You can see the same emails on your phone as you can on your computer using Gmail, but these devices have a number of fundamental differences. The way emails render on a large screen device won't always make sense on a smaller one, so Google is getting ready to implement responsive design for emails in Gmail.
Responsive email design means the layout will be optimized for your device. Buttons and links will be large enough to hit on your phone, and content will be spaced more appropriately. This isn't only about making email better on phones. Even on desktops you'll see some improvements as emails formatted for mobile will look better on a large display.
Importantly, this only applies to emails with proper CSS media queries in their design. Google has some help documents for email designers to familiarize themselves with the system. This change will roll out later this month, presumably as an update to the Gmail app. We'll get you an APK as soon as that shows up.
- Gmail Blog