title: opendkim-testkey: [path]/dkim.key: open(): permission denied
body: <p>I installed postfix on an Ubuntu 16.04 LTS server and tested the default settings.  I was able to send a test email successfully.  Then I wanted to add dkim, which is where I started running into a problem.  My emails don't seem to be getting signed.</p>
  
  <p>When I run</p>
  
  <pre><code>opendkim-testkey -d mydomain.com -s mail -vvv
  </code></pre>
  
  <p>I get</p>
  
  <pre><code>opendkim-testkey: /etc/postfix/dkim.key: open(): Permission denied
  </code></pre>
  
  <p>Ownership and permissions for /etc/postfix/dkim.key</p>
  
  <pre><code>-rw------- 1 opendkim opendkim   887 Sep  7 16:07 dkim.key
  </code></pre>
  
  <p>Postfix is also a part of the opendkim group</p>
  
  <pre><code>postfix : postfix opendkim
  </code></pre>
  
  <p>I hope someone has an idea, because I'm here scratching my head on this one.</p>