how to avoid my sent email not be classified as spam? [closed]

Question

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.

Basically what I am doing now:

1) User input friend's email

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 **

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.

Thanks. Bin

Answer 1

1. How to send emails and avoid them being classified as spam will give you some useful tips.
2. Ways to prevent email being blocked as Spam