Here's the way to turn off the new 'focused' tab in your Windows 10 Mail App. According to Microsoft the Focused tab is supposed to read the content of the mail and display it in the Focused tab if it decides that it's information that you would want to read right away. It's a good idea, but it needs your help to make it beneficial to you.

 

So, here's how to manage your emails to make sure they go in one tab or the other.  Or, you can even turn it off if you just want to return to the normal Inbox.