Stop Cron Daemon Emails

I’m getting thousands of (Cron Daemon) email messages in my gmail ever since I got Postfix working. Obviously, I need to stop these messages. I’ve tried the usual, looking into crontab -e, looking into crontab -e as root, /etc/crontab. And I can find nothing.

Taking more drastic measures, I stopped cron and postfix like this:
sudo service postifx stop
sudo service cron stop

That didn’t work. So for fun I did this:
sudo systemclt stop postfix
sudo systemctl stop cron

Still no luck!

I can check the status of Postfix and cron, and verify that the service is inactive.
sudo service postfix status
sudo service cron status

In both cases they are both inactive (dead)

Next step I take is block outbound port 465, 25, 587, 2525 using ufw
sudo ufw deny out 465
sudo ufw deny out 25
sudo ufw deny out 587
sudo ufw deny out 2525

So far I have made postfix and cron inactive and blocked a bunch of outbound mail ports and I’m still getting (Cron Daemon) messages in my inbox (gmail)

Any idea how I can find and stop these? I’m running Ubuntu 18.04 and getting emails every 60 seconds. There is no cronjob that I can find anywhere that is setup like this:

          • /path/filename

What am I missing?

The easiest way is probably to put this at the top of the crontab:

MAILTO=""

Alternatively you can silence cron jobs selectively by adding this to the end of that line entry:

>/dev/null 2>&1

So your full crontab entry would look something like:

0 2 * * * /home/backup.sh >/dev/null 2>&1