Having access to your data and being able to take it with you is important, especially if that data contains precious memories like old love letters, your first job offer, or that 100-message thread discussing the merits of various cat videos. Starting today we’re rolling out the ability to export a copy of your Gmail and Google Calendar data, making it easy to back up your data or move to another service.
You can download all of your mail and calendars or choose a subset of labels and calendars. You can also download a single archive file for multiple products with a copy of your Gmail, Calendar, Google+, YouTube, Drive, and other Google data.
The ability to download your Gmail messages will be rolled out over the next month while Calendar data is available to download for everyone today.
https://gmail.googleblog.com/2013/12/download-copy-of-your-gmail-and-google.html