Outlook connects to Office 365 Mailbox bypassing Autodiscover

Microsoft has added a new feature called Direct Connect starting with Outlook 2016 version 16.0.6741.2017 and all later versions. Its now by-default behavior of Outlook 2016 to automatically connect to Office 365 User Mailbox no matter Auto-discover records are pointing towards other exchange hosting provider.

In Outlook 2013, there was a manual configuration feature which helped admins or end-users to configure the profile with manual settings according to the email hosting provider. However, after upgrading from Outlook 2013 to Outlook 2016/2019, the end-users don’t find this manual configuration feature which in turn causes great difficulty as it tries to connect to Office 365 rather than connecting to their old email hosting providers.

The Direct Connect feature in Outlook 2016 connects the profile to Office 365 only when the user mailbox (been used at other email hosting provider also) have the same set of credentials created in Office 365 with valid Exchange Online License. This issue is mostly experienced during the time of Migration to Office 365 when exiting Office 2013 Suites are also upgraded to Office 2016.

Before migration, the end-users are mostly created manually or in bulk by Global Administrators in Office 365 to provision their mailboxes so that the old email hosting provider email data can be copied inside it. Users have a mailbox in Office 365 except the fact they can’t receive the emails until Mx Record is changed and pointed towards Office 365.

When the Issue arises?

During upgrade from Outlook 2013 to Outlook 2016, when Global Admin or end-user tries to configure an Outlook profile to connect to their existing email hosting provider, Outlook 2016 configures the profile by looking for user mailbox present in Office 365.

Eventually, it creates difficult situation on how to access emails present at old email hosting provider. So, let’s quickly check the easy way out to use Outlook 2016 to access emails present at an old email hosting provider.

We can easily disable the Direct Connect feature present in Outlook 2016 via registry. It can be done manually on a per-machine basis and also via Group Policy if required to be applied to group of machines joined to the company domain.

Prevent Outlook 2016 from connecting to Office 365 by simply adding a registry key.

Open Regedit and add the below DWORD value to the location:

DWORD: ExcludeExplicitO365Endpoint
Value = 1

Don’t forget to restart the machine after this change as registry doesn’t refreshes the change automatically. After restart, configure the new profile and this time it will bypass the O365 Endpoint, check the Auto-Discover record which is still pointing towards old email hosting provider and will fetch the correct settings from the old email hosting server.

Verify Outlook 2016 is connected to old Email Hosting Server or Office 365:

a) During configuration of User Profile from Mail option in Control Panel, if it gives a Microsoft Popup to enter the credentials, it means it’s trying to connect to Office 365, stop proceeding. Follow the above registry key method, verify it, restart and then re-try.

b) After the profile gets configured in Outlook 2016, look at right bottom corner (near the time on the screen) in the Notification Area for tiny Outlook icon, hold down CTRL + Right Click on it and select Connection Status. It will show to which Server Outlook 2016 is connected.

If it’s connected to your old email hosting server, you will see its server address, however, if it’s connected to Office 365, it may show you https://outlook.office365.com/mapi/

Thanks a ton for reading my above blog. If you have any comments, suggestions, or feedback please spare a second to post it.

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