Confirmed, seeing it here as well.
https://xnnd.com/dns.cgi?t=a&d=mail-eopbgr660111.outbound.protection.outlook.com.&m=yes
(hit reload a couple times, you'll get different results, intermittent
servfails.

Trying it this way is interesting:
https://xnnd.com/dns.cgi?t=a&d=mail-eopbgr660111.outbound.protection.outlook.com&m=yeszone
Querying the authoritative servers sometimes works, sometimes doesn't.
I'm sure they have a big bunch of servers behind a load balancer and
as noted, some are probably misconfigured.

I've let various Microsoft people know.

Cheers,
Al Iverson

Cheers,
Al Iverson

On Tue, Aug 24, 2021 at 2:20 PM Nitin Agarwal via mailop
<[email protected]> wrote:
>
> We're seeing this as well. Here are some details/lookups on a sample Office 
> 365 ip:
> https://www.misk.com/tools/#dns/40.107.66.111
>
> Reverse dns is fine, forward lookup fails intermittently due to a nameserver 
> referral loop:
> https://www.misk.com/tools/#dns/mail-eopbgr660111.outbound.protection.outlook.com
> https://www.misk.com/tools/#dns/mail-eopbgr660111.outbound.protection.outlook....@ns1-gtm.glbdns.o365filtering.com
> https://www.misk.com/tools/#dns/mail-eopbgr660111.outbound.protection.outlook....@ns2-gtm.glbdns.o365filtering.com
>
> Keep hitting refresh and you'll see the issue. Eventually, their auth servers 
> return an ip. Looks like one or more (but not all) of the auth dns servers in 
> their dns farm is misconfigured, which is why it is intermittent.
>
> You can also run dig multiple times from your local machine and you can see 
> it there as well:
> dig mail-eopbgr660111.outbound.protection.outlook.com 
> @ns1-gtm.glbdns.o365filtering.com
> dig mail-eopbgr660111.outbound.protection.outlook.com 
> @ns2-gtm.glbdns.o365filtering.com
>
> If anyone has a contact there on the right team, please forward.
>
> Thanks,
> Nitin Agarwal
> [email protected]
> https://www.misk.com/
> https://www.misk.com/tools/
>
>
> -----Original Message-----
> From: mailop <[email protected]> On Behalf Of Neil Youngman via mailop
> Sent: Monday, August 23, 2021 9:16 AM
> To: [email protected]
> Subject: [mailop] Microsoft RDNS issues
>
> Is anybody else seeing issues with some Microsoft RDNS failing 
> intermittently. I'm seeing RDNS failures in our Exim logs, but when I check 
> the IPs from the command line, there are no obvious issues and it isn't 
> affecting all our traffic from Microsoft.
>
> It seems t have started a little before midnight on Friday.
>
> I'm not seeing anything similar with mail from Google or Messagelabs, which 
> is why I think it's somewhere external to us.
>
> Neil Youngman
> Neil Youngman
> Developer
>
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-- 
Al Iverson // Wombatmail // Chicago
Deliverability: https://spamresource.com
DNS Tools: https://xnnd.com
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