Microsoft recently announced that Exchange Server 2007 wouldn't be supported on Windows Server 2008 R2. This decision has generated a bit of controversy, with Exchange administrators asking why a still-current product isn't being supported on a brand-new OS. In an attempt to clarify its reasoning, the Exchange product team posted an explanation on the Microsoft Exchange Team Blog that boiled down to two points:

  • Exchange 2007 SP2 was in development before the Server 2008 R2 release cycle, so SP2 would have been "delayed significantly" if it had to be tested against R2
  • Microsoft doesn't support upgrading the OS of an existing Exchange installation, and they don't plan to change this stance. They say that customer feedback indicates that the big need relative to Server 2008 R2 is to support R2 domain controllers, which Exchange 2007 SP2 does.

These points seem reasonable. After all, the product group is nearly done with a huge revision to Exchange in the form of Exchange Server 2010. Diverting testing and engineering resources to make sure that Exchange 2007 runs on a not-yet-released OS (remember, R2's street date is October 22) that you can't upgrade to in-place anyway doesn't make much sense.

However, I think there's another reason it makes sense not to support R2 with Exchange 2007: What would we actually gain?

Take a look at Microsoft's list of the top 10 reasons to upgrade to Server 2008 R2 and you'll see what I mean. Reduced desktop costs? Ubiquitous remote access? Although these features are no doubt useful (and some, like DirectAccess, are technically sweet as well), they have nothing to do with Exchange. Improvements to R2's Hyper-V implementation would benefit Exchange deployments, but to take advantage of them you'd have to be running your Exchange organization in a VM anyway, not directly on the host OS, so that point is moot too.

This isn't to say that R2 doesn't have other interesting reasons for a potential upgrade. For example, the Active Directory (AD) Recycle Bin is a neat concept that I think could be very useful in large-scale Exchange deployments, and the aforementioned DirectAccess (along with the new BranchCache system) is a terrific enhancement for distributed networks. However, there's just not much in R2 that directly benefits Exchange 2010, much less Exchange 2007, so I think the decision to put engineering resources into new development, rather than sustaining engineering support for running Exchange 2007 SP2 on R2, is further validated.

Having said that, it will be really interesting to see what the prevalent combination of OSs and Exchange versions will be a year from now. There's clearly a strong wave of pent-up demand for Exchange 2010 from companies that are on Exchange 2003 and are skipping Exchange 2007 altogether, but how will that translate into OS deployments? We'll have to wait to find out, but I'm betting that Server 2008 isn't ready to ride off into the sunset just yet.