Sure, you can open elaborately-crafted email using Gmail on your phone, but that doesn’t mean you want to. Most web-based messages are formatted for the desktop, and Gmail doesn’t tweak them to fit the confines of a mobile screen. Mercifully, you won’t have to squint quite so much in the days ahead: Google is introducing support for responsive design in Gmail before the end of September. If a message supports the adaptive technology, Google’s email app will automatically resize it to help you read the contents and tap links. You won’t notice the upgrade with every message, but it should give you more incentive to deal with a message right away instead of waiting until you’re at your computer.
Source: Official Gmail Blog