Could not copy message

If you get “Could not copy message” or “Can’t open PGP subprocess!: No such file or directory (errno = 2)”, it means your mutt and GPG are not configured to work with one another.

The solution is to source from your ~/.muttrc a mutt/gpg configuration usually in your mutt package. On Archlinux add to your ~/.muttrc:

source /etc/Muttrc.gpg.dist