See http://mydsondemand.com/gettingstarted_exchange for some words and a diagram on how you can leverage MS Exchange messaging (via IMAP) into a mydigitalspace onDemand based application.
The diagram also shows a technique we are using to map business processes and functions to endpoints. The size of the circle relates to the importance of that endpoint within the customers application.
There are a lot of corporations with messaging information trapped within exchange servers - the mydigitalspace onDemand can extend the value considerable via it's 100% RESTful based application framework - only limited by the views of the information you can imagine.
Of course you can just as easily use IMAP/SSL to connect to GMail and achieve similar results with a utility level hosted service.