Computer Configuration > Administrative Templates > Microsoft Edge - Default Settings (users can override)
Both
HKLM\Software\Policies\Microsoft\Edge\Recommended
OBSOLETE: This policy is obsolete and doesn't work after Microsoft Edge 105. This policy doesn't work because the Outlook menu is now contained within the Edge Sidebar and can be managed using the 'HubsSidebarEnabled' (Show Hubs Sidebar) policy. This policy is used to manage access to the Outlook menu from Microsoft Edge. If you enable or don't configure this policy, users can access the Outlook menu. If you disable this policy, users can't access the Outlook menu.