Since the CISCO Router is already configured for VPN, whenever you connect to VPN, you can go to outlook and you will have your mails downloaded as if u were on the network (of course, you should have the outlook settings done for connection to the Exchange Server).
A different solution would be to make Outlook available for web access (that is you access your mailbox from Internet Explorer, but since you have VPN, it's easier to access emails from outlook then from Internet Explorer.
