Disabling Autodiscover for Microsoft 365 in Outlook

This article explains how to disable Autodiscover for Microsoft 365 in the Windows Registry. This is necessary if you are using a Hosted Exchange mailbox with IONOS or your own on-premises Exchange server. This will prevent Outlook from constantly attempting to log in to the domain registered with Microsoft 365.

When is this adjustment required?

If you notice one or more of the following symptoms in Outlook, it is very likely that you will need to adjust the Autodiscover settings:

Note regarding a temporary mailbox: When Outlook starts, a dialog box appears informing you that your mailbox has been temporarily moved to the Microsoft Exchange server.

Error message ‘Name does not match’: You will see an error message stating: ‘The name does not match any name in the address book.’

Cryptic email address: In the folder pane on the left-hand side of Outlook, an automatically generated, cryptic name is displayed instead of your usual email address (e.g. starting with outlook_). This is a clear indication that Outlook has been redirected to a Microsoft 365/Outlook.com endpoint.

Note

The error message “Name does not match” and the reference to a “temporary mailbox” may, in some cases, have other causes (e.g. server outages, general connection problems or a corrupted Outlook profile). The cryptic email address, on the other hand, is a reliable, specific indicator of the problem described here.

Customise the Microsoft Windows Registry

If you are experiencing the symptoms described, or if you wish to disable Autodiscover altogether, follow the steps below.

In the search box on the taskbar, type regedit and press Enter.
In the Registry Editor, select the following key from the navigation pane on the left: \HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Outlook\Autodiscover
Right-click the key.
Click New > DWORD (32-bit) Value. The DWORD value will be created.
Name the DWORD value as follows: ExcludeExplicitO365Endpoint
Double-click the newly created DWORD value. The Edit DWORD (32-bit) Value window opens.
Enter the value 1 in the Value field and click OK.
Create another DWORD (32-bit) Value.
Name the DWORD value as follows: ExcludeHttpsRootDomain
Double-click the newly created DWORD value.
Enter the value 1 in the Value field and click OK.
Close Outlook and then reopen the program.
If you have already set up a profile and, where applicable, an email account, you will need to set these up again.

The Autodiscover feature for Microsoft 365 has now been disabled.

Please Note

If you have already used the email address for your Microsoft Exchange email account to register with Microsoft 365, we recommend that you change this email address. If the email addresses are the same, the setup may fail due to conflicts.