I got a new laptop. I have been using WIN 7 with Outlook Mail app and now WIN 10 with Windows Mail App.  My email messages remained in the viewing pane until I deleted them in Outlook.  Now in Mail they disappear from the viewing pane in a couple of days on their own .  This is very disconcerting for me as I typically leave messages, some for a really long time, in that pane.  I cannot figure how to keep these messages.  There must be some way to tell the app not to delete my messages????