This issue is actually pretty common, but really shouldn't be an issue. It's a matter of DNS. When your website is setup on a server, that's server will create new DNS records for your site. There are multiple DNS records. One is for mail, one for your domain name, another for your domain name with "www." in front, etc. I'm surprised to find even high class sites, or high traffic websites that don't have their DNS configured properly. If this is an issue on your website, contact your server administrators. If it's your server, add another DNS record accordingly.