Mailbird is a desktop email client for Windows 7, 8 and 10.

eM Client is a Windows based e-mail client for sending and receiving e-mails, managing calendars, contacts, and tasks.

Airmail is a fast mail client for Mac and iPhone.

Inbox by Gmail is a new app from the Gmail team. Inbox is an organized place to get things done and get back to what matters. Bundles keep emails organized.

Mailspring is a multi-platform email client.

Mailplane is a Gmail client for Mac.