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My email is being rejected by GMail because:

550-5.7.25  The IP address sending this message does not have a PTR record 
setup, or the corresponding forward entry does not point to the sending IP.

I have Cyberpanel server suite running on an Ubuntu server. It functions as an email server and a DNS server. It uses Postfix to run the email server. Testing my email with https://www.mail-tester.com/ I get the following message.

Your IP address x.x.x.x is associated with the domain mydomain.net.
Nevertheless your message appears to be sent from mail.mydomain.net.

You may want to change the host name of your server to mydomain.net.

Here are the tested values for this check:

    IP: x.x.x.x
    HELO: mail.mydomain.net
    rDNS: mydomain.net

Should I update my PTR record to be mail.mydomain.net instead of mydomain.net? Or update it to just mydomain.net? If so how to update the PTR record in Cyberpanel?

Edit: Linode provides the server. Apparently you can edit the rDNS value in their admin panel under Networking tab. Still should I change mail server to be the rDNS value or change mail server name to mydomain.net instead of mail.mydomain.net? How is this normally handled?

MindSpiker
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1 Answers1

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So I changed the reverse DNS record to mail.mydomain.net and that fixed my immediate issues with sending to Gmail addresses. I changed this in my server provider (Linode.com) panel. Not sure if having reverse DNS only work for my email will cause problems with my web hosting but so far it's good. As far as I know the only use of my rDNS is for sending email verification, so this may work just fine.

MindSpiker
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  • The reason why you need reverse DNS is because Postfix is sending a SMTP banner with the hostname of the server. Gmail is doing DNS lookup on the hostname in the banner and if reverse DNS on the ip address does not matches the hostname then the likelyhood for the mail spam is a bit higher, which one of the reasons why you mail will land in spam folder or not delivered at all. – Lasse Michael Mølgaard Sep 21 '22 at 04:53
  • Another thing to add is that the rDNS records needs to be made for both version 4 and version 6 IP Addresses with corresponding A records (for v4) and AAAA records for v6. – MindSpiker Sep 21 '22 at 16:55