Migrate unix email to Exchange?

I am planning on implementing MS Exchange at my company this coming summer. I currently use Unix email (sendmail,pine,Netscape Messenger)for an email system. I know that I will probably have to set up each account manually, but does anyone know how to migrate users folder to Exchange? For example, a unix user named Bob has a folder in his directory called Finance. How can I get Bob’s Finance folder to show up when Bob logs into his new Outlook client?