Spark Mail - Spark helps you take your inbox under control. Instantly see what’s important and quickly clean up the rest. Spark for Teams allows you to create, discuss, and share email with your colleagues
Missive - Team communication app now supporting FB, Twitter & SMS
Microsoft Outlook - Organize your world. Outlook’s email and calendar tools help you communicate, stay on top of what matters, and get things done.
Mailtrim - Email lives forever!. Reinvigorate your emailing experience with the best free email client, the Mailtrim
K-9 Mail - K-9 is an opensource email client making it easy to chew through large volumes of email.
Spike - Spike solves businesses' communication chaos by bringing together email, team chat, collaborative docs, and meetings, into one feed.