With the release somewhere on the horizon, it would be a good time to discuss the prerequisites for deployment. Those companies who are planning to be early adopters are probably already well aware of the list of requirements in order to launch it successfully.
There are two main categories of requirements for the new system. Active directory and the ones needed for Exchange itself.
For the active directory part, all the domain controllers in the organization will need to run 64 bit versions of Windows, preferably Server 2003 SP2 and above. If you use a forest, that should also be at least the same level. Exchange will only work with 64 bit architecture and has been built from the ground up to only use it. This may mean operating system upgrades before you even open the Exchange package.
The Exchange site of the migration also has its own prerequisites. The entire platform must be at a level higher than Exchange 2003 SP2. If they are running Exchange 2007, that also must have Service Pack 2 installed to work properly.
To transition effectively to Exchange 2010 it is best to build the new infrastructure beside the existing one. It is also best to start at the internet facing side, with a Client Access Server (CAS). To use Exchange 2010 you need to build new CAS servers, you can’t upgrade existing ones. The new CAS has to live alongside the existing one while the business still has mailboxes on the old system. The old CAS can be retired once the migration has completed.
To get them working, the certificate has to be propagated from the old CAS to the new one, then a new one has to be acquired for the new on and shared with the old. This will allow mail to be redirected between the two CAS servers depending on where the destination mailbox is housed. If a client connected to the Exchange 2010 CAS contacts a mailbox on the old CAS, the new CAS will redirect the data to the old to complete the transaction, and vice versa.
Next the new mailbox servers should be built and configured to sit alongside the legacy ones. Both servers will need to be running in order to move mailboxes between them. Once the mailbox transition is complete, the old mailbox server can be retired. Fortunately this once laborious task can now be automated with the new Online Move Mailbox tool. This process means the absolute minimum downtime for users as the data is replicated between servers and the active directory replication takes place.
The only server you can really replace at the outset is the edge server. Once you have subscribed it to the Exchange 2010 Hub Server it should work normally.
This is only an overview of what it to be a time consuming and complicated migration process. Proper planning should always be done before even removing the wrapping from the new hardware.

