Outlook 2016 not connecting to exchange 2013 server after closing and re-opening, however, outlook 2013 successfully connects each time.

Hello Experts. In my test env, i have exchange 2013 enterprise installed with both mb, and cas installed on all exchange servers, with AD 2012 R2. On the domain joined win 10 client machines, outlook 2013 connects fine each time to exchange using HTTP with NTLM auth.

However Outlook 2016 v16.0.4266.1001 is unable to connect with HTTP with NTLM. I am able to successfully build users outlook profile in outlook 2016, it connects to exchange server, am able to send emails, however, when i close and reopen outlook 2016, it continuously prompts for user credentials, and does not accept them. So Outlook 2016 goes in disconnected mode. When i delete the users mail profile, and reconfigure, outlook 2016 successfully connects, but when outlook 2016 is closed and re-opened, same issue. This does not happen with outlook 2013.

I've run autodiscover tests via testconnectivity.microsoft.com, and the 'test outlook autoConfiguration, all tests pass successfully with no errors. From the client machines, i am also able to successfully ping the autodiscover.company.com url and all exchange and AD servers . In our production, we have the same setup, with outlook 2016 v16.0.4639.1000, and all works fine. Autodiscover resolves to our load balancer, which forwards the connection to any exchange server. Has anybody encountered this issue with this version of Outlook? Please let me know.

 Thanks in advance.
Newguy 123Asked:
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Amit KumarCommented:
I think this is happening because Outlook 2016 is default enabled with ADAL authentication.

Try disabling it with a registry key:

Have you tried to install latest service pack of office 2016?
Todd NelsonSystems EngineerCommented:
Do you have MAPI over HTTP enabled?  If not, you might want to.

Additionally, try restarting the autodiscover app pool on the Exchange 2013 server.

Restart-WebAppPool MSExchangeAutodiscoverAppPool

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