From Silvawood Software:
Offsiter is a backup utility that compresses files and sends them as encrypted attachments to off-site e-mail accounts. Storing files away from your home or business premises is far more secure than relying on conventional archiving mechanisms such as CD-ROM, tapes, and hard drives, all of which are prone to theft, damage, or local acts of God. You can use any e-mail account to store your files, including the free ones provided by Yahoo, Microsoft, and Google. Offsiter can use archives created with any other compression application. However, Offsiter's own compression utility does offer you the option to archive only those files that have changed since they were last backed up. This drastically reduces the size of subsequent archives.