Virtualization update - it's kinda supported - sorta

Exchange Server running on virtual machines has always been a somewhat uncomfortable topic for many Exchange Engineers.  Microsoft's support policies for VMware virtualized servers has always been confusing - to say the least - but with the advent of Hyper-V, their stance has softened significantly.  These days, the official line is that you can run Exchange Server 2007 SP1 on Hyper-V or any other Server Virtualization Validation Program (SVVP) -cleared virtualization product. In short, MSFT will now offer best-effort support for Exchange, even if it's running in a VM, with a few key exceptions.

First, the VM platform has to be part of the SVVP approved list.  There's only a few right now, but they're the major players. Hyper-V, ESX and Xen are all on the list, and for more info you can visit the SVVP site and click under "Products" to see who's been certified.

Also, you cannot be running the Unified Messaging role.  MSFT will still only support this role on physical servers, most likely due to the close interaction of the UM role with PBX and other phone systems.

Finally, you still need to be aware of this article from the MSFT knowledge base.  Even with the new best-effort support policies, MSFT may request that you try to re-create the problem either on physical servers or Hyper-V VM's, which could be a cumbersome process.

So, while MSFT is making great strides in extending support to virtualized Exchange servers, it may still be some time before complete support is available.  This isn't to say that you can't virtualize Exchange successfully, it's just that you definitely should look before you leap on this particular topic. Be sure to line up support resources from VMware, Citrix, or whomever produces your VM platform ahead of time. This way, if something goes awry, you know who to call for support - and in what order to make the calls.