stopping mail

I made a monitor from my machine (CentOS 4.5) to do an http to a machine
retrieve some info to see if a process is running (on this remote machine I have
a task running so it is easy to get the info from my machine).

If I cannot access the remote machine, my machine sends mail to me and a couple
other people saying the machine is unreachable.  My cronjob runs every 5 minutes.
Juts occured to me now though that if our network goes down, my machine will be
sending mail every 5 minutes saying the machine is unreachable.  These messages
will get stored on my machine and all get sent when it comes up.

I am wondering whether someone knows how to cancel mail that is queued on a machine, so it
doesn't all get sent out.  I do have root access.