Cypht - All your E-mail, from all your accounts, in one place. Cypht is like a news reader, but for E-mail.
Roundcube - Web-based IMAP email client
Mailpile - Mailpile is a modern, fast web-mail client with user-friendly encryption and privacy features.
Mailo - Mailo is an email client where you can send and receive emails to and from anyone with an email address.
HEY - Email at its best, new from Basecamp.
Soverin - Soverin is the honest email service that doesn’t sell your data.