carrier_rejected

Do not hard-permanently remove on a single hit. Soft-suppress or require a second failure before permanent removal.

{
  "object": "event",
  "type": "message.failed",
  "livemode": true,
  "data": {
    "object": "message",
    "message_id": "msg_uuid",
    "status": "failed",
    "delivery_error_code": "carrier_rejected",
    "error_message": "The carrier rejected the destination for an ambiguous reason (deactivated, unable to receive, prepaid, or policy)."
  }
}