IIS not allowing me to server files with .rdp extension

I am trying to host a .rdp file that will be publically available on the internet (without password, of course). IIS is not letting me use this file - I'm getting a 404 error saying it cannot find the file. It works fine if I change the file extension to .txt.

Any idea what I'm doing wrong?

I recommend you try adding a .RDP MIME type to your website configuration in IIS

File name Extension: .rdp

MIME type: application/rdp

+1 with ChrisNZ's tip, and:

In case you run IIS 7.5:

• Start the Internet Information Services (IIS)-Manager
• Unfold [+]Servername and [+]Site and [+]Default Web Site and find the site you'd like to serve that file from and select that site
• At the right pane, find the 'Request Filtering' icon in the IIS section and double-click it
• Now you should see a list of file extensions and their allowance; by default all of them are set to 'false'
• Right-click and select: 'Allow File Name Extension' -> Put .rdp in there.