Klaviyo - Klaviyo helps brands own the customer experience, grow higher-value relationships, and deliver more personalized marketing experiences across email, mobile, and web.
mailcow - An open source mailserver suite.
TargetBay - TargetBay is a complete eCommerce revenue generation platform.
SmarterMail - SmarterMail is a next generation email management server that is offering several business collaboration and communication features as well.
Campaign Monitor - Email marketing software built for designers and their clients to run successful email campaigns.
hMail Server - hMailServer is a free e-mail server for Microsoft Windows.