At the time of writing this article according to the DropBox web site, the DropBox desktop tool does not support NTLM authentication. For this reason it is necessary to add a bypass rule to CensorNet's Filters -> Bypass Module.

To ensure that DropBox works through the proxy server, please add the following:

dropbox.com:80
dropbox.com:443

-- TimLloyd - 22 Jun 2010