Mailo - Mailo is an email client where you can send and receive emails to and from anyone with an email address.
SendOut - Affordable email marketing for bloggers and influencers
HEY - Email at its best, new from Basecamp.
MailChimp - MailChimp is the best way to design, send, and share email newsletters.
Horde - Horde Groupware is a free, enterprise ready, browser based collaboration suite.
rasa.io - Get more from your email list.