Skype for Business O365 DNS configuration

We are implementing Skype for Business O365.  I configured External DNS (Go Daddy) with an appropriate CNAME and SRV records  for Skype for Business O365.  Externally (outside of my office network), I am able to connect to Skype but I can not connect in the office. it says that Server is unavailable after typing a password.

In the office we have Windows Server 2012 DNS server  (split brain DNS) for our domain.

How should I configure my internal DNS to make it work. I tried to configure My internal DNS exactly as external but for some reason it does not work.

Please let me know if you have ideas why it does not work internally (in the office network).
Tech ManInformation TechnologyAsked:
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Olgierd UngehojerSenior Network AdministratorCommented:
Do you have the same domain on GoDaddy Dns and on local domain controller or you have some sub domain for domain controller ?
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Tech ManInformation TechnologyAuthor Commented:
I have the same domain goDaddy and Internal DNS server . I have split brain configuration.
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maredzkiCommented:
If your dns records are correct on both internal and external dns of the same zone and a i.e. laptop works while outside of office but not while in the office, you might be looking at a web filter/firewall blocking the traffic.
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Olgierd UngehojerSenior Network AdministratorCommented:
maredzki is right, next step is to check firewall port configuration . This list of ports what you have to allow on firewall:
https://support.microsoft.com/en-us/help/2409256/you-can-t-connect-to-skype-for-business-online--or-certain-features-do
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Tech ManInformation TechnologyAuthor Commented:
Great, I think that was the problem (THANK YOU SO MUCH). I made some modifications in My firewall it fixed the problem. But for some reason on my computer, i cant connect to Skype anymore. I tried different accounts and they don't work.
This is what I get only on one computerI tried my account on another computer and it worked. It was working fine but after I switched VPNs multiple times stopped working

I tried to clear credentials cache, also cleared dns - no luck...

Any ideas to troubleshoot it ?
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Olgierd UngehojerSenior Network AdministratorCommented:
What kind VPN are you using, PPTP, IPSec ? Do you have configuration gateway-to gateway or client-to-gateway ?
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Tech ManInformation TechnologyAuthor Commented:
Sorry for the late response. It was just regular client to network VPN.
I tried my account on the different computer in the same network and it worked but not on this computer.
I also tried to clear all cached folders and credentials but still no luck.
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Olgierd UngehojerSenior Network AdministratorCommented:
Try to open computer management and go to deice manager. In a view mane choose show hidden devices and remove WAN mini  (PPTP) interface, then restart computer, install WAN Miniport and try to setup PPTP tunnel again.
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Tech ManInformation TechnologyAuthor Commented:
No luck on recreating PPTP.
At this point thinking to re-install OS.
Tried everything
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