You need to make sure sendmail starts up as sendmail -bd from
your rc.d scripts. There's not real need to have it run the queue every 15
minutes (many distribtions startup sendmail as sendmail -bd -q15
which isn't necessary). When you connect to demon you should find sendmail
automatically delivering mail, sent from Demon, to local users.
To send mail out just issue the command sendmail -q when you
connect to Demon. The ip-up script is a good place
to put this.