Exchange 2016 Outlook clients will not connect and there's not inbound/outbound email

I have one that has me stumped. A new customer has a DC and an Exchange 2016 server. Everything has been working fine until yesterday. Something happened and the server now will not let any of the Outlook clients connect. I can connect through OWA but I cannot send or receive emails. When trying to send, I get the You don't have permission to perform this action. Everything looks normal in the EAC. In the Event logs I am getting the 9041 which from reading on it points to DNS but the only DNS entry in the NIC configuration is the DC. Needless to say the customer is anxious to get email back up. Any ideas?
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Jose Gabriel Ortega CastroCEO Faru Bonon IT - EE Solution ExpertCommented:
To start check:
1. Exchange Server services, (everything that has Microsoft Exchange Server on it): Check if they are all on (especially those that are set to "automatic". If they are just reset the services.
2. DNS: Make sure that the "" it's set in place.
3. Check the entry points into your exchange server
You can use my script:
with the option -get (.\setall.ps1 -get)

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DP230Network AdministratorCommented:
use this tool to check your mail  server and domain:

then post the results and we can check further

Also, make sure that:
- SPF, MX, A, autodiscover records are correct
- Exchange services are running
- On EAC, Server -> Outlook Anywhere, there are correct settings
Jose Gabriel Ortega CastroCEO Faru Bonon IT - EE Solution ExpertCommented:
DP230Network AdministratorCommented:
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