Domains resolving to non-www version

Hi everybody,

I'm using Doncha's domain mapping plugin and, after installing WPMUDEV's sitemap's plugin I wanted to give a try to your domain mapping plugin.

I've installed it, replace Doncha's one, and everything's working fine...but all the URLs are resolving to non-www version. That is, in Doncha's plugin you had the ability to map 2 URLs to a given domain (that is, http://www.mydomain.com and my domain.com), and then choose your default url (in my case, the ones with www).

But now, if I type http://www.mydomain.com/ the URL is rewritten to http://mydomain.com/

I've deleted the previous mapping and set it to "www.mydomain.com", but it's not working.

Any ideas?

Thanks in advance.