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exchange-online error

Exchange Online 550 5.7.64 — TenantAttribution Relay Access Denied

Exchange Online could not attribute the relayed message to the expected tenant because the inbound connector path no longer matched the configured identity or network conditions.

Diagnose your exact bounce Email Dependency Discovery

Most common causes

  • The on-premises or gateway source IP changed
  • Connector certificate identity no longer matches the configured path
  • Mail was routed through a different gateway than the connector expects
  • Hybrid or relay configuration changed without a corresponding connector update

What to verify next

  1. Map the message route and identify the actual connecting host
  2. Compare current source IP and certificate identity with the connector design
  3. Review recent gateway, NAT or routing changes
  4. Retest through the intended connector path after configuration is aligned

Best diagnostic path

Live analysis

Mail Failure Doctor

Classify the complete rejection and preserve provider-specific diagnostic context.

Open analysis → Live analysis

Email Dependency Discovery

Map applications and devices that depend on a relay or submission path before changing it.

Open analysis → Live analysis

Email Infrastructure Digital Twin

Map the domain’s public mail infrastructure and provider relationships before remediation.

Open analysis →

Why the exact message matters

The same status family can be triggered by different conditions, and providers frequently add diagnostic text that narrows the issue. Use the complete rejection text rather than treating the numeric code as a complete diagnosis.

Provider reference

For the provider-defined meaning and current requirements, review Microsoft Exchange Online NDR reference.