My client is running 4.0(3) with VM/Exchange, however they are interesting in UM via their existing Notes environment. By any chance is there any documentation related to migrating from an VM/Exchange to a UM/Domino scenario?
There is not going to be an easy way. If you want to use Domino as the backend, you will have to reinstall.
Unfortunately DiRT would not be an option - this is from the help file: "However you cannot restore a Domino system to an Exchange system or an Exchange system to a Domino system"
