In descriptions of Outlook Web Access (OWA), you see the terms rich and reach browsers. A rich browser is a browser that supports features such as XML, Extensible Style Language (XSL), Dynamic HTML (DHTML), and WWW Distributed Authoring and Versioning (WebDAV). Web developers can take advantage of these features to enhance the UI and offload some server processing tasks back to the client. Currently, rich browsers include Microsoft Internet Explorer (IE) 5.5 and IE 5.0 running on the Windows platform.

A reach browser is a browser that supports HTML 3.2 and European Computer Manufacturers Association (ECMA) script standards. Reach browsers include IE 4.02 and earlier and Netscape Navigator 4.08 and earlier.

OWA 2000 detects the browser type when the client connects to the OWA server. The OWA server sends XML and DHTML content to rich clients, thus improving server performance and providing a more dynamic UI. The OWA server sends only HTML content to reach clients.