imapsync - Console-based utility for migrating IMAP mailboxes.
SolarWinds Backup - Modern server backup software
Gmvault - Backup the emails in your Gmail account.
Druva inSync - Your device may be lost, but your data isn’t with Druva inSync™ Integrated backup, eDiscovery and compliance monitoring.
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.
Datto Backupify - Protect your business with backup.