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.
Saleshandy is a cold email platform that helps organizations increase their email outreach operations without sacrificing quality. On Saleshandy, you can send hundreds (or thousands) of campaigns with multi-stage automated follow-up emails to your leads at once. You can use merge tags to customize your email campaigns and have automated follow-ups delivered based on the previous email's interaction (opens or clicks).
KanbanMail - A Kanban board for your emails.
Gmelius - Gmelius is the first collaboration platform designed for G Suite and your company's daily tools.
Sortd - Rated the #1 App for Gmail
Mailtrack.io - The best email tracking solution I've found. Free
Drag for Gmail - Transform Gmail into organized To Do lists (like Trello)
Yesware - Sell smarter with email tracking and more