Question:

The Unidentified Senders CSV report I downloaded is blank. But I see data in the UI under the Unidentified Senders section in the Authentication Reports on the 2nd tab called Known Forwarders. Why is the downloaded report blank?

Answer:

The reason why the CSV file with the report is empty is because the CSV file will only contain information present in the Unidentified IP Addresses tab. If there is no information under the Unidentified IP Addresses tab in Mostly Passing, Partially Passing, and Mostly Failing IPs, the CSV file will be blank.

In cases like the above, the information was in the tabs named Known Forwarders or Possible Senders. The exportable CSV report covers only the first Unidentified IP Addresses tab.