Anonymous Request received from HostAddress:”%1″, HostName:”%2″. Invalid Autodiscover site configuration. To fix the problem remove Anonymous access.

This Error event indicates that the Microsoft® Exchange Autodiscover service was unable to process anonymous requests from an Autodiscover client, for example, an Outlook® client. An invalid Autodiscover site configuration and an anonymous client request could cause this error. ‘HostName’ in the error message text refers to the Domain Name System (DNS) name of the remote client.

Autodiscover requires authenticated clients to connect by using either of these methods:

• The client may use a Secure Sockets Layer (SSL) connection to perform Active Directory® directory service lookups to find the requested mailbox database.

• The client may provide URLs of Exchange services such as the Availability service.

We do not recommend that you enable anonymous authentication as this will give spammers access to e-mail addresses. A HTTP 403 error is sent to the client.

To resolve this error, do the following:

• Check the Autodiscover virtual directory site configuration settings on the Exchange Client Access server (CAS) and make sure SSL is selected for Basic or Windows Integrated Windows authentication (also known as NTLM or Kerberos authentication).

• Follow these steps to disable Anonymous access in the Autodiscover virtual directory on the Client Access server.

  1. In Internet Information Services (IIS) Manager, locate the Autodiscover virtual directory.

  2. Right-click Autodiscover virtual directory and select Properties.

  3. On the Directory Security tab, under Authentication and access control, click Edit.

  4. In the Authentication Methods screen, clear Enable anonymous access.

For more information about the Autodiscover service, see Managing Autodiscover.

If you are not already doing so, consider running the tools that Microsoft Exchange offers to help administrators analyze and troubleshoot their Exchange environment. These tools can help you make sure that your configuration is in line with Microsoft best practices. They can also help you identify and resolve performance issues, improve mail flow, and better manage disaster recovery scenarios. Go to the Toolbox node of the Exchange Management Console to run these tools now. For more information about these tools, see Toolbox in the Exchange Server 2007 Help.