Why mail backup?
You may have your favorite personal family and friends photos in your mail or any important data of your business in it. its better be save to backup them. Another feature of this is you can read your old mails offline too.
Gmail-Backup This Gmail-backup is a free gmail backup tool that you can use to backup all your emails to .eml format and store it in your PC and there by makes it accessible to you Via Outlook Express or Thunderbird when you need your mails back.
This Software tool is provided in Windows and Linux platform for now and then it will be ex-tented to other platforms soon. A small think you have to do before backup is to enable POP/IMAP option on your gmail settings.
First time you backup all the mails in your Gmail box and after that for every email backup use the option newest mail only so that you no need to backup every mail again.
one disadvantage with this is the manual backup, there is no automatic backup feature available as per now in the pre-final release. hope this will be added in the final release.
many email backup softwares and backup services are available which cost you more this quick alternative free to use backup feature will be helpful for all. download gmail-backup
source