sendmail and qpage are recommended. either or both can be used to send notifications.
Find sendmail at www.sendmail.org
Find qpage at www.qpage.org
Note: this does not need to be the real sendmail, as long as it looks and smells like sendmail.
ie. qmail’s sendmail compatible sendmail program will be just fine.
fping is used by the Ping Monitoring module for ping tests. You almost certainly want to run ping tests.