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1 result for “550 5.4.1”

• Exchange Online NDR 550 5.4.1: Recipient address rejected: Access denied
  RESEARCHED · Confidence 65/100

  This NDR means Exchange Online's directory-based edge blocking rejected the message because no valid recipient object matches the SMTP address; the fix depends on the scenario, from a simple typo to a hybrid proxy-address resync.

  550 5.4.1