title: Crontab send email to root and postmaster
body: <p>I'm on a fresh server and I added (few days ago) a line in my <code>crontab -e</code>.</p>
  
  <p>Since that, each time the cron is running, my server try to send an email to root (my gmail) and to an email like <code>postmaster@my_server.my_ip</code>.</p>
  
  <p>My problem is emails sent to root (my gmail) are ok, but emails sent to <code>postmaster@my_server.my_ip</code> are all delayed, and I receive <strong>A LOT</strong> of emails from Mail Delivery Subsystem  like :</p>
  
  <ul>
  <li>Delivery to the following recipient has been delayed ....</li>
  </ul>
  
  <p>It looks like gmail cannot sent email to <code>postmaster@...</code></p>
  
  <p>My questions :</p>
  
  <ul>
  <li>Why cron send emails to root and postmaster each time ? I did not do anything for that.</li>
  <li>How can I disable that ?</li>
  </ul>
  
  <p>Thanks !</p>