# Validation Checklist

Status: Sanitized portfolio evidence
Scope: Mail flow post-change verification
Evidence type: Validation checklist

## Objective

Confirm that corrective action restored expected mail-flow behavior and did not introduce secondary symptoms.

## Technical Areas Demonstrated

- Post-change validation.
- Queue health review.
- Controlled test message verification.
- Stability observation window.
- Evidence capture for RCA closure.

## Issue Summary

This checklist captures the validation phase for a sanitized troubleshooting RCA scenario. No customer names, ticket numbers, IPs, or credentials are included.

## Scope

- Mail transport path.
- Queue behavior.
- Test-message delivery.

## Symptoms

- Delivery delay observed before remediation.
- Queue backlog present during triage.

## Impact

- Delayed delivery for a limited period.

## Timeline

- 09:44 UTC: Test message submitted.
- 10:03 UTC: Rule order correction applied in the test workflow.
- 10:18 UTC: Queue backlog began to drain.
- 10:41 UTC: Timing returned to normal.

## Triage Steps

- Reviewed queue state before the change.
- Confirmed the issue was isolated.
- Rechecked the same path after remediation.

## Root Cause

Transport rule precedence created an unnecessary delay in message processing.

## Corrective Actions

- Reordered the rules.
- Submitted a control message.
- Observed the recovery path.

## Validation Performed

- [x] Confirmed the control message delivered successfully.
- [x] Confirmed queue backlog was reducing.
- [x] Confirmed no new symptoms appeared during monitoring.
- [x] Confirmed normal timing returned within the verification window.

## Prevention Steps

- Keep this checklist with future transport changes.
- Review message queue behavior after rule updates.
- Record rollback and verification notes together.

## Lessons Learned

- Validation should prove both delivery and stability.
- A checklist keeps the recovery path repeatable.