Webhosting Terms and Definitions
Sub-domains are domain names with the form, anything.yourdomain.com. By definition, a subdomain should not be a domain name having the prefix of "www".
In order to access this domain with the "www" prefix (i.e. www.anything.yourdomain.com), you would have to create a "sub-third-level domain" with the prefix "www.anything".
Here is a chart of Free Webhosting with SMTP and Free Email Service.
Free Web Hosting