KLS Mail Backup is a FREE for personal use program which lets you backup and restore your mail account and other settings in Windows Mail, Outlook Express, Mozilla, Thunderbird and you can even backup your firefox profiles with this tool.
This utlity is again multipurpose as it not only allows you to backup the settings of your email clients for free but it does allows you to do more by backing up settings of the your favourite browsers including firefox, internet explorer and opera.