MailStore - MailStore Home - A 100% free single-private-user desktop solution
Thexyz - Secure premium email service with mobile sync apps for calendar, contacts, tasks, notes and FISMA compliant email archiving.
imapsync - Console-based utility for migrating IMAP mailboxes.
ZixArchive - ZixArchive is a cloud-based solution to collect, store and search archived emails.
MozBackup - Backup tool for Firefox and Thunderbird
Cryoserver - Cryoserver is an all-in-one email archiving solution that empowers you to preserve your email in a tamper-evident archive, making you transform your data into a useful archive for everyday use.