milter-spamd has been installed as ${PREFIX}/libexec/milter-spamd.
See milter-spamd(8) for instructions on how to register the plugin.

To start the plugin automatically on startup, one can use:

/etc/rc.conf.local
milter_spamd=""

/etc/rc.local
if [ X"${milter_spamd}" != X"NO" -a \
     -x ${PREFIX}/libexec/milter-spamd ]; then
        echo -n ' milter-spamd'
        ${PREFIX}/libexec/milter-spamd ${milter_spamd}
fi