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.
After selecting which program settings you want to backup you can further select what all you want to backup in the selected program. (as shown in the image below if you select Internet Explorer)
In all this is one the best and simple to use program to take the backup and restore the backups when ever needed for all the programs shown in the above image,
As far as the requirements are concerned for this small program, it will require only 10 MB of free space for installation and around 64 MB of memory to run and it will run in all the versions of windows from 2000 till windows vista.