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.