MailStore - MailStore Home - A 100% free single-private-user desktop solution
Hiver - Manage Customer Support, Sales and Projects right from your Gmail inbox. Collaborate with Shared Labels, Shared Contacts, email notes, email reminders and email templates
Gmvault - Backup the emails in your Gmail account.
Clean Email - Clean Email is an online service that empowers you to take control of your mailbox.
Mail Backup X - Your one stop mail backup and archiving tool for Mac.
DuoCircle - DuoCircle provides enterprise spam filtering and email management solutions.