Why am I receiving so many DMARC reports?

DMARC reports are sent by various mailbox providers and mail servers that receive emails from your domain. If you're sending emails to users on different services or even different regional servers of the same service (like Google or Yahoo ), each distinct entity will send its own report, identified by a unique report_id . This is normal behavior.

How can I tell if multiple reports are duplicates or distinct?

You can determine if reports are truly identical by checking the report_id field within the XML content of each report. Each distinct report should have a unique ID. Additionally, the submitting domain (the receiving mail server) can usually be found in the email's subject line or filename. Different submitting domains indicate separate reports.

My DMARC report shows SPF 'fail' but DKIM 'pass.' What does this mean?

A spf=fail in the policy_evaluated section often means that while the SPF check itself passed, the domain in the Return-Path (or Mail From ) didn't align with your From header domain. DMARC only passes if either SPF or DKIM aligns. It does not mean a fundamental SPF authentication failure.

Is there a way to reduce the number of DMARC reports I receive?

To reduce the volume of DMARC reports, you can explore options like using a DMARC aggregate reporting service that processes the raw XML reports for you and provides a consolidated view. You could also carefully manage your rua tag to send reports to a dedicated mailbox or service, rather than your primary inbox. Some providers also offer options to specify a sample rate for reports.

How do I identify which receiving domain sent a specific DMARC report?

To determine the actual receiving domain that sent a DMARC report, check the email's subject line or the filename of the attached XML report. These typically include the name of the mail server or organization that generated the report. For example, a report might come from google.com , outlook.com , or yahoo.com .

Why am I receiving multiple DMARC reports from the same domain? - Troubleshooting - Email deliverability - Knowledge base

It can be quite startling to open your inbox and find it flooded with DMARC aggregate reports, especially if they all seem to be for the same domain you manage. You might wonder if something is broken, if your domain is under attack, or if you've misconfigured something critical. This common experience often leads to a bit of panic, but it's usually a sign of DMARC working as intended, albeit sometimes in unexpected ways.

DMARC aggregate reports provide crucial insights into your email ecosystem, detailing how your domain's emails are being authenticated (or failing to authenticate) across the internet. Each report summarizes the results from a specific receiving mail server over a 24-hour period. Understanding why you're receiving multiple reports from what appears to be the same domain is key to properly leveraging DMARC for your email security and deliverability.

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The mechanics of DMARC reporting

DMARC, or Domain-based Message Authentication, Reporting, and Conformance, is a powerful email authentication protocol designed to protect your domain from impersonation and phishing. For it to work effectively, mailbox providers that receive email claiming to be from your domain send back aggregate reports. These reports offer a high-level overview of email traffic, showing how many messages were sent, their authentication results (SPF and DKIM), and what policy was applied (none, quarantine, or reject).

Mailbox providers are configured to generate and send these aggregate reports periodically, typically once every 24 hours. This means that for every domain where you have a rua tag specified in your DMARC record, you can expect to receive daily reports from various mail servers across the internet. The volume of reports you receive depends on how much email your domain sends and how many different domains you send to.

It's important to understand that each individual mail server or organization that processes email from your domain and supports DMARC reporting will send its own distinct report. So, if your emails are reaching a wide array of recipients, each potentially using a different email provider, you'll receive a report from each of those providers.

Dissecting multiple reports from the same sender

The confusion about receiving multiple DMARC reports often stems from the reporting entity. While a report might come from, say, Google (or

Yahoo), it doesn't mean Google sent you 15 identical reports for the exact same set of emails. Instead, it indicates that different mail servers *under* that overarching organization (like various regional Google data centers or

Microsoft's different services) have each compiled and sent their own aggregate report.

Each valid DMARC aggregate report should have a unique report_id within its XML structure, as specified by the DMARC specification. If you're seeing different report_id values, you are indeed receiving distinct reports, even if they originate from what seems like the same large email service provider. These reports are often generated by different data centers or sub-systems within that provider's infrastructure.

Think of it this way: your domain sends email to a multitude of recipients, and these recipients use different mail services. While Gmail is one service, it might have servers in various locations. Each of these servers processes emails, and if configured to send DMARC reports, they'll each send one specific to the emails they processed from your domain. This also applies to mail services that forward email, as email forwarding can sometimes lead to unexpected DMARC report behavior.

Example DMARC aggregate report snippetxml

<?xml version="1.0"?>
<feedback>
  <report_metadata>
    <org_name>Yahoo</org_name>
    <email>dmarchelp@yahooinc.com</email>
    <report_id>1709343990.504071</report_id>
    <date_range>
      <begin>1709251200</begin>
      <end>1709337599</end>
    </date_range>
  </report_metadata>
  <policy_published>
    <domain>nobilzampa.com</domain>
    <adkim>s</adkim>
    <aspf>s</aspf>
    <p>reject</p>
    <pct>100</pct>
  </policy_published>
  <record>
    <row>
      <source_ip>149.72.146.168</source_ip>
      <count>1</count>
      <policy_evaluated>
        <disposition>none</disposition>
        <dkim>pass</dkim>
        <spf>fail</spf>
      </policy_evaluated>
    </row>
    <identifiers>
      <header_from>nobilzampa.com</header_from>
    </identifiers>
    <auth_results>
      <dkim>
        <domain>nobilzampa.com</domain>
        <selector>gh9</selector>
        <result>pass</result>
      </dkim>
      <dkim>
        <domain>sendgrid.info</domain>
        <selector>smtpapi</selector>
        <result>pass</result>
      </dkim>
      <spf>
        <domain>mailergh9.nobilzampa.com</domain>
        <result>pass</result>
      </spf>
    </auth_results>
  </record>
</feedback>

