SpamHero - SpamHero is a professional spam filtering accuracy while lowering the cost to domain and business owners.
imapsync - Console-based utility for migrating IMAP mailboxes.
SpamAssassin - Use this program to "Unspam" your mailbox(es).
Gmvault - Backup the emails in your Gmail account.
SpamTitan - Comprehensive Email Protection. 99.99% Spam Detection. Blocks phishing, viruses, malware and other email threats.
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.