A long awaited feature that Google users have desired is the ability to back up and save data externally. Google finally announced support for exporting and backing up your Gmail and Google Calendar data without needing to use third-party software. All you need to do is head to Google’s data download page, which you can visit via the source link, sign into your account, and click “Create an archive.”
You can choose to download everything in your account, or just pick and choose the elements you want to back up. Gmail messages come in .MBOX format, while calendars download in as an .ICAL. In typical Google fashion, this feature will be rolled out over the next month.
Source: Official Gmail Blog