Here is a simple Exchange Management Shell command that will move all of your Offline Address Books from the Exchange 2003 OAB generation server to an Exchange 2007 OAB generation server.
[PS] C:\>Get-OfflineAddressBook | Move-OfflineAddressBook -Server EXCH-2007 -confirm:$false WARNING: Do not turn off public folder publishing for offline address book (OAB) "\Default Offline Address List" before it is generated on the target server "EXCH-2007". If you turn off public folder publishing prematurely, the entire OAB will be downloaded for all users who are associated with this OAB.
