Gmvault - Backup the emails in your Gmail account.
imapsync - Console-based utility for migrating IMAP mailboxes.
Datto Backupify - Protect your business with backup.
iSync - iSync is a software application published by Apple Inc.
MailStore - MailStore Home - A 100% free single-private-user desktop solution
OfflineIMAP - OfflineImap synchronizes email between an IMAP server and a MailDir or between two IMAP servers.