Google recently rolled out a new option in Gmail Labs that lets users enable an Outlook-esque preview pane on their Gmail interface. With the feature enabled, you can simultaneously preview emails while reading or replying to others.
On the right of this preview pane, Gmail has a sidebar with “People” widget – which shows the sender’s details – and advertisements below it. If you don’t find this sidebar useful or consider it a waste of screen space then install ‘Gmail Preview Pane Extend’ user script.
Once installed, the user script hides the entire right-sidebar and extends the Preview Pane to the full width of the screen. Below you can see a preview of it installed.
On the left is the original layout, while the right is the extended preview pane.
Finally, if you want an even more Outlook-style experience in Gmail, disable the conversation grouping by accessing the General tab within Mail Settings and clicking the radio button labeled “Conversation view off.”
Gmail Preview Pane Extend user script works on Chrome and Firefox – with Greasemonkey add-on.
Install: Gmail Preview Pane Extend