Dublicate sitemaps

If I have a blog with a mapped domain, the plugin allows me to use two different urls to access the sitemap.

1. The first is the original url http://myoriginalurl/blogname/sitemap.xml
2. The second is the mapped url http://themappedurl/sitemap.xml

The original url should be redirecting to the mapped url, because Googlebot can't follow the links if the link's target is different than the url, which is mentioned in the sitemap.

Example:

1. If I access the sitemap with the original url, permalinks looks like http://myoriginalurl/blogname/postname
2. If I click the permalink, I'll be redirected to the mapped url: http://themappedurl/postname
2. The problem is that Google doesn't allow this behavior and fails to follow the links