David Passell sends some links to info about file sync. https://www.dropboxatwork.com/2014/05/what-is-file-sync/#.U6OElyVai9Y.email
Then there's this additional . . . "this was sent via http://addthis.com. Please note that AddThis does not verify email addresses." And then, "make sharing easier with the AddThis Toolbar:http://www.addthis.com/go/toolbar-em And finally, "To stop receiving any emails from AddThis, please visit: http://www.addthis.com/privacy/email-opt-out?e=ROQqiz.dD4wggiKcP4oqi2GBKps