http request - How to implement fallback layer, if one authenfication way fails

I have created a program in C#.NET that also fires http queries and runs entirely on the intranet. These queries use NTLM authentication, which in rare cases may not work. For this case I would like to implement some kind of fallback layer that uses Basic Authentication with a stored default user. This default user has very limited rights, but this is usually sufficient. Nevertheless, my code should then send a mail to an internal distribution list, so that we get the problem.

What is the best way to implement such a fallback layer?

As a standalone class with the Chain of Responsibility pattern?

Basic structure:

• Client wants to fire a http query
• Handler checks if the NTLM authentication works
• If the NTLM authentication does not work (401), it uses the basic authentication with the stored default user
• Info mail goes to internal distribution list
• If Basic authentication does not work either (401), an error is issued and info mail goes to internal distribution list