Google is testing Gmail functionality redesign
You've got (new) mail
A stripped-back design of Gmail by Google is said to be in play, which puts the service more in line with Google+, meaning that it could be working across a variety of screen sizes and seamlessly adapting without losing any of its functionality. It also looks as though the new and improved Gmail allows users to reduce the window size whilst keeping Gmail constantly open at the side of their screen.
A new highlighting 'pin' system also appears to have been implemented, which would replace the current 'stars' as a way of keeping track of important emails. The user can use a toggle at the top of the page to drag all 'pinned' emails to the top of the pile.
Google is yet to officially comment on the redesign.