How can I use the Dropbox desktop app through the Intranet?

We use Dropbox through the Intranet, the host can not access the Internet, we need to open the normal use of Dropbox whitelist in the firewall, at present we only open www.Dropbox.com, but the software will show that the network connection is abnormal.

 If I want to use Dropbox, what other domains or IP addresses do I need to open up? Thank you.