I have an Exchange 5.5 installation on a Windows 2000 box with SP3, and I want to move approximately 1,500 mailboxes there from am Exchange 5.5 SP2 box on Windows NT 4.
What is the best way and do I need to upgrade the existing box to SP3 before moving the mailboxes?
We were considering just restoring the databases to the new server; is that a possibility?
The easiest way to do this will be to set up your new server as a member of the same site as the old one. Then you can simply select the mailboxes you want to move from the Recipients collection in Exchange Administrator and then click Tools > Move Mailbox.
If you can't put the new server in the same site, try using ExMerge from Microsoft. It'll essentially export all of the data from the old server mailboxes and then import all of that data into the new server mailboxes. Be forewarned, however, when you do this you're going to lose single-instance storage, so you may need a lot more disk space to store the same messages on the new system.