When you specify authentication for Outlook Anywhere, you provide the authentication method which will be used by the Outlook 2007 client. This authentication method is automatically provided to the client by the Autodiscover service. Additionally, this is separate from the authentication method on the /rpc virtual directory located on your Microsoft Exchange Server 2003 Client Access servers. By default, in the original release (RTM) version of Exchange 2007, the /rpc virtual directory is enabled for both Basic authentication and Integrated Windows authentication and cannot be modified. In Exchange 2007 Service Pack 1 (SP1), the authentication method on the /rpc virtual directory can be modified by using the Set-OutlookAnywhere cmdlet to be either Integrated Windows authentication or Basic authentication. For more information, see How to Configure Authentication for Outlook Anywhere.

You can use Basic authentication with Outlook Anywhere. Basic authentication requires a user name and password, and then sends the user name and password over the Internet in plain text. As long as you use Secure Sockets Layer (SSL) to help secure the connection between the Microsoft Office Outlook Web Access client and the Microsoft Exchange messaging infrastructure, using Basic authentication with Outlook Anywhere is supported. For more information, see How to Configure Authentication for Outlook Anywhere.

NTLM is a method of authentication based on Integrated Windows authentication. We recommend using NTLM Authentication. However, if you are using a firewall that does not handle NTLM, you must use Basic authentication over SSL. For more information, see How to Configure Authentication for Outlook Anywhere.

For more information about Outlook Anywhere, see the following topics:

• Overview of Outlook Anywhere
  
  
• Recommendations for Outlook Anywhere
  
  
• Managing Outlook Anywhere