@cnu, i actually use Emacs for mail composing on office email account. But it only works as an editor only, and is invoked by Mutt . That way i have an easy to use Email client, and easy to use text editor.
Gnus is a Newsgroup cum Email reader. It just needs to be configured either ways. I never got time to read Gnus' documentation to configure it. Writing mutt's config file was easier. If you are keen on using Emacs-integrated-Mutt then you may use this muttrc file:
*db.ilug-bom.org.in/lug-authors/anurag/muttrc