I am looking into Zimbra Desktop as a replacement for our small company's e-mail client. Currently, all employees have a POP account with our ISP.
I'd like to investigate using the ZCS for all non-email tasks (calendar, contacts, etc.) but keeping the actual e-mail portion with the ISP. Since we don't have dedicated IT staff if there were issues with a locally hosted mail-server it could be quite catastrophic. Calendar and contact data, however, is not business critical.
Ultimately I think it would make sense to either go with a third party server host, or run our own server (i have succesfully installed and configured a Zimbra test server) but I would like to know if anyone else has experienced doing a staged transfer of services to ZCS.