<IfModule mod_headers.c>
    <Directory "/usr/local/cpanel/3rdparty/mailman/archives">
        # If a Content-Type has not already been set by other means, apply the default of application/octet-stream so the file will be treated as a download.
        Header add Content-Type application/octet-stream "expr=-z %{resp:Content-Type}"

        # Prevent the browser from attempting to guess the Content-Type.
        Header set X-Content-Type-Options "nosniff"
    </Directory>
</IfModule>