Comment # 3 on bug 1191885 from Paolo Panto

To avoid that the ddclient.service is overwritten again by an update, I did the
following:

sudo mkdir -p /etc/system/system/ddclient.service.d/
sudo vim /etc/systemd/system/ddclient.service.d/override.conf

with the following content:

[Service]
SupplementaryGroups=maildrop