Microsoft has introduce an Autodiscover lookup function in certain Outlook 2016 products that will attempt to automatically configure an Exchange account associated with the Office license email address or with an outlook.com hosted address. This can cause users to see issues in their Outlook client including username/password errors, unexpected From addresses appearing in their outbound email, or Autodiscover certificate errors.
The attached patch below will restrict Outlook's Autodiscover lookup method to prevent Outlook from autoconfiguring Outlook.com accounts and Office license associated addresses. The patch will also provide a slight speed increase during the Autodiscover lookup process. We recommend applying the patch to the registry of any PC running Outlook 2016.