<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>