OwnBackup - OwnBackup provides automated backups of SaaS and PaaS data and restore tools for disaster recovery.
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
Gmvault - Backup the emails in your Gmail account.
Datto Backupify - Protect your business with backup.
imapsync - Console-based utility for migrating IMAP mailboxes.