Missive - Team communication app now supporting FB, Twitter & SMS
Mailtrim - Email lives forever!. Reinvigorate your emailing experience with the best free email client, the Mailtrim
Spike - Spike solves businesses' communication chaos by bringing together email, team chat, collaborative docs, and meetings, into one feed.
Hexamail Flow - Hexamail Flow is an email client application for desktop that you can use to manage, send, and receive emails from multiple providers in one unified place.
Front - multi-channel inbox service for collaborative teams
FastMail - Email, calendars, and contacts to highest standards of security, privacy and reliability.