I tried using Box for a similar reason (I needed a way to securely share multiple files and/or folders with external clients in a way that did not require them to install software or sign-up for some service) and it just doesn't work. I also desired a way to automatically upload new content to this platoform.

No dice. After emailing with 6 different Box employees (all ignoring my requests and trying to sell me on shit I didn't ask for, then would just pass me onto someone else) I was finally told that I could only do that if I paid for an enterprise "call for pricing" license.

Sigh. I'm using a http-auth secured index-of directory for now. If anyone has a superior suggestion, I'm all ears.