The following highlights Gmail Keeper's features.
Automate the backup to run daily, weekly or monthly, as you want. It's really a big time saver.
Backup both Gmail and Google Apps email
What you need to do is to Input full email address as user name.
Backup Gmail labels
Not only the emails are backed up, but also the labels that associated with emails.
Filter backup by date range, folders or labels
For each backup profile you can choose to backup only emails between a specified date range, or only backup a certain folders or labels.
Multiple account support
Create as many backup profiles as you wish
Restore your backup to Gmail or Google Apps account
Certainly you want to be able to restore your e-mail backup when you have to, without losing the Gmail labels.
Transfer e-mail between any Gmail and Google Apps account
Combine the backup function with restore function, you can migrate your emails between any regular Gmail accounts and Apps account, again, with the labels reserved.
Backup data is stored in open file formats
1. Standard EML files that can be opened by Microsoft Outlook, etc
2. Standard zip archive that can be opened by Winzip, 7-zip, etc
Secure and safe
1. Password protect your backup data
2. Login info is highly encrypted with AES algorithm
3. Connection to Gmail server is protected by SSL
See also using Gmail Keeper