In our test lab, we installed Microsoft SharePoint Services beta 2 on a Microsoft Exchange Server 2003 front-end server. As soon as the installation was finished, we noticed that Microsoft Outlook Web Access (OWA) on the front-end server no longer worked. Is this a known conflict?
SharePoint Services will try to use its built-in rendering mechanism to render URLs requested on servers on which it's installed. This action is
poison for OWA, which wants to render its own content.
The remedy is straightforward: Use the SharePoint Services exclusions list to tell SharePoint Services not to attempt to render the /exchange, /public, or /exchadmin virtual directories.
—Paul Robichaux