We're running Exchange 2000 Enterprise edition on and Exchange 2000 server with sp4. We have one mailbox store in each of 4 storage groups. The mailbox store in the first storage group is getting to be rather large but we can't afford the downtime associated with an offline defrag. I want to move all of the mailboxes into other storage groups, delete the message store in the first storage group, create a new meassage store, and move some of the users back. Can I do this? Should I move the System and System Attendant mailboxes? I'd also appreciate any other caveats about deleting the first mailbox store.