Net Tools is detected by many antivirus and internet security software as a hack tool. It is not a virus by any means. Before you start saying a file has a virus, make sure you actually read what your antivirus software actually says and what it is actually detecting.
On top of that, there's many websites, applications, and even your command prompt that allows for you to send fake emails. But to make it fair, I've never heard of the website posted above, but I have heard of deadfake. Just look on google for anonymous mailers.