How is Reverse IP, PTR, rDNS configured on a home server?
 

Hello, I am somewhat confused with Reverse IP, PTR, rDNS and I have these questions:

1. Do I need to configure the PTR?
2. How should I configure the PTR?
3. Can I configure it on the router?
4. Should I call the internet provider?
5. Can I configure it with the domain name provider (Godaddy)?


I have in my house:

- Raspberry Pi 4 4GB
- Raspbian Lite (SSH)
- LAMP configured
- Postfix configured
- SSL configured
- Godaddy (domain.net) ==> https://mail.domain.net
- DMZ configured router and open ports (I have access to the router)
- MTA-STS, DMARC, DKIM, SPF, X509, CA, StartTLS, configured well
- The emails work perfectly, I receive and send perfectly


Internet - Router - Raspbian

Example with name and fictitious number:

With the test I only see the name of the internet provider.

But I don't know where or how to configure the PTR on a "home server" test?


Thank you

DNS records for a domain are maintained in the authoritative name server for that domain.
Probably that's a GoDaddy name server, but it wouldn't have to be.

will return lines that identify the authoritative name server

The PTR for which name?
Might be needed for email depending on your mail configuration.
In a DNS server.
Check your router's manual.
What for?
If you need a PTR record for this name, call GoDaddy.
What is your problem?
What do you mean by "home server test"?
One does not configure PTR on a test. One configures it on a DNS server.

I got the domain in godaddy and everything points to the "server", everything works fine, but I don't know how to configure the PTR or reverse IP

Godaddy:

Our administrators configure reverse DNS on all of our email servers. If you administrate your own server, you can contact your IP address's provider to configure reverse DNS.

Note: Do not use a PTR record to configure reverse DNS in our system.


If I understand correctly the PTR is configured on the server?

I'm confused

deleted

Who is your IP address provider...that is, where is your domain hosted?

Again, all DNS entries, including any PTR records, for a domain are configured on the authoritative name server for the domain. In your case, that’s domaincontrol.com. That does not tell us what Your domains IP is...that is defined in the domaincontrol.com name server.
That’s also where the reverse (rDNS) is defined. You’ve said there is an rDNS record, and your email is working. There is no requirement, or need, for the name on the rDNS record to match the domain name...only that there is one for the domain’s mail IP.

Looks like domaincontrol.com is GoDaddy. If you don’t know how, or have access to, the name server settings for your domain, you need to contact GoDaddy support.

What do you think you need a PTR record for?

Thanks for the reply.

I see that the PTR is a requirement for some accounts to verify that the mail is authentic, even some services such as hotmail or company emails do not receive the mail or reach spam.

The domain is hosted on Godaddy, but I don't have access to configure the PTR. Is it configured in DNS as TXT?

With host 200.210.60.50 I get in the answer the name of the company that distributes the internet in my house = th.internetprovider.net

50.60.210.200.in-addr.arpa domain name pointer d200-210-60-50.th.internetprovider.net.

So to understand, the PTR must be configured by Godaddy, but if it is not so necessary, I can simply not configure it.

After all it is a small "server" for two personal email accounts.


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Note: Just as a note, separately I have another server with another domain with a VPS provider and I can configure the PTR without problem and the DNS stays in Godaddy.
But with this home server I don't know how or where to configure the PTR.

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Thank you very much

PTR is one type of DNS record...TXT is a different kind.
If you’re talking about SPF records, those are TXT records.
Again, all DNS entries for a domain are configured on the authoritative name server for the domain.

Don’t confuse the registrar with the name server. They don’t have to be the same.
Whois of the VPS domain will tell you what name server it’s using.
dig domain.com will tell you the IP address for the domain

If the Reverse response is not provided by your name server, you'll need to contact your ESP to help you set a PTR record.

One clarification to my earlier comments. A rDNS record is controlled by the provider of the IP address, not by the authoritative name server of the domain.

But, again, you've indicated there is an rDNS record for your IP address, so you're covered.

I would also like to stress the the reverse DNS is often configured on a completely different server/provider than the other types of records (A, MX, whatever). Only the internet provider who owns the IP subnets can offer a PTR record.

Having a PTR record itself is not enough for a proper e-mail configuration. It would also need to point to the domain presented in the EHLO command. This is the first SMTP command that an MTA uses to identify itself. A lot of ISPs automatically allocate PTR records to their clients (to be honest, I'm not sure exactly how they make use of that further on - e-mail sending is obviously not what they have in mind), but the existence itself of such a record does not guarantee that your e-mail is going to pass the Reverse DNS verification, which is quite standard for e-mail servers - so you should definitely have a PTR record. Some E-Mail providers (for instance IONOS/1&1, in my experience) reject e-mails automatically if you don't it.

Thanks for answering.

I am a little confused but I am understanding the following:

1 -Godaddy (Provider of the domain) here the DNS is configured (MX, A, NS, SOA, CNAME, etc) I understand this.

2 -As an example: I understand that if my server was in a VPS, the rDNS or Reverse IP is configured in the VPS and not in Godaddy.

3 -My situation: I am configuring my server at home (I have a static IP), this means that in order to configure the rDNS or Reverse IP, I have to speak to my internet provider, which is the provider of the public IP? Is there no other method?

4 -PTR, rDNS and Reverse IP is the same?

Results:


user@debian:~$ dig -x 200.100.50.5

Code:

---

; <<>> DiG 9.12.5-P4-5.1-Debian <<>> -x 200.100.50.5
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 52334
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0

;; QUESTION SECTION:
;5.50.100.200.in-addr.arpa.    IN      PTR

;; ANSWER SECTION:
5.50.100.200.in-addr.arpa. 37702 IN    PTR    d200-100-50-5.yt.northwestel.net.

;; Query time: 3 msec
;; SERVER: 192.168.1.1#53(192.168.1.1)
;; WHEN: vie abr 24 16:12:44 PDT 2020
;; MSG SIZE  rcvd: 91

---

user@debian:~$ host 200.100.50.5

Code:

---

5.50.100.200.in-addr.arpa domain name pointer d200-100-50-5.yt.northwestel.net.

---

user@debian:~$ host domain.com

Code:

---

domain.com has address 200.100.50.5
domain.com mail is handled by 5 mail.domain.com.

---

Router:
Attachment 33078


Thanks

Again, you have a reverse DNS:
It is not necessary that the rDNS reflect your domain name, just that it exists. The one you have is completely accurate.
The IP belongs to nortwestel.net, and that's what it says.

If you want it to reflect your domain name, yes, you'll have to contact northwestel and ask them to change it. They may do that, since it's a static IP, but it's not necessary, IMO.

1. Correct
2. rDNS is configured by the company/ISP that "owns" the IP address. In your case, your ISP
3. see above, and answer to #2
4. rDNS == Reverse IP == Reverse DNS. PTR records can be used for other things besides rDNS, in which case, they'd live at GoDaddy, with the other domain related records.

Excellent, thank you very much for answering, now I understand.

Cheers