My email server serves only a few people who are all known to me. I recently forwarded an email from my server to my own GMail account but got this error on my servers mailq.
relay=alt1.gmail-smtp-in.l.google.com[142.250.153.27]:25, delay=90571, delays=90570/0.03/0.62/0.72, dsn=4.7.28, status=deferred (host alt1.gmail-smtp-in.l.google.com[142.250.153.27] said: 421-4.7.28 [85.234.130.200 15] Our system has detected an unusual rate of 421-4.7.28 unsolicited mail originating from your IP address. To protect our 421-4.7.28 users from spam, mail sent from your IP address has been temporarily 421-4.7.28 rate limited. Please visit 421-4.7.28 https://support.google.com/mail/?p=UnsolicitedRateLimitError to 421 4.7.28 review our Bulk Email Senders Guidelines. f15-20020aa7d84f000000b0053318ba2b73si678945eds.692 - gsmtp (in reply to end of DATA command))
The claim that my server has sent unsolicited email is nonsense. I have checked the mail logs and only myself and one other user has sent any email and they are not unsolicited.
So the claim is definitely spurious. I already had SPF configured. I have now set up the reverse DNS to match the forward DNS look up in case that had any effect. After sending a further test email it is still rejected.
I have even now gone to the trouble of adding DKIM to my server - but Google is still rejecting. As it seems impossible to get to a human being at Google how can I resolve this?