To identify these distinct reports, you should look at the report_id within the XML file and the submitter's domain, which is typically found in the email's subject line or filename. Different report_id values indicate separate reports. The table below illustrates how you might differentiate these reports:

Report ID (from XML)	Reporting Entity (from email subject/filename)
1709343990.504071	Yahoo.com
1709343990.504072	Google.com
1709343990.504073	Outlook.com (Microsoft)

Understanding authentication results and DMARC alignment

When you review DMARC reports, you might see spf or dkim results listed as fail within the policy_evaluated section, even if the individual SPF or DKIM checks passed. This is a crucial distinction and a common source of confusion.

The policy_evaluated section reports on DMARC alignment, not just the raw SPF or DKIM authentication result. For DMARC to pass, either SPF or DKIM (or both) must not only authenticate correctly but also align with the domain in the From header of the email (the one users see). This alignment check is what DMARC primarily enforces.

For instance, if SPF authenticates pass for your Return-Path domain but this domain doesn't match your From header domain, DMARC will report SPF as fail in the policy context, even if the raw SPF check succeeded. This is a key reason why you might be receiving DMARC failure reports when your authentication seems correct.

Understanding DMARC alignment

DMARC evaluates if the domain in the From header (the visible sender) aligns with the domains used for SPF or DKIM authentication. This alignment can be either relaxed (subdomains are okay) or strict (exact match required).

SPF alignment: The domain in the Return-Path (also known as Mail From) address must align with the From header domain.
DKIM alignment: The domain in the d= tag of the DKIM signature must align with the From header domain.

This aspect of DMARC reports is vital for interpreting your reports correctly. A spf=fail in the policy_evaluated section often means that SPF passed, but the domain used for SPF authentication didn't align with your From header. This is common when using third-party sending services that might use their own subdomain for the Return-Path.

Views from the trenches

Best practices

Always verify the report ID and submitting domain for each DMARC report to ensure it's a unique report.

Use a DMARC monitoring platform to automate the processing and analysis of large volumes of reports.

Regularly review your DMARC reports to identify legitimate sending sources and detect potential spoofing attempts.

Implement a DMARC policy with gradual enforcement, starting with 'p=none' to gather data before moving to 'quarantine' or 'reject'.

Common pitfalls

Assuming all reports from the same Mailbox Provider are duplicates without checking unique report IDs.

Misinterpreting an SPF 'fail' or DKIM 'fail' in DMARC reports as a fundamental authentication failure rather than an alignment issue.

Ignoring DMARC reports due to high volume, which can lead to missed insights into unauthorized sending.

Not configuring DMARC records with the correct 'rua' and 'ruf' tags to receive all necessary report types.

Expert tips

An expert from Email Geeks notes that multiple DMARC reports from the same domain typically mean they are from different receiving domains.

An expert from Email Geeks recommends checking the message ID and XML report ID to confirm if reports are truly identical.

An expert from Email Geeks advises that DMARC passes if either DKIM or SPF aligns with the header From domain, not necessarily both.

An expert from Email Geeks suggests that the subject of the reporting email and the filename contain the reporting domain (submitter) for verification.

Expert view

Expert from Email Geeks clarified that recipients send one report per domain, so if the same RUA is used for multiple domains, that will result in more reports.

2024-03-08 - Email Geeks

Expert view

Expert from Email Geeks suggested verifying if the Message-ID of the email or the report ID of the XML are identical across multiple messages to confirm if they are duplicates.

2024-03-08 - Email Geeks

Navigating your DMARC report volume

Receiving multiple DMARC reports from seemingly the same domain is a normal part of DMARC implementation and indicates that mailbox providers are actively monitoring your email traffic. While it might feel overwhelming at first, especially if you're not using a DMARC report analyzer, it's a sign that your DMARC setup is working.

The key is to differentiate between truly identical duplicate reports (which are rare and often indicate a processing error) and distinct reports from different receiving entities or sub-systems. Always check the unique report_id and the actual submitting domain (receiving domain) to understand the full scope of your email deliverability landscape.

Leveraging these reports properly is essential for maintaining a healthy sender reputation, ensuring your legitimate emails reach the inbox, and protecting your domain from phishing and spoofing. Don't be deterred by the volume, but embrace it as a valuable source of data for improving your email program. For effective management of your DMARC reports, consider utilizing a dedicated DMARC monitoring service that can parse, aggregate, and visualize this data for you, making it actionable and easy to understand.