Microsoft Outlook and some web email clients (like Yahoo! Mail and Hotmail) support a tri-pane design – the folders appear in the left sidebar, email messages are at the center and then there’s a handy reading pane that you can add to the right side of your messages or at the bottom (see the screenshot above).
The reading pane is useful because you can quickly preview the contents of your email messages without having to actually open them thus saving you some time.
Gmail doesn’t have a standard reading-pane but they’ve added something similar called “Sneak Peek” that also lets you preview messages in your mailbox but with a simple right-click. You can think of Sneak Peek in Gmail as a floating reading-pane that can be activated on-demand – see screenshot.
To enable this feature in your Gmail or Google Apps for Gmail account, hit the Labs icon, search for “Message Sneak Peek” and select “Enable.”
You can view any email message with a right-click but this feature won’t work inside the “Spam” folder though it works for Trash.
If you don’t plan to add this feature to your Gmail mailbox, you can still view emails without changing the current view – just hold the Shift key while clicking on any email message and it will open in new window.