GMail blocking messages passed from postfix

Heya people,

So I recently finished setting up postfix for my website. It forwarded fine to most hosts I tested for, but to my surprise gmail rejects every e-mail with

Our system has detected that
    550-5.7.1 this message is likely unsolicited mail. To reduce the amount of
    spam 550-5.7.1 sent to Gmail, this message has been blocked. Please visit
    550-5.7.1  https://support.google.com/mail/?p=UnsolicitedMessageError 550
    5.7.1  for more information. q2si17378356pgp.400 - gsmtp (in reply to end
    of DATA command)

So I'm currently trying to do what is recommended in that support link, but so far this hasn't changed anything. Can I do anything to get gmail to not refuse my emails? Eventually I will need things to be distributed to multiple addresses (various people) and I'd rather not have to have them configure their gmail accounts specifically for the purpose of receiving these mails.

So yeah, does anyone know what I need to change for gmail not to complain? Running Ubuntu 16.04.

Cheers,

Ronan

2 Replies

Not easy to help you without specific details…

Try and see the most typical things, like: setup your Reverse DNS, setup correct DKIM, SPF and DMARC, setup TLS certificates with Let's Encrypt so your postfix responds with a valid certificate. Take a look at this postfix configuration to take ideas.

Then test all that via the various typical services, like:

https://www.dnsbl.info/ (blacklist check)

https://www.ssllabs.com/ssltest/ (SSL/TLS certificate check)

https://intodns.com/ (DNS and Reverse DNS check)

https://dmarcian.com/dmarc-inspector/ (DMARC check)

https://mxtoolbox.com/SuperTool.aspx (multiple check tools into one)

https://www.unlocktheinbox.com/ (more multiple check tools)

Finally, make sure you do NOT send any spam, because none of the above will help you ;)

Heya,

thanks for all the info, got dkim, dmarc and spf working after a bit of work and things seem to send fine now. Messages go to spam in gmail but that's a one time fix so I'm fine with it.

Thanks again!

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