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Exchange Online 550 5.4.1 — Recipient Address Rejected

Exchange Online rejected the recipient address, including cases where directory-based edge blocking identifies the address as invalid.

Diagnose your exact bounce Email Infrastructure Digital Twin

Most common causes

  • The recipient address does not exist in the destination directory
  • The address was removed or mistyped
  • The destination directory is not exposing the recipient to the inbound path

What to verify next

  1. Verify the full recipient address
  2. Confirm the recipient exists and is mail-enabled
  3. Check recent directory or routing changes if a previously valid address began failing

Best diagnostic path

Live analysis

Mail Failure Doctor

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

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 NDR 550 5.4.1 reference.