Seems a bit mysterious - but why not just change DNS? This could just be a temporary measure - you could pay for DNS hosting (which is inexpensive) or use a service like Cloudflare who demand you change to them.

Otherwise, troubleshooting DNS can become a little involved. Is there any more info from Google? Do you know if it is a problem contacting your name servers or with retrieving the relevant records?

You can check that the records are OK, but what about the servers? Take the errors seriously and set up different (or secondary) nameservers. I use Route53 myself but there are plenty of free and reliable hosted DNS services as well. Also consider a DNS monitoring service.

Thanks a lot lads, but why changing the infrastructure when 4 domains are doing fine since ages with exactly the very same settings ... ? Any idea on how to contact Google apart from posting at their useless forums?

Trying to fix it yourself will, at the very least, be quicker than getting Google to fix it. It's also a way to prove that it's a problem with them, which increases your chances of a permanent fix.

Like I said, the DNS settings may be fine, but there may be an issue with the nameservers not (properly) responding to queries. Apparently, Google has trouble fetching your DNS records, so the first thing I would have done is set up DNS monitoring and probably change the nameservers. Google can't solve it if the problem is on your end.

robzilla, every #*$! dns tool that you can find on the web including googleapps confirmes, that all dns entries are fine.

And WMT can even reach these domains as robots text and server connectivity are confirmed to be ok.

Also several other domains on the same server with exactly the very same settings show none of such issues.

.

Still doesn't mean the problem can't be with your nameservers. Change them and you'll know.

Are the DNS errors dated? Are they still occurring? Is the type of error specified?

What could be possibly be wrong with the nameservers when Google has no issues with 8 domains and calls 4 temporarily unavailable though connectivity and robots txt are fine for all 12?

Neither web host nor registry seem to have any clues after checking all dns records thoroughly ....

Well, ###, I thought there was going to be a pervasive google/DNS problem because a near-identical issue came up less than a week ago:
[webmasterworld.com...]
But it's the same person asking. Are the same sites involved? What's the difference between that thread and this one?

Things have gone worse Lucy, so i started a new thread seeking solutions. Meanwhile those 4 domains can no longer be found on Google.

Everyone seems clueless, from web host to registrar. No response from Google and nothing on their product forum.

Or you did not get the answers you were hoping for. Google is not going to fix your DNS errors, and if you don't try a change of nameservers (5 minutes work?) or answer my questions, I can't help you.

Just because your online tools are not reporting any problems now does not mean there were no problems when Google tried to resolve your domain name. Im presuming this is some sort of a shared hosting package?

Are these domains or subdomains?

Why changing nameservers that were doing fine since years for these real domains when all of a sudden WMT flags 4/12 for DNS errors? All 12 have the same records.
Google reads all 12 robots.txt well and confirms server connectivity.

Bing has no problems at all ?

Are these domains or subdomains?

Great question also do you have a wildcard *.domain.com in your dns records?

Open questions:

Is there any more info from Google? Do you know if it is a problem contacting your name servers or with retrieving the relevant records?

Are the DNS errors dated? Are they still occurring? Is the type of error specified?

Are these domains or subdomains?

do you have a wildcard *.domain.com in your dns records?

Do you have a wildcard *.domain.com in your dns records?

No

Are these domains or subdomains?

All 12 domains are old regular domains, no sub domains. 3 of them are several years old with exactly the same dns records since ever.
All were indexed well with a few hundred real content pages, original videos, photos and writing at Google

Is there any more info from Google? Do you know if it is a problem contacting your name servers or with retrieving the relevant records?

Are the DNS errors dated? Are they still occurring? Is the type of error specified?

Google fetch reports for 4/12 : temporarily unreachable but confirms, that server connectivity is given as well as that robots txt are available for all 12/12
DNS errors started in April .

Are all 12 on the same nameserver?

Is there a reason you won't change the nameserver?

As said,. All 12 on the same nameservers since years without any issues until this happened.

That's not a reason not to change the nameservers. They might have been corrupted or whatever, it's hard to tell. But if Google has encountered DNS errors since April and it's an ongoing thing, then changing nameservers is the simplest thing you can do that could possibly get your sites re-indexed, so I don't understand why you keep resisting it.

...temporarily unreachable but confirms, that server connectivity...

I asked about DNS errors. That doesn't sound much like a DNS error. More like your website or server configuration is blocking Googlebot for those domains (i.e. can resolve IP, can connect to IP, cannot access website). Post a screenshot of your (DNS) errors in Search Console, if you can.

Switch to cloudflare DNS and test.

Google YOURDOMAIN [SPACE] EXTENSION if you are not 1 or 2 you are deindexed.

Was already testing cloudflare on 2 of the affected domains since this afternoon, thanks.
And both are ok now ....

More like your website or server configuration is blocking Googlebot for those domains

Why for only 4/12 ... All the same settings.
Anyway, cloudflare seems to be a good solution, also improving the speed ...
Thanks a lot guys!

I'm glad you caved and solved the problem ;-)

Sorry to report, that joy was premature.

Google fetch can now connect to all 4 affected domains, but still 3 of them report DNS error.

And the one that shows no longer dns error has now robots txt error.

So, not even cloudflare dns seem to get accepted.

You should probably have another word with your web host, then.

In the meantime the 4 sites have at least gone back into the index, google fetch works, so that probably WMT might take another while to fix that for those flagged 3 domains.

Btw. been with that web host since 10 years with various projects. Very reliable and with some outstanding, speedy service and only 1 downtime. Very capable fellows.. .