Polymail - Native email app for email productivity.
Roundcube - Web-based IMAP email client
New Gmail - The new version of Gmail web
Mailpile - Mailpile is a modern, fast web-mail client with user-friendly encryption and privacy features.
Airmail for iOS - One of the best Mac email clients, now on iPhone
Mailo - Mailo is an email client where you can send and receive emails to and from anyone with an email address.