Unable to create A DNS record with underscore in Plesk: The specified domain name is not valid. You need to specify a valid domain name like domain.co

[Carl Swart]

Username:

TITLE

Unable to create A DNS record with underscore in Plesk: The specified domain name is not valid. You need to specify a valid domain name like domain.com.

PRODUCT, VERSION, OPERATING SYSTEM, ARCHITECTURE

Version 18.0.53 Update #2, last updated on June 29, 2023 11:22 AM, CentOS Linux 7.9.2009 (Core)

PROBLEM DESCRIPTION

I am unable to create NS records that use an underscore (_). _domainkey.example.com NS ns1.example.com.
Please see help desk article: https://support.plesk.com/hc/en-us/...-specify-a-valid-domain-name-like-domain-com-

STEPS TO REPRODUCE

Log into the control panel, go to any domain, click on the DNS icon to open the DNS manager. Try to add a record of type NS, where the host starts with an underscore (_)

ACTUAL RESULT

Error is produced and the record is not added.

ERROR: The specified domain name is not valid. You need to specify a valid domain name like domain.com.

EXPECTED RESULT

The record must be added as per RFC 2181, which states: "
Similarly, any binary string can serve as the value
of any record that includes a domain name as some or all of its value
(SOA, NS, MX, PTR, CNAME, and any others that may be added).
Implementations of the DNS protocols must not place any restrictions
on the labels that can be used. In particular, DNS servers must not
refuse to serve a zone because it contains labels that might not be
acceptable to some DNS client programs.
"

ANY ADDITIONAL INFORMATION

Please see https://support.plesk.com/hc/en-us/...-specify-a-valid-domain-name-like-domain-com- for my comments.

YOUR EXPECTATIONS FROM PLESK SERVICE TEAM

Help with sorting out

 

[Maarten.]

Unless I misunderstood your problem description:
You're trying to add a domainkey as an NS-type record. The domainkey should be added as a TXT-type record.

 

[scsa20]

I will also add that the only time I've seen underscores as NS records is in a Windows Server domain environment but that's because Microsoft uses them internally for a lot of the domain services and is not used on the public DNS for the NS record types.

 

[Kaspar]

@scsa20 there are some useful use cases for using a underscore in a NS record: Forwarded to devs - Unable to create NS records with underscores

 

[Carl Swart]

The domainkey should be added as a TXT-type record.

I 100% agree with you, yet, you get responses like this:

Thanks for getting in touch.

So the _domainkey NS records are subdomain NS records that allow us to host DKIM keys on
behalf of the client.

There are about a handful of hosting providers in the world that doesn't allow for
additional NS records to be added.

Aren't you able to add these records in?

Now, I immediately respond to such a statement "about a handful of hosting providers" as utter nonsense, since there are many more than a handful of providers using Plesk.

So the solution provider has this convoluted way of creating a _domainkey.domain.tld sub domain and then serving the sub domain from their DNS servers, which is why you need the underscore (_) in the NS records.

I re-iterate my initially statement .... I think Plesk is not quite RFC 2181 compliant, but I am no expert.

 

[Carl Swart]

@scsa20 there are some useful use cases for using a underscore in a NS record: Forwarded to devs - Unable to create NS records with underscores

Ahh, thank you for pointing that out!

Now, I just hope it will get fixed sooner than later. It has been an issue for going 3 years.

 

[scsa20]

@scsa20 there are some useful use cases for using a underscore in a NS record: Forwarded to devs - Unable to create NS records with underscores

In your example afaik Let's Encrypt no longer uses NS records for the ACME-Challenge and instead uses a TXT record now. So it's a moot point at this point. I don't really see what some of the use cases are to use an underscore as a starter for NS servers for the public DNS. If private DNS then sure, not for public though.