Outlook bypasses AutoDiscover and connects directly to Office 365 mailbox

Starting in Outlook 2016 version 16.0.6741.2017, Microsoft has enabled a new feature called Direct Connect to Office 365. What this feature does is connect Outlook directly to Office 365 if Autodiscover is not working. This is great feature but a network hiccup may cause your mailbox to connect to Office 365 rather than your on premise Exchange, even with a valid autodiscover record.

For Direct Connect to take effect the user must have an active mailbox on Office 365 with a valid license. Typically Direct Connect would be a neat feature unless you are in the middle of a migration to 365, but a network hiccup could incorrectly connect you to 365 even though you have not completed your migration yet.

During 365 migrations Hosted Exchange or On-Premise, we recommend disabling this option from the user computer registry:

You can stop Outlook from checking Office 365 for settings by setting a registry key.

HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\AutoDiscover
DWORD: ExcludeExplicitO365Endpoint
Value = 1


Then restart your computer and it should stop trying to connect to Office 365. 

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