Address not found, 550 5.1.0 Recipient rejected, Google Cloud

clyde01

• December 09, 2019 04:42

Hi, I have set up a VM instance on Google Cloud Platform (GCP) running CentOS 7.7 with WHM v84.0.16 installed. I have configured Exim with mailgun and it is able to send emails out via mailgun. However, I am unable to send email from my Gmail to my DOMAIN email (I am able to receive emails sent out from my DOMAIN email). I encountered the 550 5.1.0 Recipient rejected error message whenever I try to send an email to my DOMAIN email. I have :

• acquired my domain name from Namecheap and have configured the nameservers in Cloud DNS (currently using google nameservers)
• enabled the Public DNS PTR record to my VM instance
• configured SMTP to use port 2525 instead of port 25 as GCP blocks it
• ports 465, 587 and 2525 have been allowed on the firewall and I am able to telnet in at port 2525
• Email Deliverability reports configurations as valid in both WHM and cPanel
• added MX records to point to mail.mydomain.com

• 

  cPanelLauren

  • December 10, 2019 19:39

  Hello @clyde01

  • When you send mail to yourself from Gmail, is the transaction (or even SMTP connection) logged in the exim log at /var/log/exim_mainlog
    
  • Is the domain located in /etc/localdomains
    and not present in /etc/remotedomains
    ?
  • Is there a CNAME record present for mail.mydomain.com (i.e., does it resolve to an IP address)
  • Does this only occur with Gmail or does it also occur with other email service providers
  • Do you now or have you ever had Google's email suite?

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• 

  clyde01

  • December 11, 2019 11:00

  Hello @cPanelLauren,

  • No, there is it a transaction logged in the exim log when I send an email to the DOMAIN email
  • Yes, the domain is located in /etc/localdomains and NOT present in /etc/remotedomains
  • No, there is no CNAME record present for mail.mydomain.com, instead I have an A record resolving mail.mydomain.com to the IP address
  • No, it also occur with other email service providers
  • No, I never had Google's email suite (GSuite)

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• 

  clyde01

  • December 11, 2019 13:00

  Hello @cPanelLauren, Support has helped me resolved the issue, it turns out I have blocked port 25 inbound to my VM instance. Google blocks OUTBOUND port 25 traffic, so the blunder is on me.

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