How can I turn off file submission upload to JotForm's servers?

I have a Dropbox integration with my forms and the submissions do not necessarily have to be uploaded to JotForm servers, and hence avoiding the need to login and clear submissions manually as soon as the limit is reached. How can I turn this off please?

You can not turn it off. The files first have to be sent to our server and after that, they are forwarded to your Dropbox account. 

However, if you do not want to store the data on your servers you can use Auto Delete Submission app, that will automatically delete your submissions, as soon as they are received. It uses JotForm webhooks so it is almost instant.

Auto Delete Submissions

Thanks!