Recently the oft-referenced KB.810986 that talks about the support policy for clustering was refocused to encompass only the support policy for 3rd party cluster software (hence the updated title: “Microsoft support policy for Exchange Server installations that are running with a third-party Cluster service”).
But, if you’re a careful observer of the collection of Exchange clustering KBs, you may remember that KB.810986 is the KB article that has historically also provided the support stance regarding making nodes of an Exchange cluster into domain controllers. There was a single paragraph (a single sentence in a paragraph, really) that said something along the lines of “don’t make Exchange cluster nodes into domain controllers”.
Fear not! Rather than losing this (very important) support stance in the rewrite of KB.810986, it’s actually been expanded into its own dedicated KB article: KB.898634 (“Active Directory domain controllers are not supported as Exchange Server cluster nodes”).