Hi! You can use the following service file for gross. It is proved to work.
***gross.service [Unit] Description=Gross greylisting server Documentation=man:grossd(8) After=network.target [Service] Type=forking User=gross Group=gross RuntimeDirectory=gross PIDFile=/run/gross/gross.pid EnvironmentFile=/etc/default/gross ExecStart=/usr/sbin/grossd -P /run/gross/gross.pid ${DAEMON_OPTS} [Install] WantedBy=multi-user.target -- Regards, Dmitry Mikhirev