This Warning event indicates that the provider specified in the client request and response schema could not be found by the Microsoft Exchange Autodiscover service. When the client specifies an incorrect provider in the request and response schema, Autodiscover will be unable to process the request successfully. In the client request and response schema, the targetnamespace attribute indicates the provider that Autodiscover must route the client request to.

To resolve this warning, do one or more of the following on the Exchange Client Access server:

• Check the Internet Information Services (IIS) logs to identify the client making the request.
  
  
• Contact the client application provider to obtain a valid provider for the client request.
  
  
• Resolve your issue by using self-support options, assisted support options, and other resources. You can access these resources from the Exchange Server Solutions Center. From this page, click Self-Support Options in the navigation pane to use self-help options. Self-help options include searching the Microsoft Knowledge Base, posting a question at the Exchange Server forums, and others. Alternatively, in the navigation pane, you can click Assisted Support Options to contact a Microsoft support professional. Because your organization may have a specific procedure for directly contacting Microsoft Technical Support, be sure to review your organization's guidelines first.
  
  

If you are not already doing so, consider running the Exchange tools created to help you analyze and troubleshoot your Exchange environment. These tools can help make sure that your configuration aligns with Microsoft best practices. They can also help you identify and resolve performance issues, improve mail flow, and better manage disaster recovery scenarios. To run these tools, go to the Toolbox node of the Exchange Management Console. To learn more about these tools, see Managing Tools in the Toolbox.