Run a Web search for GAL Sync and you will find a plethora of commercial tools made to do the job. Before you plunk down a giant wad of cash, consider doing it yourself with a little PowerShell know how.
Dropbox and Onedrive Blocked? Use Exchange Server as a Secure File Mover
Unfortunately, blocking the services most suited for transferring data between branch offices, clients, or customer’s companies doesn’t remove the need to do so.
