Question

How to configure Reverse DNS for multiple virtual servers in virtualmin

Posted April 8, 2016 6.1k views
Email DNS

I have read most of what i can find but cant find an answer.

Essentially I have a droplet with a domain that I dont use.

In that droplet I have Virtualmin and have three servers, each with emails.

They are having their mail blocked because there is no reverse DNS set up for the domains.

I have read that Digital Ocean sets up the reverse DNS automatically for the domain associated with it. However, there appears no way to set the reverse DNS for the sub servers.

How can i do that?

Just to make it clearer, I have a domain masterdomain.com that I set my droplet up on.

I have customer1.com on a virtual server setup in VirtualMin and his emails are being blocked because the domain lacks a reverse DNS PTR record or whatever you call it.

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jceng
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jceng
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2 comments
  • jceng April 8, 2016
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    Well, I spend 10 minutes expanding on this only to have my answer blocked by Digital Ocean as spam

  • kamaln7 April 8, 2016
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    @jceng Hi! I’m sorry about that. Unfortunately the spam filter catches some actual non-spam posts every once in a while. I’ve just published your post with the details and it should now be visible to everyone.

These answers are provided by our Community. If you find them useful, show some love by clicking the heart. If you run into issues leave a comment, or add your own answer to help others.

2 answers
gparent April 8, 2016

PTR records are associated with the name of your droplet. By renaming your droplet, you set the PTR record associated with its IP address.

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  • jceng April 8, 2016

    OK

    I hoped i’d avoid that type of answer.

    NO.

    I have multiple virtual servers, hence detailing the masterdomain.com which the droplet is configured.

    Within that I have three virtual servers on virtualmin.

    When a reverse DNS lookup is carried out on my IP, 1.2.3.4 that Digital Ocean has provided me with it will look to masterdomain.com, not customer1.com.

    A single IP cannot point to multiple domains, ie customer1.com, customer2.com, customer3.com as far as I can see.

    Im looking for an answer to this question PLEASE.

    Reply Report
  • jceng April 8, 2016

    This is not what im looking for.

    I have a domain for my droplet.

    I have multiple client accounts

    the reverse DNS does not point to their domains, but instead to the Digital Ocean domain that the droplet is set up on.

    Its detailed in the question.

    I included the rejection but my awnser got blocked by digital Ocean as spam.

    Reply Report
    • gparent April 8, 2016

      Indeed, PTR records are not what you should be looking at. Instead, you need to make it so that your mail server announces the correct fully qualified domain name (FQDN), which matches your PTR, regardless of the customer domain it’s sending mail for.

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    • gparent April 8, 2016

      It looks like the error is saying you don’t have a PTR record, not that it’s incorrect.

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      • jceng April 8, 2016

        To be honest, im beyond caring really. I have modified my droplet to mail.masterdomain.com and will see how that works out. The reason im frustrated is that stupid spam comapnies create black lists and its always me that gets it in the face ‘oohh, my emails are being blocked, boo hoo’. And then theres customers that just dont understand the complexties of DNS and servers, 'I sent you the email 5 minutes ago, why isnt it fixed’. Of course, i dont understand enough as i really dont care that much, its always something, its not even worth trying really, something else will go wrong. Im getting customers now saying their broadband IP is blocked, and thats not even me. And to be honest, this forum has never been any use. I think the owners should prune out all incomplete answers. Im tired of reading threads that get halfway there and then stop.... Seriously, im not great, but if Digital Ocean are supposed to auto generate a rDNS then why wasnt it there? How are you supposed to trouble shoot that? Set up your own spam black list and try? I blame the police state.

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        • gparent April 9, 2016

          If you’re still struggling with PTR records and how email works, I would suggest something like Google Apps / Outlook 365. Defer the parts that you don’t know to experts, and focus on what you want to do and what you do better.

          “If Digital Ocean are supposed to auto generate a rDNS then why wasnt it there?”

          To be fair, it probably was there. That feature has been working fine for years. If it wasn’t created, it was probably incorrect. You can use the command dig -x 192.0.2.100 in the future, replacing the IP with yours, and that will get you the reverse name associated with that IP address. I couldn’t verify your IP because all the useful troubleshooting information has been removed.

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jceng April 8, 2016

Just to help out im including the error message

Reporting-MTA: dns; masterdomain.com
X-Postfix-Queue-ID: 7D58E12032C
X-Postfix-Sender: rfc822; customer@customer1.com
Arrival-Date: Fri, 8 Apr 2016 10:12:19 -0400 (EDT)

Final-Recipient: rfc822; thirdparty@thirdparty.it
Original-Recipient: rfc822;thirdparty@thirdparty.it
Action: failed
Status: 5.0.0
Remote-MTA: dns; mail.thirdparty.it
Diagnostic-Code: smtp; 550 Your server IP address [1.2.3.4] is missing a
reverse DNS entry. See
http://spamauditor.org/best-practices/check-ip-reverse-dns/ for more
information. Protection provided by MagicSpam 2.0.0-1
http://www.magicspam.com

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