All email from my server is being marked as spam by Gmail and Outlook. I meet all criteria not to be marked as spam:

  • DKIM
  • SPF
  • PTR

These are all correct, and the headers don't show anything strange.

Why is this happening?

  • Hey old friend! Are you getting bounce-backs or do you have any clues? I assume that the people you are sending e-mail to are not getting it. But is there anything GMail may be giving a clue to? For the record, GMail is a [*****] and unnecessarily so. Cheers!!
    – closetnoc
    Sep 2, 2016 at 2:40
  • @closetnoc Hi!! Thanks for your comment! Nope, no bounces. Everything just lands in the Spam folder. I had a call with Microsoft for the Outlook problem and after being connected several times with "a person who connects people" they admitted my setup was perfectly fine and there's an issue in their system. I'm going to be called back by them today, should this fix the problem then I'll answer my own question :)
    – William
    Sep 2, 2016 at 6:28
  • You rock! Cheers!!
    – closetnoc
    Sep 2, 2016 at 15:48
  • Could you add the email headers as received in Gmail or outlook to your post?
    – Ferrybig
    Sep 7, 2016 at 8:27
  • Did you run your email through Spam Assassin?
    – Robert
    Sep 13, 2016 at 15:20

2 Answers 2


It is possible this is due to the outbound messages not being authenticated with SMTP but instead sent out using a local mailer such as sendmail() without authentication. This has been common on web servers but Gmail and others (more will probably follow soon) have recently started to mark unauthenticated emails as suspicious even when the SPF, DKIM, and DMARC (etc.) checks all pass because they think there is no reason why mail could not be authenticated if it is genuine.

Moving forward this just means web applications should now be configured with SMTP hostname, username and password before they can send authenticated mail in order to survive anti-spam checks successfully.

Further reading: http://fedscoop.com/how-to-fight-phishing


I know this is true for Outlook and Yahoo. I haven't had the problem with GMail. Some email systems will reject email from valid systems if you aren't well known enough(!). That is why a lot of people will use MailChimp or Zoho and other email systems to get around the problem. You can find articles around the 'net about the issue.

Now, this is coming from a guy who runs a few email servers and I do a lousy job of it. But "it works" for the client applications that need it. However, just a couple of weeks ago, I was given a reason we need to get serious about it and, as I type, have a number of tabs open in my browser on what I need to clean up our act. So I won't be expert for at least a couple more weeks.

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