I am encountering the same issue. My configuration in /etc/defaults/opendkim are ignored, and it’s not clear either if my configuration in /etc/opendkim.conf is being read. Opendkim is not configurable!
For comparison, in Debian 8 the execute string in the /etc/init.d/opendkim file reads: DAEMON_OPTS="-x /etc/opendkim.conf -u $USER -P $PIDFILE $DAEMON_OPTS” …where $DAEMON_OPTS is has been set as: DAEMON_OPTS="-p $SOCKET $DAEMON_OPTS” and here $SOCKET and $DAEMON_OPTS are coming from /etc/defaults/opendkim.
