If you use Google Gmail, there is a fantastic utility which allows you to back up all of your e-mails to a folder on your computer. You may wonder, why bother, since Gmail has never deleted any e-mail before, but since Gmail is a free service, there are no guarantees that they will not change that policy in the future and limit the retention period for e-mails.
Gmail Backup can be downloaded by clicking here . The program was last updated late in 2009, but still works perfectly as of December 2012. You simply type in your full Gmail address (YourName@Gmail.com  or if your company hosts its e-mail with Gmail, then YourName@YourCompany.com ) and your e-mail password. Choose a folder to back up the e-mails to on your computer, and select a date range of e-mails to backup.
Click on Backup, and your e-mails will be transferred to the folder you specified. The messages can be opened by any program that reads .eml format. If Gmail ever decides to delete e-mail or you ever lose the e-mails, you can restore them by clicking the restore button.
More information about Gmail Backup is available by clicking here  and is definitely worth the download if you want a simple method for backing up your Gmail messages.