.muttrc, .mime.types, .mailcap, .urlview.
Here's a tar file (2 MB),
which contains mutt-1.1.9i, compiled for SGI IRIX 6.5,
plus config files: muttrc, mailcap, mime.types, and .ulrview.
It also contains a few helper scripts,
(fromerly known as MSWordView), a Word-to-HTML/Text converter,
all compiled for SGI IRIX.
(The link for MSWordView used to be http://www.csn.ul.ie/~caolan/, but it's gone dead).