The following diagram shows how Celoxis fits in to your intranet.
A few things to note:
Uploaded files are stored on the disk and not in the database.
Database server and email server can be on the same machine or on a different machine.
If configured correctly, Celoxis can be accessed from your intranet as well as the Internet. To stop access to Celoxis from the Internet, configure your firewall appropriately.