HOW TO BACK UP YOUR GMAIL:

Under Privacy & personalization, click on “Manage your data & personalization.”
Scroll down to “Download or delete your data.” Click on “Download your data.”

This will take you to the Google Takeout page. Under “Select data to include” check the box next to Gmail and any other apps you want to back up. (Note that some services have buttons labeled “Multiple formats.” Click on that button to choose the format in which your data will be downloaded.) Then click “Next step.

To decide how you want to receive your data, click the arrow underneath “Delivery method” to see your options, including emailing a download link or adding it to your Drive, Dropbox, OneDrive, or Box.

You can also choose whether to export just one time or every two months (for up to a year), and you can choose the type of file and the maximum file size. (If the file size is larger than your maximum, it will be separated into multiple flies; and any files larger than 2GB will use the zip64 compression format.) After you’re done making your selections, click “Create export

Your export will start. Be prepared to wait; it might take days to finish. You can also click “Cancel export” or “Create another export.”