The document discusses Google's new tabbed inbox layout for Gmail and its impact. It notes newsletters may be sorted into the "Promotions" tab. The changes only affect the Gmail app and desktop versions, not Mailbox or iPhone. While one study found a small reduction in open rates, the document argues more data is needed and notes the importance of optimizing for mobile given its growing use. It recommends marketers adapt to the changes, educate subscribers, and focus on mobile-first design.