Nginx not serving www.example.com but serves example.com - nginx

Question

I am having problem getting www.example.com to work. Website loads on example.com but not on www.example.com. My current config file /etc/nginx/sites-available/example.com is
server {
listen 80;
server_name www.example.com;
return 301 http://example.com$request_uri;
}
server {
listen 80;
server_name example.com;
root /path/to/dir;
index index_en.html index.html;
}
I have tried different approaches with config, none worked. I also removed the example.com block and went with only one for www.example.com, yet www.example.com didn't work, but example.com still did. Of course I restarted nginx after every change.
I have DNS records for both, example.com and www.example.com, both A and pointing to same IP. I have also tried CNAME-ing one to another, waited for few hours and nothing. Still the same. Now I am getting really pissed off, because with other subdomains everything is working perfectly, just not with www.
And yeah, if I search for www.example.com on Firefox on Ubuntu 14.04, I get Server not found.
# /etc/nginx/nginx.conf
user www-data;
worker_processes 4;
pid /run/nginx.pid;
events {
worker_connections 768;
# multi_accept on;
}
http {
##
# Basic Settings
##
sendfile on;
tcp_nopush on;
tcp_nodelay on;
keepalive_timeout 65;
types_hash_max_size 2048;
# server_tokens off;
# server_names_hash_bucket_size 64;
# server_name_in_redirect off;
include /etc/nginx/mime.types;
default_type application/octet-stream;
##
# Logging Settings
##
access_log /var/log/nginx/access.log;
error_log /var/log/nginx/error.log;
##
# Gzip Settings
##
gzip on;
gzip_disable "msie6";
# gzip_vary on;
# gzip_proxied any;
# gzip_comp_level 6;
# gzip_buffers 16 8k;
# gzip_http_version 1.1;
# gzip_types text/plain text/css application/json application/x-javascript text/xml application/xml application/xml+rss text/javascript;
##
# nginx-naxsi config
##
# Uncomment it if you installed nginx-naxsi
##
#include /etc/nginx/naxsi_core.rules;
##
# nginx-passenger config
##
# Uncomment it if you installed nginx-passenger
##
#passenger_root /usr;
#passenger_ruby /usr/bin/ruby;
##
# Virtual Host Configs
##
include /etc/nginx/conf.d/*.conf;
include /etc/nginx/sites-enabled/*;
}
I left mail section out because it is completely commented out.

Answer 1

It probably had to do with some local DNS settings on LAN and local DNS cache, because I was able to access the site from other networks.