Somebody correct me if I'm wrong...but here's my take on it.
A PST is indeed the only way to do it. I've found that the server Administrator can't even access the exchange directories of other users. The simplest way appears to me to be a PST archive of your Exchange mailbox. Setup the new account in Smartermail. Connect Outlook to Smartermail using IMAP. Import the PST pointing it at your IMAP Inbox. I'm sure not sure how the non-mail parts of the PST interact at that point... Anybody else? I wonder...would Outlook Sync do the trick here?
Chris