Email client that understands both HTML and maildir

I'm using Mutt as my main email client, but I'm looking for another one for my work email (because of HTML email). I need one that can handle my existing Maildir email, to be able to switch between Mutt and the new one without having to import/export my old emails. Does anyone know such email client?. Also I don't want to stop using Fetchmail, Procmail and Exim4. It would be nice to find something similar to Mutt, but with better HTML answering abilities.