"Anonymous authentication enabled for virtual directory" error when you use the Remote Connectivity Analyzer tool to send an anonymous HTTP request from the remote server to the URL in Office 365

Note The following scenario only applies to Microsoft Office 365 customers who have a hybrid deployment of on-premises Exchange Server and Exchange Online.

You try to use the Microsoft Remote Connectivity Analyzer tool to test Autodiscover redirection in an organization. During the test, the Remote Connectivity Analyzer tool tool sends an anonymous HTTP request from the remote server to the URL that's responding with the Autodiscover address for the on-premises hybrid server. If the request succeeds, but anonymous access should not be enabled on this virtual directory, you receive the following error message in the tool:

This issue occurs because the following applications and services require specific authentication methods:

• Outlook Web App
• Microsoft Exchange ActiveSync
• Outlook Anywhere (formerly known as RPC over HTTP)
• Autodiscover
• Other Exchange Web Services such as the Availability Service and web-distributed Offline Address Books

If anonymous access is enabled instead of, or in addition to, other required authentication methods, your server is not as secure from a security perspective, and unexpected results can occur.

To resolve this issue, review the following documentation and confirm that the correct authentication methods for each application or service are enabled for the virtual directories on your Exchange server:

• For more information about a list of the default virtual directory settings for Microsoft Exchange Server 2010, go to the following Microsoft TechNet website:
  
  Default settings for Exchange-related virtual directories in Exchange Server 2010
• For more information about a list of the default authentication methods for Microsoft Exchange Server 2007 applications and services, go to the following Microsoft TechNet website:
  
  Default settings for Exchange-related virtual directories in Exchange Server 2007
• For more information about how to configure authentication that is specific to Outlook Anywhere in Exchange Server 2010 and 2007, go to the following Microsoft TechNet website:
  
  Configure Authentication for Outlook Anywhere

Still need help? Go to the Office 365 Community website.