title: how to avoid my sent email not be classified as spam?
body: <p>I am operating a website that can send invitation to other people, I encountered a problem that the emails sent from my website are all classified as spam in the major email sevice providers, I am just wondering how I can avoid this as much as possible.</p>
  
  <p>Basically what I am doing now:</p>
  
  <p>1) User input friend's email</p>
  
  <p>2) I use python to send the email, the email is simple - pure text, just a line of words to tell people that your friend is inviting you, and the website has created an account for him, the password is **</p>
  
  <p>3) The 'from' of the email is the user who is sending the invitation(I am wondering if this contribute to the spamness?), not my website's email.</p>
  
  <p>Thanks.
  Bin</p>