I am using Windows 10. Until recently I used to be able to adjust the size of the message (preview) pane by grabbing the top line and moving it up or down the screen. From yesterday the message pane has taken up a permanent high position on the page so I can only see my first 10 or so emails in the Inbox. I can switch off the pane altogether through View. But I really liked it before when I could have a smaller pane. When I hover over the top line it shows an up and down arrow as before, but it won't move!!