IIS, by default, blocks access to any file types it doesn’t recognise. If a dot (.) is in the URL, IIS assumes its a file name and blocks access. To allow dots in a URL on an IIS site (perhaps for domain names/email addresses/etc. in a MVC routing path) you have to make a couple … More Allow Dots in URL (IIS)
If using IIS Express (the default for debugging web applications in Visual Studio), you can use domains other than localhost but its not particularly intuitive.