IIS: How to serve a file without extension?

I am using IIS 8 on Windows 8.1. I have an XML file an I need to have it accessed through (servername)/(path)

(path) is predefined by someone else and does not contain an extension. I tried the simple solution of removing the .xml file the file name, but IIS returns HTTP Error 404.3 - Not Found

In the "Physical Path" returned with the error is the correct file path, which when I copy-paste to Run opens the correct file.

Please let me know if this is possible.

Assuming (path) is a physical directory on your machine, create a new web.config file in that directory with the following content:

<?xml version="1.0" encoding="UTF-8"?>
 <configuration>
     <system.webServer>
         <staticContent>
             <mimeMap fileExtension="." mimeType="text/xml" />
         </staticContent>
     </system.webServer>
 </configuration>

You are telling IIS that for this directory only, any file without an otherwise defined extension (in MIME types) should be considered an xml file. Other file types in the same path should still work.

If you have the Windows feature IIS Management Scripts and Tools installed, you can use PowerShell to create such a web.config file:

Add-WebConfigurationProperty -pspath 'MACHINE/WEBROOT/APPHOST/Default Web Site/.well-known'  -filter "system.webServer/staticContent" -name "." -value @{fileExtension='.';mimeType='text/xml'}

in this example Default Web Site is the name of the web site and .well-known is a directory under that site.

It can be done in IIS 6 as well / without using web.config, but instead using the management GUI to add a MIME type for extension . here:

For instance, to serve a .well-known/acme-challenge token, create a virtual directory called .well-known, and have it take its contents from a physical directory (that cannot have names with leading dots in windows). Then add a text/plain MIME type for the extension . in this directory, and you can manually acquire new letsencrypt certificates for a domain that is currently served by an old IIS.

Changing the configurations by hand can be error-prone. So Internet Information Server (IIS) console GUI provides an easier and error-free way to update the MIME-types. The screenshots shown in the steps below have been taken from Windows 10 box having IIS v10:

1. Open IIS

2. Expand your website's node in the left navigation pane.

3. Select your application or virtual directory.

4. Double-click MIME Types feature under IIS section in the right pane:

   

5. Click Add.. link in Actions pane.

6. Set up the mime type to support all files without extension and click OK :

   

Behind the scene, these steps make changes to web.config file of your application or virtual directory (under your website) as suggested by @PeterHahndorf in his post.