The Gmail exporting feature is completely new and it will be gradually released next month. It will let you download a big MBOX file you can import in mail clients like Outlook, Thunderbird or Apple Mail. You can also use this feature to backup your Gmail messages and read them offline.
"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," informs Google.