title: Gmail SMTP error - Temporary block?
body: <p>I am using Gmail servers to send email from my system, with a program.
  Recently I started getting errors like this:  </p>
  
  <blockquote>
    <p>Data command failed: 421 4.7.0 Temporary System Problem.  Try again later (WS). 6sm3756432pab.11 - gsmtp</p>
  </blockquote>
  
  <p>The reasons are given in <a href="https://support.google.com/a/answer/3726730?hl=en" rel="noreferrer">the support</a>.</p>
  
  <p>Can anybody tell me what is the number of emails that can trigger this issue? </p>
  
  <p>Or is it because of some other reasons?</p>