OwnBackup - OwnBackup provides automated backups of SaaS and PaaS data and restore tools for disaster recovery.
imapsync - Console-based utility for migrating IMAP mailboxes.
SolarWinds Backup - Modern server backup software
audriga Email and Groupware migration - Easily migrate your email, contacts, calendar items and tasks to your new provider or server. No software installation is required.
Datto Backupify - Protect your business with backup.
MailStore - MailStore Home - A 100% free single-private-user desktop solution