enforcing a 'p=reject' policy and touches on inbound enforcement considerations.

January 2024 - Email Geeks

What the experts say
2Expert opinions

DMARC is an email authentication method used to protect your brand's domain from being spoofed in email attacks. Implementing DMARC involves setting a policy, such as 'reject', which instructs recipient servers to refuse emails that fail authentication. You need to monitor the emails, start in monitoring mode, and then advance to stricter protocols. DMARC requires careful setup and monitoring to avoid blocking legitimate mail while effectively preventing spammers from using your domain.

Key opinions

  • DMARC Protection: DMARC protects your brand from email spoofing and phishing attacks.
  • Control over Authentication: It allows you to control how recipient servers handle unauthenticated email claiming to be from your domain.
  • Reject Policy: Setting the DMARC policy to 'reject' instructs recipient servers to refuse emails failing authentication checks.

Key considerations

  • Careful Setup: DMARC requires careful setup and monitoring to avoid blocking legitimate mail.
  • Monitoring Mode: Start in monitoring mode before advancing to stricter protocols to understand your email traffic.
Expert view

Expert from Word to the Wise shares that implementing DMARC allows you to protect your brand from email spoofing and phishing attacks by controlling how recipient servers handle unauthenticated email claiming to be from your domain. The expert also says that you need to monitor the emails, start in monitoring mode, and then advance to stricter protocols.

June 2023 - Word to the Wise
Expert view

Expert from Spam Resource explains that you can set the DMARC policy to 'reject', instructing recipient servers to refuse any email that fails authentication checks. This prevents spammers from successfully spoofing your domain, but requires careful setup and monitoring to avoid blocking legitimate mail.

August 2022 - Spam Resource

What the documentation says
5Technical articles

DMARC (Domain-based Message Authentication, Reporting, and Conformance) empowers domain owners to instruct receiving mail servers on how to handle messages that fail SPF and DKIM authentication checks. By creating a DMARC record in your DNS, you specify whether to reject or quarantine unauthenticated emails. Implementing DMARC effectively prevents spoofing and phishing attacks by clarifying how email receivers should handle these failures, significantly reducing the effectiveness of spoofing attacks. Before implementing DMARC, ensure SPF and DKIM are properly set up, as DMARC builds upon these protocols.

Key findings

  • Domain Control: DMARC allows domain owners to specify how email receivers should handle unauthenticated email purporting to be from their domain.
  • SPF/DKIM Dependent: DMARC builds upon SPF and DKIM; proper setup of these is crucial.
  • Anti-Spoofing: DMARC prevents spoofing and phishing by allowing organizations to specify what happens to messages that fail SPF or DKIM checks.
  • DNS Record: Creating and publishing a DMARC record to your domain's DNS records is the first step.

Key considerations

  • Existing SPF/DKIM: Before implementing DMARC, ensure that SPF and DKIM are correctly configured for your domain.
  • Reporting Importance: Monitoring DMARC reports is important to identify and address any legitimate sending sources that are not properly authenticating.
  • Authentication Handling: DMARC tells receiving mail servers what to do with messages that fail authentication checks (SPF and DKIM), either reject them or mark them as spam.
Technical article

Documentation from RFC Editor (RFC7489) specifies that DMARC (Domain-based Message Authentication, Reporting, and Conformance) is designed to allow domain owners to indicate that their messages are protected by SPF and/or DKIM, and to give instructions if neither of those authentication mechanisms pass. DMARC defines how email receivers should handle failures, thus preventing spammers from using the domain.

August 2022 - RFC Editor
Technical article

Documentation from DMARC.org details how DMARC allows domain owners to specify how email receivers should handle unauthenticated email purporting to be from their domain. It clarifies that by publishing a DMARC policy, you can instruct receivers to quarantine or reject messages that fail authentication, significantly reducing the effectiveness of spoofing attacks.

January 2025 - DMARC.org
Technical article

Documentation from Agari by HelpSystems explains that DMARC builds upon SPF and DKIM. You should first make sure that these other two protocols are properly setup, so the domain's email is secure and is correctly validated. Implementing DMARC provides the visibility and the steps needed to make sure the emails are correctly authenticated.

April 2022 - Agari by HelpSystems
Technical article

Documentation from Google Workspace Admin Help explains that creating a DMARC record and publishing it to your domain's DNS records will help receiving servers handle messages from your domain. It outlines the importance of DMARC in telling receiving mail servers what to do with messages that fail authentication checks (SPF and DKIM), either reject them or mark them as spam.

October 2022 - Google Workspace Admin Help
Technical article

Documentation from Microsoft Learn explains how to use DMARC with Microsoft 365. Implementing DMARC helps prevent spoofing and phishing by allowing organizations to specify what happens to messages that fail SPF or DKIM checks. It also emphasizes the importance of monitoring DMARC reports to identify and address any legitimate sending sources that are not properly authenticating.

October 2023 - Microsoft Learn