Outlook 365 not connecting to on-prem Exchange

Occasional Contributor



in an effort to switch to a shared licensing model, we are re-deploying Office 365 via ODT.

However, after re-deploying it, Outlook just will not connect to our on-prem Exchange server but instead connects to Exchange online. 

The attached "ODT 365.zip" file contains the two files:

  • configuration-Office.xml | This one was used initially, everything works fine and Outlook connects to the on-prem Exchange without issues. However, it's not shared licensing.
  • configuration-Office365Shared.xml | Everything but Outlook not connecting to on-prem works fine as well.

We've already tried the registry fix mentioned here: https://techcommunity.microsoft.com/t5/office-365/outlook-365-outlook-install-does-not-see-local-exc... 

>> HKEY_CURRENT_USER\SOFTWARE\Policies\Microsoft\office\16.0\outlook\autodiscover
DWORD: ExcludeExplicitO365Endpoint
Value = 1


However, that registry key does not exist in our environment. There was mentioning of a different path in the registry somewhere (can't find the link anymore), but those paths did not exist in our registry either. 

We also tried manually adding the on-prem server by manually setting up an account in Outlook. This did not work either.


So how do we manage to get Outlook 365 to connect to our on-prem Exchange server when installing it with the shared license option? We do not have a hybrid model yet and are not using Exchange online yet. 



I should have mentioned this is in a VMware Horizon Instant Clone environment. 





2 Replies
I believe I found the issue...will do some more testing to be sure and update this thread accordingly.

The solution/workaround in our case was to disable the 'Exchange Online' app in the users licensing tab:


As soon as that checkbox is unchecked, Outlook will connect to the on-prem Exchange. 

This works for now. However, it would be convenient if this could be disabled at a group or license level, instead of having to go into each users settings and disable it. Perhaps there is an easier way?