imapsync - Console-based utility for migrating IMAP mailboxes.
MailStore - MailStore Home - A 100% free single-private-user desktop solution
MigrationWiz - MigrationWiz provides on-demand mailbox migration services through a fully automated cloud-based...
Gmvault - Backup the emails in your Gmail account.
MailSteward - MailSteward : The Ultimate E-mail Manager for Mac OS X
Fetchmail - The Fetchmail Project