You want to start to use feedburner.
This article lays out some good ways to do that. http://codex.wordpress.org/Using_FeedBurner
Using plugins, custom functions, and editing .htaccess files.
Because you already have this setup, I would recommend the .htaccess method.
Ask Apache full details. http://www.askapache.com/htaccess/redirecting-wordpress-feeds-to-feedburner.html