Export or Import to PST Requirements
In addition to Export-Mailbox, Exchange Server 2007 SP1 also introduces new Import-Mailbox cmdlet to import mailbox data from a .pst file to a mailbox.
In order to export or import mailboxes to PST files the following requirements must be met:
Export or import to PST must be run from a 32-bit client computer with Exchange Management Tools installed (Exchange 2007 SP1 or later versions). The 32-bit requirement comes from a dependency with the Outlook client.
Either Outlook 2003 or Outlook 2007 must be installed on the client computer.
The user running the task must be an Exchange Organization Administrator or an Exchange Server Administrator on the server where the mailbox to export or import lives.