As a long time Gmail fan, every email that I send or receive goes through my gmail account. Once I was annoyed by it's clustered conversations but then it won me over with keyboard shortcuts and amazing search of my inbox.
One thing that does terrify me is their ability to lock you out of your account, taking several days to fix it even if you do the required reset to your password via text message or secondary email. While I have both set up in case of emergencies, I also have a backup.
If you work remotely, you probably have a lot of important details in your inbox. Don't risk getting locked out and immobilized for days while your account is verified again. There are a handful of ways to back up your data. And though I don't see Google going out of business soon, you never ever know when that data will go away.
If you are using Gmail take a few minutes to ensure that your account is setup for easy verification should Google ever decide you're worthy of scrutiny. Go to google.com, at the top right corner there is a settings link, you want to go to your account settings. At the top right of that page there is a link to change your password recovery options. Click that, verify your password and fill out the form.
Thunderbird - This powerful email client is from Mozilla. Why this and not Apple Mail or Outlook? Because it keeps the actual data files small so your hard drive isn't overwhelmed by the size of the backup. Plus I love Thunderbird for offline composing.
To set this up first change your settings in Gmail, you want to enable pop access but leave a copy of all messages in your Gmail account. Save your changes.
Then in Thunderbird, setup a new account. Gmail has handy step by step instructions for this in whatever email client you choose.
After the setup is complete, Thunderbird will download a backup of your account.
Backupify - A great tool that first came to my attention via Twitter, then in conversation with Jason Falls. Backupify will create a remote backup of accounts for you including Twitter, Facebook. LinkedIN and numerous other social media accounts. It'll also backup your Gmail account to a secure server.
I do not personally use it for Gmail backups but it's a great way to handle everything in one place.
Gmail Backup - If you want an additional Windows and Linux option, I haven't tried this but I've heard that it's a good backup tool.
Another Gmail account - You can always create another Gmail account and configure it to download your current account email. It's another backup on Google's system but it's a good place if you don't want to back it up on your computer or a third party service.
Remember to do a backup on schedule. I open Thunderbird before I go to sleep most nights, so much client info and many tasks come into my account during the day and I wouldn't be functional without a full backup. Also, backup THAT backup to an external drive.
Do you have a favorite backup method not mentioned here? Share it in the comments!