I’ve used SysCloudSoft’s on premise backup and found it very useful. The
software provides a backup for unlimited Google Apps data with a single
click.Scheduled incremental backups are also possible every 1 hr. The software
is secure with 512 bit encryption and users can view their emails in Outlook or
Thunderbird.

The best advantage is that personal users can backup unlimited Google Apps
Data for FREE – Gmail, Google Docs,Contacts,Calendar,Sites. For businesses it
starts at $399