Right, so....
Need to get a report showing both Outlook 2010 and 2016(O365 install), connected PSTs...
Now it looks like there is a Registry value (see https://stackoverflow.com/questions/23800571/registry-key-to-find-pst-locations) which shows where PSTs are stored, and you can make queries of file locations via WMI (see here https://blogs.technet.microsoft.com/heyscriptingguy/2005/04/08/how-can-i-get-a-list-of-all-the-pst-files-on-a-computer/).
The upshot of this is to find out how many users are using PSTs on Network Shares (a BAD thing), and how much data is in there... ALSO to find out how many users are using local PSTS (ANOTHER BAD THING, but for a different reason)...
Anybody know how BEST to do this - I can see a kludge forming in my mind already (reg key to start, maybe), but....
Cheers all.
Argon0