Mailmeteor - Send hundreds of personalized emails with Gmail.
Roundcube - Web-based IMAP email client
GMass - GMass allows you to easily schedule emails, send out mass emails and mail merge campaigns and more with Gmail! Click here to learn about more features!
Mailo - Mailo is an email client where you can send and receive emails to and from anyone with an email address.
Email on Acid - We make the send button safer. For every campaign, every message, and every inbox, Email on Acid has the time-saving tools you need to put your best email forward.
Mailpile - Mailpile is a modern, fast web-mail client with user-friendly encryption and privacy features.