Gmvault
From Attie's Wiki
G-Mail backup utility
Package Dependencies
apt-get install python-setuptools python-virtualenv easy_install -U distribute
Install
virtualenv --no-site-packages gmvault cd gmvault pip install --verbose --pre gmvault --allow-external IMAPClient
Run
./gmvault sync -d ${ARCHIVE_DIR} -c no --no-compression ${EMAIL_ADDR}
The first time you will need to authenticate the application.