Office 365 Error - DNS Lookup Failed

I have a couple of users that lose their connection to Exchange online/Office 365. They lose their connection via Outlook and also the web app. Outlook says "Disconnected" and the Web App throws a "DNS_PROBE_FINSIHED_NXDOMAIN"  error:
Chrome Error Snip.

A simple reboot fixes the issue but I cannot have my users rebooting all day. This is a recent issue and so far Microsoft Support does not have an answer for us.
We are running Windows 7 Pro. We had McAfee but removed in attempt to identify the culprit but that did not fix the issue. We have recently replaced our firewall but to take that out of the equation; I connected the pc to my mobile hotspot, completed dns flush, and disconnected cat 5 from NIC. Still having the same issue.

I have attached the event viewer details of the event as well as the message displayed by Google Chrome.

DNS-Issue-Office-365-6.10.15-OL.txt
unclevito101Asked:
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Zephyr ICTCloud ArchitectCommented:
Can you rule out DNS issues? Did you try using other DNS servers to see if that would help? I might be stating the obvious of course but we need to rule out as much as possible, maybe you already saw this page as well and tried the tips there?
unclevito101Author Commented:
Yes, I tried Open DNS, alternative DNS, and hooking it up to a mobile hot spot while the issue is occurring. We have an open ticket with MS but their only suggestion thus far was to disable IPv6.

No, I have not checked that page yet; so thank you. I am looking it over now. As far as stating the obvious; I agree that you have to start with that because sometimes we overlook the obvious and go right to complex solutions.

Thank you for the feedback. If I find the solution on the page you requested, I will make sure and provide an update.

Thanks again!
unclevito101Author Commented:
Also, we have now 3 users out of approximately 100 affected by this issue and it started about 2 weeks ago. Not sure if that helps at all.
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Zephyr ICTCloud ArchitectCommented:
Yes, it's a strange case ... Maybe the new firewall triggered something, but since you bypassed it already ... I'm interested to see if the ipv6 adjustment might help, or any of the other tips in the link.

Is there anything else you can remember from 2 weeks ago?
unclevito101Author Commented:
Not yet, and yes it is one of the stranger issues that I have faced... Hence, the EE post. We did try disabling IPv6 and one of the affected PC's failed out almost immediately. So, we are trying Windows updates but, in my experience they are more often the cause and not the solution. Anyway, one of the strangest parts of this is that when we lose connection to office 365; we still have full connectivity to every other website and network resource.

Please let me know if you think of anything at all. I am desperate at this point. I have read through the link you provided and have begun looking into those as possible solutions.
Zephyr ICTCloud ArchitectCommented:
I remember a problem facing Win7 clients regarding DNS and we needed to change following settings in order to solve it:

In an elevated command prompt:
netsh interface tcp set global rss=disabled
netsh interface tcp set global autotuninglevel=disabled
netsh int ip set global taskoffload=disabled

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In the registry:
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters]
EnableTCPChimney=dword:00000000
EnableTCPA=dword:00000000
EnableRSS=dword:00000000

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I think it's mentioned in the link as well ...

I'm remembering a case like this once though, it's coming back to me, in the end we gave up and re-installed the client, only to be facing the same issue again... I can vaguely remember to even try using the clients' host file.

Does it help to flush dns (ipconfig /flushdns) at the time the issue is happening?  I'll keep thinking.
unclevito101Author Commented:
Unfortunately not. I ran Winsock and thought that was the fix but it was the mandatory reboot after running Winsock that was the real fix.

Yes, I did see see these 2 items in the link you referenced initially. I am going to try them on our test pc today and will get back to you.

Thank you for the input.
Zephyr ICTCloud ArchitectCommented:
No problem, keep us posted!
unclevito101Author Commented:
We ended up resolving this by implementing a firewall traffic over for the affected users over ISP 3 & 4. ISP 1 & 2 is where the primary load balancing takes place. We use open DNS on firewall for DNS 1 & 2 and ISP DNS on DNS 3. We had a name lookup issue with DNS 3, we changed it but don't think that resolved it but adding in MAC of affected workstations did.

Don't know, this is one that I will probably never figure out the why, just the fix. Thank you spravtek for your input, you were the only one that responded to this.

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Zephyr ICTCloud ArchitectCommented:
No problem, glad you found a solution in the end, I remembered another case where we even had this issue with a workstation that was using Google DNS servers directly ... Strange.
unclevito101Author Commented:
It was a fix provided by me but I never did figure out exactly what was taking place and the reason why the solution fixed it.
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