Gmvault - Backup the emails in your Gmail account.
MailStore - MailStore Home - A 100% free single-private-user desktop solution
Datto Backupify - Protect your business with backup.
MailSteward - MailSteward : The Ultimate E-mail Manager for Mac OS X
Mail Backup X - Your one stop mail backup and archiving tool for Mac.
Beyond Inbox - Beyond Inbox, backup tool to backup, copy, move and restore email messages of your IMAP account...