Plug-in and Corporate firewalls?

Plug-in and Corporate firewalls?

When I log into Zoho using the Excel Plug-in within my company, the shared applications don't show up in the box, only the sample "Welcome" application. Do company firewalls block these? Do I need a list of url's to give to my IT Manager to unblock them? We do use blocking software. I would rather have my users logging into Zoho through the Excel application as opposed to going through a web browser, which is slower and less functional than Excel.

Please help.

John