I have Zimbra CS and Zimbra Desktop running satisfactorily on an Ubuntu Linux machine. When I have Zimbra Desktop running, I can use a browser at the same time to http://localhost:7633/desktop/login.jsp and get into my e-mails via a web interface.
However, when I do this from another PC on the same network, I get:
Unable to connect
Firefox can't establish a connection to the server at 192.168.0.131:7633.
I can go to another PC on the network and open an HTTP to the server (which also runs on the same Ubuntu box) and I can also use https: to get to the server's administration pages.
What's the reason here - I do not have a firewall on Ubuntu, at least not as far as I know!