There are issues with the Top Internet Senders and Receivers by Message report because it was reporting public folders in v4.3 and now in v5 it is not.
This change was by design with removing Public Folders from the Top Senders/Receivers Report. The goal of v5.0 is to have these reports only show Mailboxes. A feature request has been logged for a Top Senders/ Receivers Report for Public Folders.
CR#96069
