title: How can the email sender reply address say "do not reply"?
body: <p>Today I registered myself on <a href="http://www.pinterest.com" rel="nofollow">Pinterest.com</a> with my Yahoo account. After registration I got an email for email validation, at the bottom of the email this message was showed by Yahoo:</p>
  
  <blockquote>
    <p>Sender reply address says do not reply</p>
  </blockquote>
  
  <p>and I could also hide this message, I mean it was not in the body of email.</p>
  
  <p>Here is screenshot of my email: <a href="http://imgur.com/ke95B" rel="nofollow">http://imgur.com/ke95B</a></p>
  
  <p>My question is:</p>
  
  <p>How can I use this option when I use 'PHP PEAR' or default mail() function?</p>