Missive - Team communication app now supporting FB, Twitter & SMS
imapsync - Console-based utility for migrating IMAP mailboxes.
Spike - Spike solves businesses' communication chaos by bringing together email, team chat, collaborative docs, and meetings, into one feed.
Gmvault - Backup the emails in your Gmail account.
Mailtrim - Email lives forever!. Reinvigorate your emailing experience with the best free email client, the Mailtrim
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.