If don’t use Gmail, you are with the minority. Google’s email service is undoubtedly the most advanced and user friendly one on the web. It is also very reliable and has a huge disk space. That being said, if you rely on it for all your email communications, it would be a good idea to back it up once in a while right?
For this purpose there is a tool called Gmail Backup. You need to download the software to your computer (Windows or Linux), and it will backup your account with one click.