It is not possible to use the Import-Mailbox or Export-Mailbox cmdlets unless Outlook 2010 x64 is installed on the Exchange server against which you try to run the command.
Does anyone have Outlook installed on their Exchange box? Are you aware of any issues or problems this might present? Are there any other cmdlets that require Outlook, or any other compelling reasons to install it on your Exchange server?
I've searched for Microsoft documentation or recommendations but can't find any.
EDIT: I'm trying to export to and import from PST files, not to another target mailbox.