Hi Preston,
You may want to take a look at the "Desktop Message Access" section of the following page on Cisco.com. Cisco Unity Express allows users to access their messages via a separate IMAP account, for playing, saving or deleting, but if you need to be able to use an email client for replying, forwarding, or recording new voicemail then I'd recommend going to Cisco Unity Connection version 8.5 (which runs on it's own server).
http://www.cisco.com/en/US/prod/collateral/voicesw/ps6789/ps5745/ps2237/product_data_sheet0900aecd806bfc37.html
Kind regards,
Craig