Hi yes you do need to turn sendmail on it is off by default to do this open /etc/hostconfig in emacs or whatever as root and change
MAILSERVER=-NO-
to
MAILSERVER=-YES-
then reboot and sendmail will be running and you can use it instead of your isps smtp server, although I think the configuration needs some tweaking because I've had problems with sending some attachments, I just can't be bothered to sort it out just yet...
Have fun
Marc