So I have been working with Exchange 2007 and it has a lot of advancements over previous versions. One thing that I feel it is missing is in the area of Unified Messaging. It can interact with a few PBXes and IP PBXs out of the box, and a few motivated people have been able to use sipX as a Sip Proxy to pass the traffic from an asterisk server to the Exchange server. It is actually really simple if you follow these instructions by Ryan Newington. It is a bit older, and some things you have to guess at because they have changed, such as trixbox configurations and layouts, but over all you can swap out trixbox for other asterisk distributions, just remember to RTFM.  It does help to have a familiar with Linux in general, there is a lot done on this with Red Hat distros, such as Fedora or CentOS. I had some interesting issues trying to get the trixbox virtual machine running, such as I had to re-install GRUB, and use VMWare Converter (thanks Kobold) to convert the machine image from an ESX image to a VMware Server image. At the moment though, my system is stuck at the authentication stage from one server to the sipX proxy. I can call from the trixbox to the exchange server, but I can not call from the outside to the exchange server. I will try to work this out tomorrow.

I am tired and starting to ramble so I will just leave it at this for tonight.