If you're using FreeBSD 6.0 or newer, you can control sendmail very easily by adding variables to your /etc/rc.conf file. Looking at the /etc/rc.d/sendmail file, it seems there are four variables used to control sendmail:
* sendmail_enable * sendmail_submit_enable * sendmail_outbound_enable * sendmail_msp_queue_enable
Setting sendmail_enable to NO will disable all four of those options.
This knowledge base article was supplied by Fleeb.