Exchange/Outlook through the Internet

I would just like to confirm if I can connect my microsoft outlook 2000 to my exchange server at the office through TCP/IP.
our users would like to connect to the internet anywhere in the world and then be able to access their email using outlook/exchange without any dialin or vpn to the server.
I heard it is possible by making some port settings..I would be grateful if someone could confirm it for me with details on how to do it.
Thanks