How do I setup e-mail notiifcations

I am a new ubuntu user as well as new nagios user. I installed ubuntu solely so I could use nagios. I was able to install nagios and get it to monitor a few devies (Routers, Switches, Servers), without very few hiccups. Now I want to setup e-mail notifications so that I can know when a service goes down. Does anyone have a HOW-TO I can follow?

I am able to send e-mail using postfix if I telnet:
[blockquote]telnet mail.yourdomain.com 25
ehlo yourdomain.com
mail from: [email protected]
rcpt to: [email protected]
data
Subject: My first mail for my domain
Hi,
Are you there?
regards,
Admin
.
quit [/blockquote]
I’m not sure if that helpe me or not with nagios.

Any help is very much appreciated.