I used sup for many years (and contributed some very minor patches). sup is no longer maintained and it's difficult to get running with ruby 1.9. Some good people that weren't happy with sup created notmuch (http://notmuchmail.org/) with similar goals. There is a mutt fork that uses morning called mutt-kz (https://github.com/karelzak/mutt-kz/wiki).

I'm not as satisfied with mutt-kz as I was with sup, but it's probably even better if you have invested a lot of time configuring mutt just so.