nginx server_name directive not working

I want to use nginx as a proxy server for my application. A part of the conifguration looks like:

server { listen 80; server_name my.example.net my.example.net; location / { proxy_pass actual-url-to-my-app-home-page; } }

The configuration file when used allows me to test my app by using localhost in the address bar. However, http://my.example.net does not work. Any idea what could be wrong? Or am I not correctly understanding or using nginx?

Thanks