imapsync - Console-based utility for migrating IMAP mailboxes.
MultCloud - Multiple Cloud Storage Manager: Migrate, move, sync, copy, backup and transfer cloud files with MultCloud, which supports Dropbox, Box, Google Drive, Mega, OneDrive and FTP, etc.
Gmvault - Backup the emails in your Gmail account.
Cloud Combine - Cloud Combine is a browser and manager for the cloud services.
Cryoserver - Cryoserver is an all-in-one email archiving solution that empowers you to preserve your email in a tamper-evident archive, making you transform your data into a useful archive for everyday use.
Apigee - Intelligent and complete API platform