Opendkim: key data is not secure

Hi Josh,

I found this warning in /var/log/mail.log. Nothing bad, but it’s always better to be informed about it.

Jul 23 10:33:48 kroepoek opendkim[4036]: mydomainname.com: key data is not secure: opendkim is in group 33 which has multiple users (e.g., “www-data”)

See https://github.com/mail-in-a-box/mailinabox/issues/379.