Hi,
> Since I use X11, emacsclient runs in a separate window (not in mutt's
> terminal). So it doesn't make sense that mutt is "Waiting for
> Emacs..." I mean, why can't it wait for emacs in the background and
> allow me to look at other emails at the same time? Is there an option
> for this, perhaps "async-editor" or something?
AFAIK not, but you can start a second mutt to 'browse' your eMail.
Thomas