In Windows 10, the Tasks experience in Outlook.com (powered by ‘To-Do’) means that when looking at your inbox, you can save time and create tasks by dragging and dropping an email to your task list. You can also easily schedule items by dragging a task to your calendar. Your tasks then travel with you on the To-Do app.
You can see how it’s done on the Windows Blog here:
Go to https://blogs.windows.com/windowsexperience/2018/12/16/windows-10-tip-schedule-items-by-dragging-a-task-to-your-calendar/#WX3WrBWATdGxSk48.97