Question Proper rDNS records for multiple domains under same IP

[yiannisf]

Hello all!

I am dealing with a very annoying problem lately, which has to do with emails sent from my server being rejected. In the logs I get an error that the connection was rejected as a Reverse DNS for my IP does not exist.

Indeed, doing an online reverse DNS lookup for my IP returns nothing.

Now, I am pretty sure that this started when I added some more domains on my Plesk, which all share the same IP address. Until then I only had one domain, and never had a problem with rejected emails.

So let me get more specific. My IP is 185.4.135.178 and the main domain is wondergreece.gr. Under the DNS settings of this domain there is a PTR record for the IP 185.4.135.178/24 to the wondergreece.gr domain. This has always existed there.

I then added some more domains, e.g. antilalos.gr, moorea.gr, etc. None of the new domains have a PTR record.

Also the Full hostname under the Tools & Settings/Server Settings is set to wondergreece.gr.

Could please someone identify if there is an obvious error on the above configuration. For example, I find it very awkward that although there exists a PTR record, the Reverse DNS returns nothing. Do I need to remove the PTR completely? Do I need to add a PTR record to every single domains, and if I do, where should they point? Is it something completely different?

I am pretty sure that this has already been discussed, but I did a lot of research and nothing I found could help me understand what needs to be done.
Please excuse my asking such rookie questions, I know they may sound "stupid" to most of you, but I am just starting with my DNS journey and I feel a bit lost so far...

Thank you in advance!

 

[mow]

Probably only forward lookups are delegated to your server, so you have to set the reverse DNS somewhere in your provider's hosting settings.

 

[weltonw]

The rDNS for an IP is set on the IP AuthNS, which is almost always controlled by your network provider. You'll need to contact your host and have them change the rDNS record.

The rDNS doesn't apply to the sending domain, rather the host name of the server.

If the hostname is wondergreece.gr, then the rDNS for the IP should point to wondergreece.gr

 

[Kaspar]

Reverse DNS is actually the opposite of a regular A type (or AAA type) DNS record. With a regular A type DNS record you point a host/domain to an IP address. So in your case the host wondergreece.gr points to IP address 185.4.135.178. rDNS does the opposite, it points a IP address to a host. For this PTR type records are used. This where it can get a bit confusing, because you can create PRT records in Plesk. But (in almost all cases) this won't do anything for you.
Thats because only the actual IP address owner can manage the reverse DNS. You are (most likely) just a user of a IP address, owned by your provider.

So you'll have to set the reverse DNS trough your provider. Usually they provide some control panel for this (basically what @mow also wrote).

You only need to define the reverse DNS for the hostname of your server. Not for individual domains. It is however a good practice to not use a full/main domain name as the hostname of your server. Rather use a subdomain as the hostname for your server. Something like controlpanel.mydomain.com.

 

[mow]

You only need to define the reverse DNS for the hostname of your server. Not for individual domains.

... unless you have more than one IP on the server, then those extra ones should have a rDNS matching the domain they're assigned to.

It is however a good practice to not use a full/main domain name as the hostname of your server. Rather use a subdomain as the hostname for your server. Something like controlpanel.mydomain.com.

But if you have a mail server on the machine, the rDNS for the IP you're sending on must match the domain the mail server is using. Which is not necessarily the (plesk) hostname of the server.

 

[yiannisf]

... unless you have more than one IP on the server, then those extra ones should have a rDNS matching the domain they're assigned to.

But if you have a mail server on the machine, the rDNS for the IP you're sending on must match the domain the mail server is using. Which is not necessarily the (plesk) hostname of the server.

As a matter of fact I do have a mail server on the machine. The host of the mail server is set to be mail.wondergreece.gr. The plesk hostname is currently set to wondergreece.gr. Should I ask the provider to set the rDNS to mail.wondergreece.gr or wondergreece.gr?

Thank you all very much for all the support!

 

[weltonw]

You set the rDNS to the hostname that postfix is using. This isn't always the hostname of the machine. See: Postfix Basic Configuration (myhostname)