So you want to know when your monitoring system fails, or your cron jobs don’t run? Add this to your crontab:
MAILTO=me@me.com
Now install a mail-sending agent. I like ‘nullmailer‘, which is much smaller than most mail-sending agents. It can’t receive or forward mail, only send it, which is what I like about it. No chance of a spammer using my server for something nasty.
The way I have it set up, I’ll have a server (avalanche) sending all email from one address (nullmailer@avalanche.za3k.com) to one email (admin@za3k.com), and that’s it. Here’s my setup on debian:
sudo apt-get install nullmailer
echo "admin@za3k.com" | sudo tee /etc/nullmailer/adminaddr # all mail is sent to here, except for certain patterns
echo "nullmailer@`hostname`.za3k.com" | sudo tee /etc/nullmailer/allmailfrom # all mail is sent from here
echo "`hostname`.za3k.com" | sudo tee /etc/nullmailer/defaultdomain # superceded by 'allmailfrom' and not used
echo "`hostname`.za3k.com" | sudo tee /etc/nullmailer/helohost # required to connect to my server. otherwise default to 'me'
echo "smtp.za3k.com smtp --port=587 --starttls" | sudo tee /etc/nullmailer/remotes && sudo chmod 600 /etc/nullmailer/remotes
Now just run echo "Subject: sendmail test" | /usr/lib/sendmail -v admin@za3k.com to test and you’re done!