Outlook 365 not connecting to on-prem Exchange

Copper 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. 





3 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?

@st84 Sorry guys for replying to an older thread but we have right now exactly the same issue. We have with the mail account online exchange deactivated AND did the Reg edit workaround but still the pc is not connecting to our on premise exchange server. Any other ideas?