To enable smtpfwdd via rc.d script please add smtpd_enable="YES" 
in your rc.conf.

You must follow the next steps, as root, in order to finish the installation:

1) Make sure uucp is a trusted user to sendmail.
   To do this, check if your sendmail.cf has a line with "Tuucp"

2) Disable sendmail from answering smtp requests, but make sure it
   handles queue delivering.  You have two choices:

   a) Start sendmail without the "-bd" flag, but with the "-q30m" one.
   b) Do not start sendmail as a daemon, and add an entry in /etc/crontab
      to run sendmail -q when needed.  For example, add the following line
      to your /etc/crontab:
*/30	*	*	*	*	root	/usr/sbin/sendmail -q

   In any case, you'll most likely have to edit /etc/rc.conf to change
   sendmail configuration.

3) Add smtpd to your inetd.conf:
	smtp stream tcp nowait root %%PREFIX%%/sbin/smtpd smtpd

4) smtpd runs in a chrooted environment, so you must feed this environment
   with any configuration file it needs.  Make a copy of /etc/resolv.conf
   and /etc/localtime to %%SPOOLBASE%%/etc.  If you ever change any of these
   files, remember to change the copies also.  Do not make a symbolic
   link, as it will not work in the chrooted environment.

5) Create your own %%SPOOLBASE%%/etc/smtpd_check_rules.  There are some
   examples in that directory.  If have any problem, take a look at
   http://www.obtuse.com/juniper-docs/man/smtpd_address_check.html.

6) Reboot !   (Or restart all those daemons manually, if you know how :^) )