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
Minimize Email - Anonymously tell coworkers when they send too many emails 🙊
mlist - Email newsletters, outside of the inbox
Dispatch - Email parsing for sales leads
HEY - Email at its best, new from Basecamp.
Mailburn - The most handy iPhone email client!