Reprinted upon request, here’s the Ed Crowley Exchange Server Move Method(tm). My method should create much less potential for grief, because you have practically zero downtime. You can perform all of the steps below at your own pace and in just about any order, and most, if not all, of them during working hours. What’s more, you can usually very easily back out any of the steps if things don’t go as expected. While not the easiest method, technically, it is certainly the least risky.
1. Bring up a new server as a new server in the same site with a different name of course.
2. Move the mailboxes using the Exchange Administrator. Move all at once, one at a time, or at some rate in between. In many cases, you can move the mailboxes during working hours because each user is affected only during the time his own mailbox is the one being moved.
3. Create replicas of the public folders on the new server. When the contents of the folders have replicated (do wait a little while!), remove the replicas from the old server.
4. Create new connectors on the new servers. Change the costs of the old connectors you’re replacing to be higher than the new ones, then recalculate routing. Create MX records pointing to the new IMS as appropriate, and change the cost on the old MX record so that it is higher than the new one. When you’ve checked and verified that messages are flowing across the New connectors, remove the old ones, then recalculate routing again.
5. Follow the steps in Q152959.
6. Leave the old server up for a time while MAPI clients connect to the new server automatically. It’s true! You don’t have to do anything to MAPI clients!
7. Notify POP3 and IMAP4 users of how to reconfigure their clients to point to the new server.
8. Stop the Exchange services, then remove the server from the site.