When running the Inventory | Distribution Lists Report and adding the 'Allowed Senders' or 'Denied Senders' Column you will notice that the information is incomplete or empty. You will further notice that only user objects are being shown not Security or Distribution Groups.
Also, you may find that Allowed Senders or Denied Senders in Empty
The MessageStats Gathering only looks at the authOrig attribute which stores users that are allowed or denied sending messages to the Distribution List. It does not gather the DdLMemSubmitPerms, this attribute stores the Distribution and Security Groups allowed or denied sending to this Distribution List.
When the Everyone group is set to Allowed Senders for the Distribution List, this Attribute is <not set> ,this results in no value being passed to MessageStats and therefore empty columns in the report.
Waiting for Fix in a future release of MessageStats