title: Redmine on RHEL 6 not sending emails - AUTH mechanism LOGIN not available
body: <p>I have RHEL6 with installed Redmine 2.6. While trying to set up sending emails I got the error : </p>
  
  <pre><code>504 5.3.3 AUTH mechanism LOGIN not available
  </code></pre>
  
  <p>More than all, while changing the password of an account, the email came to me successfully. Hmm...</p>
  
  <p>So i tried googling that trouble but that gave me no resolved issues. Please, help me to understand how to find out what is wrong. That is important !</p>