Google Takeout (Google Takeaway in some languages) is a project by the Google Data Liberation Front that allows users of Google products, such as YouTube and Gmail, to export their data to a downloadable ZIP file.
To Download your Data Log in to the account you wish to backup and click on the URL below.
Gmail Account is downloaded in MBOX format which can be opened and viewed in Mozilla Thunderbird
To import the MBOX file in Thunderbird you will need to download the following add on https://addons.mozilla.org/en-US/thunderbird/addon/importexporttools/
Once the add on is included in Thunderbird:
Click on the menu in the top right hand corner
Select tools>ImportExportTools>import mbox file
Select 'import directly one or more mbox file' and then select your mbox file from its saved location and click 'open'.