Using the preview pane
The preview pane makes it so that you can view a message without opening it fully - it is what makes Outlook appealing to many users. In order to utilize this function, you have to Enable it.
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- Open your Gmail Settings
- On the Labs tab, scroll down to Preview Pane and click Enable.
- Click Save Changes.
- Gmail will reload. Once it reloads, you will see a new button called Toggle split pane mode to the left of Settings.
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You can choose between No Split, Vertical Split (like Outlook), or Horizontal Split