Microsoft weights sender reputation via SNDS and JMRP, and rejects unauthenticated bulk mail to consumer Outlook.com addresses.
What DMARC aggregate reports are#
DMARC aggregate (RUA) reports are daily XML files sent by mailbox providers listing, per sending IP, how many messages claimed your domain and whether they passed SPF, DKIM, and alignment. Forensic (RUF) reports contain samples of individual failures.
Why it matters#
Reports are the only way to see who is sending as your domain, including vendors you forgot and attackers you never knew about. Moving to p=reject safely depends on reading them.
Setting up DMARC aggregate reports for Outlook and Microsoft 365#
- Publish rua=mailto: pointing to a dedicated mailbox or a report processor.
- Collect reports for at least two weeks before drawing conclusions.
- Group sources by IP owner and match each to a known vendor.
- Fix alignment for legitimate sources; treat unknown high-volume sources as spoofing.
- Track pass rate weekly and tighten policy as it approaches 100%.
<record>
<row><source_ip>203.0.113.10</source_ip><count>412</count>
<policy_evaluated><disposition>none</disposition><dkim>pass</dkim><spf>fail</spf></policy_evaluated></row>
<identifiers><header_from>example.com</header_from></identifiers>
</record>How Outlook and Microsoft 365 reports results#
Open a delivered test message in Outlook and Microsoft 365 and view the original or headers. Look for Authentication-Results and any provider-specific verdict headers. Use the provider's sender dashboard for aggregate reputation.
Common mistakes#
- Reading raw XML by hand and giving up after day two.
- Ignoring low-volume unknown sources that turn out to be your own systems.
- Expecting RUF reports; most large providers no longer send them.
Frequently asked questions#
How do I read a DMARC report?
Each record lists a source IP, message count, SPF and DKIM results, and alignment. Use an analyzer to aggregate by source; the goal is to name every IP range.
Why do I see mail from IPs I do not recognize?
Common causes are forwarding, a vendor you forgot, an employee's personal tool, or spoofing. Volume and geography usually tell them apart.
Does Outlook and Microsoft 365 require DMARC aggregate reports?
Microsoft weights sender reputation via SNDS and JMRP, and rejects unauthenticated bulk mail to consumer Outlook.com addresses. Treat DMARC aggregate reports as required for any meaningful volume.