Sending, receiving, and organizing email in Outlook.com
This usually means the reading pane is turned off in Outlook on the web or Outlook.com.
Turn it back on:
- Open Settings.
- Go to Mail > Layout.
- Under Reading pane, select Right or Bottom.
- Save the change and refresh the page.
After that, a single click should open the email in place instead of requiring a double-click to open it in a new window.