Internet mail pointed to Exchange 5.5

I’ve lost my E-mail & hosting Provider for my company’s E-mail service, which handled all of our E-mail services. We would go to their server and retrieve all of our mail. The new Hosting Provider does not provide E-mail services and wants to forward all mail sent to my domain name to my Exchange 5.5 Server which runs on NT 4.0. What modifications in Exchange do I need to make – to make this work. I currently have a public address that points to my Exchange 5.5 Server.