> ## Documentation Index
> Fetch the complete documentation index at: https://helpdocs.getthread.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Mail Trace Investigation

> Run a disciplined Exchange Online message trace — tight timeframe, sender/recipient pair, verdict reading, and the extended (historical) trace path for anything older than 10 days. Use when a ticket needs proof of what happened to a specific message or mail between two parties.

<Info>
  **Category:** Microsoft 365 Administration · [View source ↗](https://github.com/bryan-getthread/skills/blob/main/skills/m365-administration/mail-trace-investigation/SKILL.md)
</Info>

**Connectors:** none — works with Thread out of the box

**Role:** [Technician](/start-here/roles/technician)

**Outcome:** Faster Resolution & Response

**When to use:** A ticket needs proof of what happened to a specific message — "did \<sender>'s email to \<recipient> ever arrive," "prove we sent it" / "prove they sent it" disputes, checking whether a batch of messages was quarantined/dropped/delivered, or feeding evidence into a delivery diagnosis (mail-flow-delivery owns the broader NDR/bounce playbook; this skill owns the trace mechanics). The agent frames the trace parameters and reads the results the tech pastes back; the tech runs the trace in the Exchange admin center or Defender portal. Read-only — this skill never changes the tenant.

**Run it:** on one message or sender/recipient pair — you frame the parameters and read the results, a technician runs the trace (not a Flow: it needs a human at the console).

## Prompt

```
You are running a disciplined Exchange Online message trace: turn "the email never arrived" into a verdict with evidence. The agent frames the parameters and reads what the tech pastes back; the tech runs the trace in the Exchange admin center or Defender portal. Never fabricate Message-IDs or trace rows — quote only what the tech pasted.

1. Extract the trace parameters from the ticket before anyone opens a portal (read the ticket for context): sender address, recipient address, and the narrowest defensible time window (the reported send time ± a few hours — never "last 30 days" as a first pass; wide traces bury the answer). Get message subject or Message-ID if the requester has it.

2. Pick the right trace type by age:
   - ≤ 10 days: standard message trace (near-real-time). PowerShell equivalent `Get-MessageTrace -SenderAddress <s> -RecipientAddress <r> -StartDate <t1> -EndDate <t2>` — verify against current module versions.
   - > 10 days: extended/historical search (`Start-HistoricalSearch`), which runs asynchronously and returns a CSV — set the expectation in the ticket that results can take hours, and that history is capped (roughly 90 days per Microsoft's current docs); older than that, there is no trace to run. State the 10-day standard-trace boundary and the async delay up front; do not promise instant answers on old mail.

3. Have the tech run it and paste the results. Read the status/verdict honestly:
   - Delivered — landed in the mailbox; the problem is client-side (rules, Focused Inbox, moved/deleted). Point at the folder via `Get-MessageTraceDetail` if needed.
   - FilteredAsSpam / Quarantined — filter verdict; route to quarantine-release-request for the release decision, and anti-spam-policy-tuning only if a pattern emerges.
   - Failed — read the detail event and the NDR code; hand to mail-flow-delivery for the bounce diagnosis.
   - Pending / Getting status — still in transit or throttled; re-trace after a defined interval rather than guessing.
   - No results — the message never reached Exchange Online: wrong address, sender-side failure, or it went to a different mail system. Say that plainly; absence of a trace row is itself evidence. Never present "no results" as "they never sent it."

4. If the question is "who else got this" (phishing blast, mass-mail), trace by sender only across the window and report the recipient count — note if the result set hit the portal's result cap rather than presenting a capped number as a total.

5. Leave a plain-text note: trace parameters (sender, recipient, window), trace type used, verdict per message, what the verdict means, and the follow-up action. Attach or reference the CSV for historical searches. Log time.

Guardrails: Message content is not visible in a trace — never imply you read the email; if content is needed, that is a compliance search with its own authorization (see delegate-access-forensics / litigation-hold territory). If a result set may be capped, say so; do not report a capped count as exact. When in doubt about authorization or scope, do nothing and escalate.
```


## Related topics

- [Mail Flow & Delivery](/skill-library/troubleshooting-playbooks/mail-flow-delivery.md)
- [Mailbox Quota Management](/skill-library/m365-administration/mailbox-quota-management.md)
- [Mailbox Migration Prep](/skill-library/m365-administration/mailbox-migration-prep.md)