Flow-e is a visualization layer on top of your Gmail or Outlook inbox. It provides an elegant Kanban-like workflow that's combined with the ideas behind Inbox Zero and GTD. Flow-e eliminates the need of external task management tools and transforms your inbox into a central To Do app.
KanbanMail - A Kanban board for your emails.
Canary Mail - Privacy-aware email app for Mac & iOS
Sortd - Rated the #1 App for Gmail
Airmail - Airmail is a lightweight and lightning fast mail client for Mac.
Drag for Gmail - Transform Gmail into organized To Do lists (like Trello)
Polymail - Native email app for email productivity.