Bypass Gmail's spam filter (mails sent with PHP from a shared host)

Question

TL;DR: Mails sent from shared hosting (such as a cheap domain from Unoeuro or One.com) end up in spam. How to fix?

---

I made a mail-system, that

Answer 1

One thing to bear in mind, I had trouble with emails being blocked by Gmail and Yahoo! mail from php because the Return-Path header didn't match the from. On a lot of servers if you explicitly set the Return-Path in the headers PHP Mail will ignore that and set the return path to the machine name. You have to force it in the 'additional parameters' section of the mail function using the '-f' flag. Now I've never used Swift Mailer so I don't know the equivalent to PHP's native mail() function, but here's what it would look like using mail();

mail($to,$subject,$message,$headers,'-f returnpath@example.com')

If you can find out the equivalent to this in swift mailer it might solve your problem.

Edit:

It looks like you're not actually setting the Return-Path at all. I know GMail really doesn't like that to be left out. Try setting it explicitly to your Swift_Mailer message (and make sure it matches your From):

$message->setReturnPath('from@example.com');