Disabling Office 365 Autodiscover – Exchange Self hosted

Outlook 2016 onward can disconnect from Ms Exchange Self hosted. Set this DWORD data to below to force Outlook NOT to call the Office 365 Config Service to retrieve appropriate Autodiscover URLs.

This is useful when you have an on-premises Exchange server and want to prevent Outlook from automatically discovering Office 365 settings.

1. 1. Disable Autodiscover SCP Lookup on Client Machines

   • Service Connection Point (SCP) is used by the Autodiscover service in an on-premises Exchange environment. You can disable it by using registry edits on client machines to force them to use specific settings instead of relying on Autodiscover.

   Registry Edit (Manual Configuration):

   • Open Registry Editor (Press Win + R, type regedit, and press Enter).
   • Navigate to the following path:
     HKEY_CURRENT_USER\Software\Microsoft\Office\<Version>\Outlook\AutoDiscover


     For <Version>, replace it with your Office version:

     • 16.0 for Office 2016 or Office 365
     • 15.0 for Office 2013
     • 14.0 for Office 2010
   • Add new DWORD entries and set the value to 1 to disable certain Autodiscover methods:
     • ExcludeScpLookup → 1
     • ExcludeHttpsRootDomain → 1
     • ExcludeHttpsAutoDiscoverDomain → 1
     • ExcludeHttpRedirect → 1
     • ExcludeSrvRecord → 1
     • ExcludeExplicitO365Endpoint → 1 (this blocks Office 365 endpoint)
   • Restart Outlook after making the changes.

   2. Modify DNS Settings

   If you’re running a self-hosted Exchange, ensure your local DNS is correctly set up to prevent Office 365 from resolving to Autodiscover via DNS.

   • Ensure your Autodiscover DNS records are pointing to your on-premises Exchange server instead of Office 365.
   • Remove any CNAME records for Autodiscover that point to autodiscover.outlook.com if you are not using Office 365.

   3. Modify Outlook Settings via Group Policy (GPO)

   If you need to apply this setting across many computers in your organization, you can create a Group Policy Object (GPO) to disable the Autodiscover SCP lookup.

   • Download the Office Administrative Template files (ADMX/ADML) from the Microsoft website.
   • Once installed, open Group Policy Management Editor and create a new policy.
   • Navigate to:
     User Configuration > Administrative Templates > Microsoft Outlook <version> > Account Settings > Exchange

   • Enable the policy to control the Autodiscover service, where you can specify what methods to disable (like SCP, HTTP redirects, SRV records).

   4. Configure Exchange Server to Prevent Office 365 Autodiscover

   If you’re running a hybrid setup, you can adjust the configuration on your Exchange Server to ensure Autodiscover doesn’t redirect to Office 365.

   • In your Exchange Management Shell, run the following command:
     PowerShell Code

     Set-ClientAccessService -Identity <ExchangeServer> -AutoDiscoverServiceInternalUri $null


     Replace <ExchangeServer> with the name of your Exchange server.

   Summary:

   • Disable Autodiscover methods via Registry or Group Policy.
   • Ensure your DNS settings are correctly pointing to the on-premises Exchange.
   • Adjust Exchange settings to prevent internal Autodiscover lookups that might lead to Office 365.

    

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