The previous topics explained how you could publish Exchange using one of Microsoft's reverse proxy solutions. However, a reverse proxy is not a required component to make Exchange available from the Internet.

Typically, a reverse proxy is used to provide additional security by providing features such as, pre-authentication or connection filtering. While both of them can be useful, there is no definite need for them.

When taking a look from a distance, one could argue that the Client Access Server basically performs somewhat the same tasks as a reverse proxy: it authenticates the user and fetches the requested information from the internal servers, in this case being the Exchange Mailbox servers.

I admit the reasoning behind the above statement might seem a bit blunt, but in essence it does represent what's happening. If there is no requirement stating some of the additional security features like pre-authentication...