Microsoft released an interesting tool to discover pst on remote Pcs and published with GPO.
In precedent blog post we mentioned implementation that I did with .vbs and .cmd that collect, with GPO, local pst and they are backup up with hobobcopy and robocopy.
http://www.alessandromazzanti.com/2015/09/backups-how-to-backup-remote-clients.html
Microsoft Exchange PST Capture 2.0 is used to discover and import .pst files into Exchange Server or Exchange Online.
https://www.microsoft.com/en-us/download/details.aspx?id=36789
In any case this article well explain tool usage and implementation:
http://msexchangeguru.com/2016/01/29/pst-capture-walk-through/