There are quite some email clients out there, the most popular being Outlook and Thunderbird. This does not necessarily mean that everyone uses these two email clients. There is IncrediMail, Postbox, The Bat, Windows Live Mail, and others. If you want one complete backup solution for all of them, then we have already reviewed MailStore Home, another useful product is MailBrowserBackup.
If you are not satisfied give KLS Mail Backup a try. It is a complete backup solution for all popular email clients out there. It creates both full backup and incremental backup, thus speeding up the backup process.
You can select which items you which to include, apart from the email clients there is also option to backup Internet Explorer, Firefox, Opera, and Seamonkey/Mozilla browsers. Once you select the email clients to backup you will be shown further components on the right side(see screenshot below).
Once you have selected the desired items, click Add and the job will added to the list. You can add multiple jobs, when done, hit Run and they will be executed immediately. You can manually select the output destination by going to properties, the backup is stored in compressed zip archive.
It works on Windows 2000, Windows XP, Windows Vista, and Windows 7. Enjoy!