IIS doesn't serve unknown MIME types

Ever experienced working on a web project that works perfectly on dev and stage servers then shows up 404 in production? I experienced this as was troubled for some time. Usually, production servers have limited access and configuring it might is probably out of option. 

good thing, it can be configured on your config file.

(lets assume a non-standard extension and treat it like an XML)

for IIS 7 and above versions.

    

        
            
     

    







As for IIS 6, I think it is not possible to configure in config. You will really 

have to kneel down server admins, so deal with them even if they are stubborn.