You must run this from a 32-bit Windows OS (I used Windows 7 Ent. 32-bit) with Exchange Management Tools installed, version Exchange 2007 SP1 or later, (I used Exchange 2007 SP3 with update rollup 13) and Outlook 2003 or Outlook 2007 (I used Outlook 2007 with SP3).
Start Exchange Management Shell (EMS) from the client that is member in the same domain as the exchange server. Your user account must be an Exchange Organization Admin or an Exchange Server Admin on the Exchange server who has the mailboxes you want to export.
Your account must have full mailbox access on the mailboxes you want to export.
Example. anna is the alias for the users mailbox you want to export. danieladmin is your account.
Run this command from EMS:
Add-MailboxPermission -Identity anna -User danieladmin -AccessRights FullAccess
To export annas mailbox:
Export-Mailbox -Identity anna -PSTFolderPath \\fileserver\PSTexport