title: Permission denied when doing Postfix ubuntu tutorial
body: <p>Im working on this tutorial Postfix mail server. 
  <a href="https://help.ubuntu.com/community/Postfix">https://help.ubuntu.com/community/Postfix</a></p>
  
  <p>When i run the command. 
  su - fmaster
  mail</p>
  
  <p>I get the error. 
  Cannot open mailbox /var/mail/fmaster: Permission denied
  No mail for fmaster</p>
  
  <p>also i sign in as fmaster. 
  terminal -> mail. </p>
  
  <p>/var/mail/fmaster: Permission denied
  No mail for fmaster</p>