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.
Best Answer
My suggestion would be to plan an upgrade to Exchange 2010 SP1 RU3. The SP1 removes the requirement to have outlook installed on the servers to import / export mailboxes.
Although, I do have Outlook 2010 x64 installed while trying to resolve the export to .pst issue. We have had no issues while it's been installed. We are moving to SP1 in the next week or so.