Allow Basic Authentication prompts from network proxies

This policy setting controls whether network proxies are allowed to show Basic Authentication prompts. By default, all Basic Authentication sign-in prompts are blocked, and the user is shown a message that the sign-in method isn’t allowed. If you enable this policy setting, then network proxies will be allowed to show Basic Authentication prompts. Warning: Allowing Basic Authentication sign-in prompts isn’t recommended because it’s a security risk. If you disable or don’t configure this policy setting, all Basic Authentication sign-in prompts from network proxes will be blocked, and the user will be shown a message that the sign-in method isn’t allowed. Note: This policy setting only applies to subscription versions of Office, such as Microsoft 365 Apps for enterprise, and to subscription versions of Project and Visio. For more information, see https://go.microsoft.com/fwlink/p/?linkid=2199001.