Acronis Backup and Recovery - Acronis Backup is a data recovery solution that offers more ways of storing and recovering drives, folders and files as compared to other similar solutions.
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.
SolarWinds Backup - Modern server backup software
imapsync - Console-based utility for migrating IMAP mailboxes.
Backup Exec - Backup Exec provides simple, complete backup and recovery protection for your business, to cover all data wherever it resides. Try free for 60 days.
Gmvault - Backup the emails in your Gmail account.