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Exchange Online NDR guide

Check 550 5.7.233 before changing a mail route

Exchange Online NDR 550 5.7.233 indicates that a non-trial tenant has exceeded its Tenant External Recipient Rate Limit. Confirm the live tenant state first, then attribute the senders and assign the remediation work.

Turn sender rows into an action plan

Five checks in order

  1. Preserve the evidence. Record the full NDR, affected sender, recipient pattern, tenant, and UTC timestamps.
  2. Open the tenant report. In the Exchange admin center, go to Reports, Mail flow, then Tenant Outbound External Recipients.
  3. Confirm live enforcement. If authorized, use Get-LimitsEnforcementStatus to check ObservedValue, Threshold, Verdict, and EnforcementEnabled.
  4. Attribute the volume. Use message trace data or Microsoft’s Get-TerrlExternalRecipientEstimate script to identify top senders and recipient domains.
  5. Assign the change. Name the business owner and technical owner, document the route to review, and define a test, rollback condition, and verification evidence.

Live status and attribution answer different questions

EvidenceAnswersDoes not answer
EAC report / Get-LimitsEnforcementStatusCurrent tenant threshold, observed value, verdict, and enforcement state.Who owns each sending source or how it should be remediated.
Message trace / support-script estimateWhich senders and recipient domains contribute to estimated volume.The authoritative live counter or the correct destination for a workload.
Owner-led action planWho will decide, implement, test, roll back, and verify each reviewed route.Microsoft’s live quota or guaranteed delivery.

Common questions

What does 550 5.7.233 mean?

Microsoft documents 550 5.7.233 as the NDR used when a non-trial tenant exceeds its Tenant External Recipient Rate Limit for the rolling 24-hour window.

Does the NDR identify the sender that consumed the quota?

No. The NDR identifies the tenant-level limit condition. Use the EAC report, message trace data, or Microsoft’s support script to attribute contributing senders.

Can sending resume immediately after a change?

Not necessarily. Microsoft says the rolling window may take minutes or up to 24 hours to fall below the limit, depending on the sending pattern.

Is the support-script estimate authoritative?

No. The estimate is for attribution. Get-LimitsEnforcementStatus is the live source for the current observed value, threshold, verdict, and enforcement state.

Should every high-volume source be moved?

No. Confirm the owner, purpose, eligibility, implementation responsibility, test, rollback, and post-change verification before approving any route.

Continue with the evidence

Prepare a sender CSV, then use the local analyzer to create a reviewable draft. SenderOwner does not change Exchange Online or an external delivery provider.

Sources