The default Mail Client in Windows 10 is Windows Mail. When users click a mailto protocol, this opens up Windows Mail App, and some users end up creating mail profiles on the Windows Mail App. This can cause some confusion as we are using Outlook.
Microsoft is pushing users to use Windows Mail as opposed to Outlook. Outlook is better suited for business needs. This article will explain how to make sure that when you click a mailto link, your system launches Outlook instead of Windows Mail.