How to do Root Cause Analysis in MS Admin Centre as Support Team said they are in break & fix support. My mails from external to internal were not working for 6 hours.

shyam s 0 Reputation points
2026-08-05T12:44:18.26+00:00

How to do Root Cause Analysis in MS Admin Centre as Support Team said they are in break & fix support. My mails from external to internal were not working for 6 hours.

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  1. Killian N 3,065 Reputation points Independent Advisor
    2026-08-05T14:36:44.6333333+00:00

    Hi shyam s,

    I understand the business impact of delayed or failed inbound email delivery. To perform a Root Cause Analysis for this type of Microsoft 365 mail-flow issue, need to review both Microsoft service-level information and tenant-level mail-flow evidence.

    Please note that Microsoft 365 Admin Center does not provide a single “Generate RCA” option for every mail-flow issue. A formal Microsoft RCA is usually available only when Microsoft confirms a service incident affecting Microsoft-managed services. If the cause is related to DNS, MX routing, mail-flow rules, connectors, third-party filtering, sender-side systems, or tenant configuration, the case is handled as a break/fix investigation.

    1. Check Microsoft 365 Service Health Go to https://admin.microsoft.com > Health > Service health and review Exchange Online for any active or historical incident during the affected time.
    2. Check Issue History In Service Health, check Issue history for the last 7 or 30 days. If there is a matching Exchange Online incident, record the incident ID, start time, end time, impact, and final update.
    3. Run Message Trace Go to https://admin.exchange.microsoft.com > Mail flow > Message trace. Run a trace using the affected external sender, internal recipient, date, time, time zone, subject, and message ID if available.
    4. Review Message Trace Result
      • Delivered: Check mailbox rules, Junk folder, Focused Inbox, forwarding, or retention settings.
      • Filtered/Quarantined: Check Defender quarantine, anti-spam, and anti-phishing policies.
      • Failed/Rejected: Check NDR, connectors, transport rules, accepted domains, SPF/DKIM/DMARC, and sender reputation.
      • Deferred/Delayed: Check retry attempts, connector status, and Service Health.
      • No trace found: Microsoft 365 may not have received the message. Check sender logs, MX records, DNS, or third-party gateway logs.
    5. Validate Mail-Flow Configuration Please confirm MX records, accepted domains, inbound connectors, mail-flow rules, anti-spam policies, and any third-party email security gateway were working correctly during the affected time.
    6. Collect RCA Evidence Please share the following details:
      • Issue start and end time with time zone
      • External sender address
      • Internal recipient address
      • Message subject and Message ID, if available
      • NDR or bounce message, if any
      • Message Trace result/export
      • Service Health incident ID, if any
      • Confirmation whether all external senders were affected or only specific domains
      • Third-party gateway logs, if applicable

    For more information, please refer to the following link:

    I hope this information is useful. Additionally, as other users have raised similar concerns and may not be aware of where to share their feedback, I hope this response helps clarify the situation and suggests a potential next step. Highlighting this information can make it more visible to others in the community who may be facing the same issue, making it easier for them to find guidance and contribute their feedback as well. 

    Thank you again for your time and for raising this important usability concern. If you have any further questions or need additional assistance, please don’t hesitate to reach out. 

    I look forward to your thoughts on this. 

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