Although many handy features like automatic message translation have been part of Gmail Labs for a while now, Google has decided to graduate it and a couple of others to official Gmail features. Automatic Message Translation works by providing you with a translate button for any message that Google believes to be in your non-default language.
If your default is English, Gmail will assume that's what you want but you can switch it to any other language you prefer from a drop-down menu next to the translate button in your email.
In addition to built-in translating, Google has tweaked the page title to make it easier to see how many unread messages you have waiting, and it has graduated the "Smart Mute" lab that helps keep noisy email threads from cluttering up your inbox. A few classic Gmail labs have been retired as well. Hit up the full post over at the Official Gmail Blog for details.
Say hello (or olá or halo or salam) to automatic message translation in Gmail [Official Gmail Blog]