title: how to avoid to being identified as spam when using smtplib in python
body: <pre><code>import smtplib
  
  smtp = smtplib.SMTP()
  smtp.connect('smtp.163.com', '25')
  
  
  from_addr = 'XXX@163.com'
  to_addr = 'XXX@qq.com'
  
  
  smtp.login(from_addr, 'XXXX')
  
  
  
  msg = ('From: %s\r\nTo: %s\r\n'
  % (from_addr, to_addr))
  
  msg = msg + '''Subject: Test
  
  Hi, I just test this format!!
  Just python send mail test - -.'''
  
  smtp.sendmail(from_addr, to_addr, msg)
  smtp.quit()
  </code></pre>
  
  <p>I dont know why the message has been always classified as spam, I will appreciate for any advice for me.</p>