Can I install Outlook Web Access (OWA) 2000 on a different machine than my Exchange server?
—Johan Verbeke
No, you can't. In Exchange Server 5.5, OWA is a set of Active Server Pages (ASP) that can run on any Microsoft IIS machine. The ASP retrieves mail from the user's Exchange mailbox and presents it. However, the requirement to use ASP limits the number of concurrent users you can squeeze out of one OWA server, so Microsoft rebuilt OWA 2000 so that it no longer uses ASP. Instead, IIS accepts requests for mail data and passes them to Exchange over the Exchange Interprocess Communication (ExIPC) engine. The Store fetches the mail data, uses whatever Web Storage System (WSS) form is required to render it, then returns the data to the client. This approach yields great scalability, but it means that Exchange and IIS must run on the same machine. You can still install IIS on a separate machine, but you can't get OWA to run on that machine. In addition, you can't use the Exchange 5.5 version of OWA to access Exchange 2000 Server mailboxes, though you can use OWA 2000 to get to public folder replicas that are on Exchange 5.5 servers. Most often, people ask how to do this when they want to put an OWA server outside their firewall or in a demilitarized zone (DMZ). The best way to accomplish that goal with Exchange 2000 is to use a front-end server, because it doesn't contain any mailboxes.