[djcb]

(mu4e author here)

Mu4e has a few different options for displaying rich-text messages. In recent emacsen, it defaults to a shr/eww based display; it's not perfect, but it reduces the set of problem cases.

For those, there are the view-in-browser action, and with (as of yet unreleased) emacs-25 you can use a webkit-based display embedded in emacs.

With those, I'm able to view just about any message; even the ones I get from airlines etc., which tend to be html-only.

Anyway - to get back to the top-level subject: congratulations to mutt, which is a great e-mail client, and a big influence on mu/mu4e.