you just basically proved that you did not even look at the JavaMail faq for more than a few seconds.
The answer lies with Microsoft. If they don't provide an API to communicate with their products you're basically stuck. Since they have their own wonderful .NET technology I'm sure you're out of luck there where Java is concerned. Perhaps you can do something using COM through the JACOB project, but that is far from trivial stuff. You could search for third party efforts; you can Google for those ('java Microsoft exchange'). Good luck with that.