This article was previously published under Q234805
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For reasons of scalability, performance, and security, you can install Outlook Web Access (OWA) on a server that is not running Microsoft Exchange Server. The following article describes how to install OWA in this configuration.
Before you install Outlook Web Access, ensure that Microsoft Internet Information Server (IIS) and Active Server Pages are installed on your Windows NT Server. Exchange Server 5.5 can be used with either IIS 4.0 or IIS 3.0; Exchange Server 5.5 SP3 is required for proper Exchange 5.5 Server operation on Windows 2000 Servers, so its OWA components are needed with IIS 5.0.
NOTE: To sucessfully install OWA components from Exchange Server 5.5, install Windows NT 4.0 Service Pack 3 with hotfixes or upgrade your computer to Windows NT 4.0 Server SP4. For additional information, click the article number below to view the article in the Microsoft Knowledge Base:
NOTE: You do not have to install Windows NT 4.0 SP3 to install Active Server Pages from the SP3 CD.
Run the Exchange Server Setup program.
When you select components to install, click to clear all check boxes apart from OWA.
Continue with Setup. You are prompted for the name of the Exchange Server computer that OWA will use to look up directory information for mailboxes.
IMPORTANT: The server that you install OWA on must be able to verify the service account on the Exchange Server computer that you indicated. For this to succeed, the IIS and OWA server must either be in the same Windows NT domain as the Exchange Server computer, or have a trust relationship established with the domain that the Exchange Server computer resides in. Failure to satisfy one of these conditions results in system attendant errors during setup.
In this configuration, the NTLM authentication protocol does not work because NTLM only propagates over one network hop (that is, the hop between the browser and the IIS/OWA server). Use Basic/Clear Text authentication as an alternative; this allows browsers to access all resources regardless of the location of their Exchange Server computer.
After Setup is finished, users can log on to their mailbox by using OWA, and the requests will be forwarded to the Exchange Server computer appropriately.