m040601 [1] filed a deletion request for run-mailcap-rs-git [2]: Read the comments. Project was an experience and is abandoned in github for more than three years. There are many many more alternatives to "mailcap" tools both in Arch/AUR. The current PKGBUILD maintainer has no recent activity on the AUR.
[1] https://aur.archlinux.org/account/m040601/ [2] https://aur.archlinux.org/pkgbase/run-mailcap-rs-git/
