MailStore - MailStore Home - A 100% free single-private-user desktop solution
Gmvault - Backup the emails in your Gmail account.
Intradyn Email Archiver - Orca Email Archiver provides email archiving solution for local government and business.
Mail Backup X - Your one stop mail backup and archiving tool for Mac.
Hornetsecurity Email Archiving - Hornetsecurity Email Archiving is one of the advanced software that offers long-term, unchangeable, and secure storage of important company information, data, and flies.
imapsync - Console-based utility for migrating IMAP mailboxes.