title: Add unix user to postfix maillogs
body: <p>I am using CentOS 6, and postfix mail server, from postfix mail log, I want to see which Linux user has sent specific email, is it possible? How can this be done?</p>
  
  <p>I need this to prevent spam from our mailservers, by one of our users. I need to figure out which user, and what script.</p>