Clean Email - Clean Email is an online service that empowers you to take control of your mailbox.
Missive - Team communication app now supporting FB, Twitter & SMS
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
Spike - Spike solves businesses' communication chaos by bringing together email, team chat, collaborative docs, and meetings, into one feed.
MailClark - The Slack bot for external communications
Mailtrim - Email lives forever!. Reinvigorate your emailing experience with the best free email client, the Mailtrim